Bump to v0.3.0

.gitlab-ci.yml

@@ -25,6 +25,8 @@ build-debug:
     - mkdir ./artifacts
     - mv ./AMWD.Protocols.Modbus.Common/bin/Debug/*.nupkg    ./artifacts/
     - mv ./AMWD.Protocols.Modbus.Common/bin/Debug/*.snupkg   ./artifacts/
+    - mv ./AMWD.Protocols.Modbus.Proxy/bin/Debug/*.nupkg     ./artifacts/
+    - mv ./AMWD.Protocols.Modbus.Proxy/bin/Debug/*.snupkg    ./artifacts/
     - mv ./AMWD.Protocols.Modbus.Serial/bin/Debug/*.nupkg    ./artifacts/
     - mv ./AMWD.Protocols.Modbus.Serial/bin/Debug/*.snupkg   ./artifacts/
     - mv ./AMWD.Protocols.Modbus.Tcp/bin/Debug/*.nupkg       ./artifacts/
@@ -80,6 +82,8 @@ build-release:
     - mkdir ./artifacts
     - mv ./AMWD.Protocols.Modbus.Common/bin/Release/*.nupkg    ./artifacts/
     - mv ./AMWD.Protocols.Modbus.Common/bin/Release/*.snupkg   ./artifacts/
+    - mv ./AMWD.Protocols.Modbus.Proxy/bin/Release/*.nupkg     ./artifacts/
+    - mv ./AMWD.Protocols.Modbus.Proxy/bin/Release/*.snupkg    ./artifacts/
     - mv ./AMWD.Protocols.Modbus.Serial/bin/Release/*.nupkg    ./artifacts/
     - mv ./AMWD.Protocols.Modbus.Serial/bin/Release/*.snupkg   ./artifacts/
     - mv ./AMWD.Protocols.Modbus.Tcp/bin/Release/*.nupkg       ./artifacts/

AMWD.Protocols.Modbus.Common/Contracts/ModbusClientBase.cs

@@ -52,7 +52,7 @@ namespace AMWD.Protocols.Modbus.Common.Contracts
 		/// <remarks>
 		/// The default protocol used by the client should be initialized in the constructor.
 		/// </remarks>
-		public abstract IModbusProtocol Protocol { get; set; }
+		public virtual IModbusProtocol Protocol { get; set; }
 
 		/// <summary>
 		/// Reads multiple <see cref="Coil"/>s.

AMWD.Protocols.Modbus.Common/Utils/AsyncQueue.cs

@@ -45,7 +45,7 @@ namespace System.Collections.Generic
 					internalDequeueTcs = ResetToken(ref _dequeueTcs);
 				}
 
-				await WaitAsync(internalDequeueTcs, cancellationToken).ConfigureAwait(false);
+				await WaitAsync(internalDequeueTcs, cancellationToken);
 			}
 		}
 
@@ -113,7 +113,7 @@ namespace System.Collections.Generic
 		{
 			if (await Task.WhenAny(tcs.Task, Task.Delay(-1, cancellationToken)) == tcs.Task)
 			{
-				await tcs.Task.ConfigureAwait(false);
+				await tcs.Task;
 				return;
 			}
 

AMWD.Protocols.Modbus.Proxy/AMWD.Protocols.Modbus.Proxy.csproj

@@ -0,0 +1,42 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFrameworks>netstandard2.0;net6.0;net8.0</TargetFrameworks>
+    <LangVersion>12.0</LangVersion>
+
+    <PackageId>AMWD.Protocols.Modbus.Proxy</PackageId>
+    <AssemblyName>amwd-modbus-proxy</AssemblyName>
+    <RootNamespace>AMWD.Protocols.Modbus.Proxy</RootNamespace>
+
+    <Product>Modbus Proxy Clients</Product>
+    <Description>Plugging Modbus Servers and Clients together to create Modbus Proxies.</Description>
+    <PackageTags>Modbus Protocol Proxy</PackageTags>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="../AMWD.Protocols.Modbus.Common/Extensions/ArrayExtensions.cs" Link="Extensions/ArrayExtensions.cs" />
+    <Compile Include="../AMWD.Protocols.Modbus.Tcp/Extensions/StreamExtensions.cs" Link="Extensions/StreamExtensions.cs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <None Include="README.md" Pack="true" PackagePath="/" />
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
+    <PackageReference Include="System.IO.Ports" Version="4.7.0" />
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFramework)' == 'net6.0'">
+    <PackageReference Include="System.IO.Ports" Version="6.0.0" />
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFramework)' == 'net8.0'">
+    <PackageReference Include="System.IO.Ports" Version="8.0.0" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\AMWD.Protocols.Modbus.Common\AMWD.Protocols.Modbus.Common.csproj" />
+    <ProjectReference Include="..\AMWD.Protocols.Modbus.Serial\AMWD.Protocols.Modbus.Serial.csproj" />
+  </ItemGroup>
+
+</Project>

AMWD.Protocols.Modbus.Proxy/ModbusRtuProxy.cs

@@ -0,0 +1,867 @@
+using System;
+using System.Collections.Generic;
+using System.IO.Ports;
+using System.Linq;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+using AMWD.Protocols.Modbus.Common;
+using AMWD.Protocols.Modbus.Common.Contracts;
+using AMWD.Protocols.Modbus.Common.Protocols;
+using AMWD.Protocols.Modbus.Serial;
+
+namespace AMWD.Protocols.Modbus.Proxy
+{
+	/// <summary>
+	/// Implements a Modbus serial line RTU server proxying all requests to a Modbus client of choice.
+	/// </summary>
+	public class ModbusRtuProxy : IDisposable
+	{
+		#region Fields
+
+		private bool _isDisposed;
+
+		private readonly SerialPort _serialPort;
+		private CancellationTokenSource _stopCts;
+
+		#endregion Fields
+
+		#region Constructors
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="ModbusRtuProxy"/> class.
+		/// </summary>
+		/// <param name="client">The <see cref="ModbusClientBase"/> used to request the remote device, that should be proxied.</param>
+		/// <param name="portName">The name of the serial port to use.</param>
+		/// <param name="baudRate">The baud rate of the serial port (Default: 19.200).</param>
+		public ModbusRtuProxy(ModbusClientBase client, string portName, BaudRate baudRate = BaudRate.Baud19200)
+		{
+			Client = client ?? throw new ArgumentNullException(nameof(client));
+
+			if (string.IsNullOrWhiteSpace(portName))
+				throw new ArgumentNullException(nameof(portName));
+
+			if (!Enum.IsDefined(typeof(BaudRate), baudRate))
+				throw new ArgumentOutOfRangeException(nameof(baudRate));
+
+			if (!ModbusSerialClient.AvailablePortNames.Contains(portName))
+				throw new ArgumentException($"The serial port ({portName}) is not available.", nameof(portName));
+
+			_serialPort = new SerialPort
+			{
+				PortName = portName,
+				BaudRate = (int)baudRate,
+				Handshake = Handshake.None,
+				DataBits = 8,
+				ReadTimeout = 1000,
+				RtsEnable = false,
+				StopBits = StopBits.One,
+				WriteTimeout = 1000,
+				Parity = Parity.Even
+			};
+		}
+
+		#endregion Constructors
+
+		#region Properties
+
+		/// <summary>
+		/// Gets the Modbus client used to request the remote device, that should be proxied.
+		/// </summary>
+		public ModbusClientBase Client { get; }
+
+		/// <inheritdoc cref="SerialPort.PortName"/>
+		public string PortName => _serialPort.PortName;
+
+		/// <summary>
+		/// Gets or sets the baud rate of the serial port.
+		/// </summary>
+		public BaudRate BaudRate
+		{
+			get => (BaudRate)_serialPort.BaudRate;
+			set => _serialPort.BaudRate = (int)value;
+		}
+
+		/// <inheritdoc cref="SerialPort.Handshake"/>
+		public Handshake Handshake
+		{
+			get => _serialPort.Handshake;
+			set => _serialPort.Handshake = value;
+		}
+
+		/// <inheritdoc cref="SerialPort.DataBits"/>
+		public int DataBits
+		{
+			get => _serialPort.DataBits;
+			set => _serialPort.DataBits = value;
+		}
+
+		/// <inheritdoc cref="SerialPort.IsOpen"/>
+		public bool IsOpen => _serialPort.IsOpen;
+
+		/// <summary>
+		/// Gets or sets the <see cref="TimeSpan"/> before a time-out occurs when a read operation does not finish.
+		/// </summary>
+		public TimeSpan ReadTimeout
+		{
+			get => TimeSpan.FromMilliseconds(_serialPort.ReadTimeout);
+			set => _serialPort.ReadTimeout = (int)value.TotalMilliseconds;
+		}
+
+		/// <inheritdoc cref="SerialPort.RtsEnable"/>
+		public bool RtsEnable
+		{
+			get => _serialPort.RtsEnable;
+			set => _serialPort.RtsEnable = value;
+		}
+
+		/// <inheritdoc cref="SerialPort.StopBits"/>
+		public StopBits StopBits
+		{
+			get => _serialPort.StopBits;
+			set => _serialPort.StopBits = value;
+		}
+
+		/// <summary>
+		/// Gets or sets the <see cref="TimeSpan"/> before a time-out occurs when a write operation does not finish.
+		/// </summary>
+		public TimeSpan WriteTimeout
+		{
+			get => TimeSpan.FromMilliseconds(_serialPort.WriteTimeout);
+			set => _serialPort.WriteTimeout = (int)value.TotalMilliseconds;
+		}
+
+		/// <inheritdoc cref="SerialPort.Parity"/>
+		public Parity Parity
+		{
+			get => _serialPort.Parity;
+			set => _serialPort.Parity = value;
+		}
+
+		#endregion Properties
+
+		#region Control Methods
+
+		/// <summary>
+		/// Starts the server.
+		/// </summary>
+		/// <param name="cancellationToken">A cancellation token used to propagate notification that this operation should be canceled.</param>
+		public Task StartAsync(CancellationToken cancellationToken = default)
+		{
+			Assertions();
+
+			_stopCts?.Cancel();
+			_serialPort.Close();
+			_serialPort.DataReceived -= OnDataReceived;
+
+			_stopCts?.Dispose();
+			_stopCts = new CancellationTokenSource();
+
+			_serialPort.DataReceived += OnDataReceived;
+			_serialPort.Open();
+
+			return Task.CompletedTask;
+		}
+
+		/// <summary>
+		/// Stops the server.
+		/// </summary>
+		/// <param name="cancellationToken">A cancellation token used to propagate notification that this operation should be canceled.</param>
+		public Task StopAsync(CancellationToken cancellationToken = default)
+		{
+			Assertions();
+			return StopAsyncInternal(cancellationToken);
+		}
+
+		private Task StopAsyncInternal(CancellationToken cancellationToken)
+		{
+			_stopCts.Cancel();
+
+			_serialPort.Close();
+			_serialPort.DataReceived -= OnDataReceived;
+
+			return Task.CompletedTask;
+		}
+
+		/// <summary>
+		/// Releases all managed and unmanaged resources used by the <see cref="ModbusRtuProxy"/>.
+		/// </summary>
+		public void Dispose()
+		{
+			if (_isDisposed)
+				return;
+
+			_isDisposed = true;
+
+			StopAsyncInternal(CancellationToken.None).Wait();
+
+			_serialPort.Dispose();
+			_stopCts?.Dispose();
+		}
+
+		private void Assertions()
+		{
+#if NET8_0_OR_GREATER
+			ObjectDisposedException.ThrowIf(_isDisposed, this);
+#else
+			if (_isDisposed)
+				throw new ObjectDisposedException(GetType().FullName);
+#endif
+		}
+
+		#endregion Control Methods
+
+		#region Client Handling
+
+		private void OnDataReceived(object _, SerialDataReceivedEventArgs evArgs)
+		{
+			try
+			{
+				var requestBytes = new List<byte>();
+				do
+				{
+					byte[] buffer = new byte[RtuProtocol.MAX_ADU_LENGTH];
+					int count = _serialPort.Read(buffer, 0, buffer.Length);
+					requestBytes.AddRange(buffer.Take(count));
+
+					_stopCts.Token.ThrowIfCancellationRequested();
+				}
+				while (_serialPort.BytesToRead > 0);
+
+				_stopCts.Token.ThrowIfCancellationRequested();
+				byte[] responseBytes = HandleRequest([.. requestBytes]);
+				if (responseBytes == null)
+					return;
+
+				_stopCts.Token.ThrowIfCancellationRequested();
+				_serialPort.Write(responseBytes, 0, responseBytes.Length);
+			}
+			catch
+			{ /* keep it quiet */ }
+		}
+
+		#endregion Client Handling
+
+		#region Request Handling
+
+		private byte[] HandleRequest(byte[] requestBytes)
+		{
+			byte[] recvCrc = requestBytes.Skip(requestBytes.Length - 2).ToArray();
+			byte[] calcCrc = RtuProtocol.CRC16(requestBytes, 0, requestBytes.Length - 2);
+			if (!recvCrc.SequenceEqual(calcCrc))
+				return null;
+
+			switch ((ModbusFunctionCode)requestBytes[1])
+			{
+				case ModbusFunctionCode.ReadCoils:
+					return HandleReadCoilsAsync(requestBytes, _stopCts.Token).Result;
+
+				case ModbusFunctionCode.ReadDiscreteInputs:
+					return HandleReadDiscreteInputsAsync(requestBytes, _stopCts.Token).Result;
+
+				case ModbusFunctionCode.ReadHoldingRegisters:
+					return HandleReadHoldingRegistersAsync(requestBytes, _stopCts.Token).Result;
+
+				case ModbusFunctionCode.ReadInputRegisters:
+					return HandleReadInputRegistersAsync(requestBytes, _stopCts.Token).Result;
+
+				case ModbusFunctionCode.WriteSingleCoil:
+					return HandleWriteSingleCoilAsync(requestBytes, _stopCts.Token).Result;
+
+				case ModbusFunctionCode.WriteSingleRegister:
+					return HandleWriteSingleRegisterAsync(requestBytes, _stopCts.Token).Result;
+
+				case ModbusFunctionCode.WriteMultipleCoils:
+					return HandleWriteMultipleCoilsAsync(requestBytes, _stopCts.Token).Result;
+
+				case ModbusFunctionCode.WriteMultipleRegisters:
+					return HandleWriteMultipleRegistersAsync(requestBytes, _stopCts.Token).Result;
+
+				case ModbusFunctionCode.EncapsulatedInterface:
+					return HandleEncapsulatedInterfaceAsync(requestBytes, _stopCts.Token).Result;
+
+				default: // unknown function
+					{
+						byte[] responseBytes = new byte[5];
+						Array.Copy(requestBytes, 0, responseBytes, 0, 2);
+
+						// Mark as error
+						responseBytes[1] |= 0x80;
+
+						responseBytes[2] = (byte)ModbusErrorCode.IllegalFunction;
+
+						SetCrc(responseBytes);
+						return responseBytes;
+					}
+			}
+		}
+
+		private async Task<byte[]> HandleReadCoilsAsync(byte[] requestBytes, CancellationToken cancellationToken)
+		{
+			if (requestBytes.Length < 8)
+				return null;
+
+			byte unitId = requestBytes[0];
+			ushort firstAddress = requestBytes.GetBigEndianUInt16(2);
+			ushort count = requestBytes.GetBigEndianUInt16(4);
+
+			var responseBytes = new List<byte>();
+			responseBytes.AddRange(requestBytes.Take(2));
+			try
+			{
+				var coils = await Client.ReadCoilsAsync(unitId, firstAddress, count, cancellationToken);
+
+				byte[] values = new byte[(int)Math.Ceiling(coils.Count / 8.0)];
+				for (int i = 0; i < coils.Count; i++)
+				{
+					if (coils[i].Value)
+					{
+						int byteIndex = i / 8;
+						int bitIndex = i % 8;
+
+						values[byteIndex] |= (byte)(1 << bitIndex);
+					}
+				}
+
+				responseBytes.Add((byte)values.Length);
+				responseBytes.AddRange(values);
+			}
+			catch
+			{
+				responseBytes[1] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+			}
+
+			AddCrc(responseBytes);
+			return [.. responseBytes];
+		}
+
+		private async Task<byte[]> HandleReadDiscreteInputsAsync(byte[] requestBytes, CancellationToken cancellationToken)
+		{
+			if (requestBytes.Length < 8)
+				return null;
+
+			byte unitId = requestBytes[0];
+			ushort firstAddress = requestBytes.GetBigEndianUInt16(2);
+			ushort count = requestBytes.GetBigEndianUInt16(4);
+
+			var responseBytes = new List<byte>();
+			responseBytes.AddRange(requestBytes.Take(2));
+			try
+			{
+				var discreteInputs = await Client.ReadDiscreteInputsAsync(unitId, firstAddress, count, cancellationToken);
+
+				byte[] values = new byte[(int)Math.Ceiling(discreteInputs.Count / 8.0)];
+				for (int i = 0; i < discreteInputs.Count; i++)
+				{
+					if (discreteInputs[i].Value)
+					{
+						int byteIndex = i / 8;
+						int bitIndex = i % 8;
+
+						values[byteIndex] |= (byte)(1 << bitIndex);
+					}
+				}
+
+				responseBytes.Add((byte)values.Length);
+				responseBytes.AddRange(values);
+			}
+			catch
+			{
+				responseBytes[1] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+			}
+
+			AddCrc(responseBytes);
+			return [.. responseBytes];
+		}
+
+		private async Task<byte[]> HandleReadHoldingRegistersAsync(byte[] requestBytes, CancellationToken cancellationToken)
+		{
+			if (requestBytes.Length < 8)
+				return null;
+
+			byte unitId = requestBytes[0];
+			ushort firstAddress = requestBytes.GetBigEndianUInt16(2);
+			ushort count = requestBytes.GetBigEndianUInt16(4);
+
+			var responseBytes = new List<byte>();
+			responseBytes.AddRange(requestBytes.Take(2));
+			try
+			{
+				var holdingRegisters = await Client.ReadHoldingRegistersAsync(unitId, firstAddress, count, cancellationToken);
+
+				byte[] values = new byte[holdingRegisters.Count * 2];
+				for (int i = 0; i < holdingRegisters.Count; i++)
+				{
+					values[i * 2] = holdingRegisters[i].HighByte;
+					values[i * 2 + 1] = holdingRegisters[i].LowByte;
+				}
+
+				responseBytes.Add((byte)values.Length);
+				responseBytes.AddRange(values);
+			}
+			catch
+			{
+				responseBytes[1] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+			}
+
+			AddCrc(responseBytes);
+			return [.. responseBytes];
+		}
+
+		private async Task<byte[]> HandleReadInputRegistersAsync(byte[] requestBytes, CancellationToken cancellationToken)
+		{
+			if (requestBytes.Length < 8)
+				return null;
+
+			byte unitId = requestBytes[0];
+			ushort firstAddress = requestBytes.GetBigEndianUInt16(2);
+			ushort count = requestBytes.GetBigEndianUInt16(4);
+
+			var responseBytes = new List<byte>();
+			responseBytes.AddRange(requestBytes.Take(2));
+			try
+			{
+				var inputRegisters = await Client.ReadInputRegistersAsync(unitId, firstAddress, count, cancellationToken);
+
+				byte[] values = new byte[count * 2];
+				for (int i = 0; i < count; i++)
+				{
+					values[i * 2] = inputRegisters[i].HighByte;
+					values[i * 2 + 1] = inputRegisters[i].LowByte;
+				}
+
+				responseBytes.Add((byte)values.Length);
+				responseBytes.AddRange(values);
+			}
+			catch
+			{
+				responseBytes[1] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+			}
+
+			AddCrc(responseBytes);
+			return [.. responseBytes];
+		}
+
+		private async Task<byte[]> HandleWriteSingleCoilAsync(byte[] requestBytes, CancellationToken cancellationToken)
+		{
+			if (requestBytes.Length < 8)
+				return null;
+
+			var responseBytes = new List<byte>();
+			responseBytes.AddRange(requestBytes.Take(2));
+
+			ushort address = requestBytes.GetBigEndianUInt16(2);
+
+			if (requestBytes[4] != 0x00 && requestBytes[4] != 0xFF)
+			{
+				responseBytes[1] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.IllegalDataValue);
+
+				AddCrc(responseBytes);
+				return [.. responseBytes];
+			}
+
+			try
+			{
+				var coil = new Coil
+				{
+					Address = address,
+					HighByte = requestBytes[4],
+					LowByte = requestBytes[5],
+				};
+
+				bool isSuccess = await Client.WriteSingleCoilAsync(requestBytes[0], coil, cancellationToken);
+				if (isSuccess)
+				{
+					// Response is an echo of the request
+					responseBytes.AddRange(requestBytes.Skip(2).Take(4));
+				}
+				else
+				{
+					responseBytes[1] |= 0x80;
+					responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+				}
+			}
+			catch
+			{
+				responseBytes[1] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+			}
+
+			AddCrc(responseBytes);
+			return [.. responseBytes];
+		}
+
+		private async Task<byte[]> HandleWriteSingleRegisterAsync(byte[] requestBytes, CancellationToken cancellationToken)
+		{
+			if (requestBytes.Length < 8)
+				return null;
+
+			var responseBytes = new List<byte>();
+			responseBytes.AddRange(requestBytes.Take(2));
+
+			ushort address = requestBytes.GetBigEndianUInt16(2);
+			try
+			{
+				var register = new HoldingRegister
+				{
+					Address = address,
+					HighByte = requestBytes[4],
+					LowByte = requestBytes[5]
+				};
+
+				bool isSuccess = await Client.WriteSingleHoldingRegisterAsync(requestBytes[0], register, cancellationToken);
+				if (isSuccess)
+				{
+					// Response is an echo of the request
+					responseBytes.AddRange(requestBytes.Skip(2).Take(4));
+				}
+				else
+				{
+					responseBytes[1] |= 0x80;
+					responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+				}
+			}
+			catch
+			{
+				responseBytes[1] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+			}
+
+			AddCrc(responseBytes);
+			return [.. responseBytes];
+		}
+
+		private async Task<byte[]> HandleWriteMultipleCoilsAsync(byte[] requestBytes, CancellationToken cancellationToken)
+		{
+			if (requestBytes.Length < 9)
+				return null;
+
+			var responseBytes = new List<byte>();
+			responseBytes.AddRange(requestBytes.Take(2));
+
+			ushort firstAddress = requestBytes.GetBigEndianUInt16(2);
+			ushort count = requestBytes.GetBigEndianUInt16(4);
+
+			int byteCount = (int)Math.Ceiling(count / 8.0);
+			if (requestBytes.Length < 9 + byteCount)
+			{
+				responseBytes[1] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.IllegalDataValue);
+
+				AddCrc(responseBytes);
+				return [.. responseBytes];
+			}
+
+			try
+			{
+				int baseOffset = 7;
+				var coils = new List<Coil>();
+				for (int i = 0; i < count; i++)
+				{
+					int bytePosition = i / 8;
+					int bitPosition = i % 8;
+
+					ushort address = (ushort)(firstAddress + i);
+					bool value = (requestBytes[baseOffset + bytePosition] & (1 << bitPosition)) > 0;
+
+					coils.Add(new Coil
+					{
+						Address = address,
+						HighByte = value ? (byte)0xFF : (byte)0x00
+					});
+				}
+
+				bool isSuccess = await Client.WriteMultipleCoilsAsync(requestBytes[0], coils, cancellationToken);
+				if (isSuccess)
+				{
+					// Response is an echo of the request
+					responseBytes.AddRange(requestBytes.Skip(2).Take(4));
+				}
+				else
+				{
+					responseBytes[1] |= 0x80;
+					responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+				}
+			}
+			catch
+			{
+				responseBytes[1] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+			}
+
+			AddCrc(responseBytes);
+			return [.. responseBytes];
+		}
+
+		private async Task<byte[]> HandleWriteMultipleRegistersAsync(byte[] requestBytes, CancellationToken cancellationToken)
+		{
+			if (requestBytes.Length < 9)
+				return null;
+
+			var responseBytes = new List<byte>();
+			responseBytes.AddRange(requestBytes.Take(8));
+
+			ushort firstAddress = requestBytes.GetBigEndianUInt16(2);
+			ushort count = requestBytes.GetBigEndianUInt16(4);
+
+			int byteCount = count * 2;
+			if (requestBytes.Length < 9 + byteCount)
+			{
+				responseBytes[1] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.IllegalDataValue);
+
+				AddCrc(responseBytes);
+				return [.. responseBytes];
+			}
+
+			try
+			{
+				int baseOffset = 7;
+				var list = new List<HoldingRegister>();
+				for (int i = 0; i < count; i++)
+				{
+					ushort address = (ushort)(firstAddress + i);
+
+					list.Add(new HoldingRegister
+					{
+						Address = address,
+						HighByte = requestBytes[baseOffset + i * 2],
+						LowByte = requestBytes[baseOffset + i * 2 + 1]
+					});
+
+					bool isSuccess = await Client.WriteMultipleHoldingRegistersAsync(requestBytes[0], list, cancellationToken);
+					if (isSuccess)
+					{
+						// Response is an echo of the request
+						responseBytes.AddRange(requestBytes.Skip(2).Take(4));
+					}
+					else
+					{
+						responseBytes[1] |= 0x80;
+						responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+					}
+				}
+			}
+			catch
+			{
+				responseBytes[1] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+			}
+
+			AddCrc(responseBytes);
+			return [.. responseBytes];
+		}
+
+		private async Task<byte[]> HandleEncapsulatedInterfaceAsync(byte[] requestBytes, CancellationToken cancellationToken)
+		{
+			var responseBytes = new List<byte>();
+			responseBytes.AddRange(requestBytes.Take(2));
+
+			if (requestBytes[2] != 0x0E)
+			{
+				responseBytes[1] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.IllegalFunction);
+
+				AddCrc(responseBytes);
+				return [.. responseBytes];
+			}
+
+			var firstObject = (ModbusDeviceIdentificationObject)requestBytes[4];
+			if (0x06 < requestBytes[4] && requestBytes[4] < 0x80)
+			{
+				responseBytes[1] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.IllegalDataAddress);
+
+				AddCrc(responseBytes);
+				return [.. responseBytes];
+			}
+
+			var category = (ModbusDeviceIdentificationCategory)requestBytes[3];
+			if (!Enum.IsDefined(typeof(ModbusDeviceIdentificationCategory), category))
+			{
+				responseBytes[1] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.IllegalDataValue);
+
+				AddCrc(responseBytes);
+				return [.. responseBytes];
+			}
+
+			try
+			{
+				var res = await Client.ReadDeviceIdentificationAsync(requestBytes[6], category, firstObject, cancellationToken);
+
+				var bodyBytes = new List<byte>();
+
+				// MEI, Category
+				bodyBytes.AddRange(requestBytes.Skip(2).Take(2));
+
+				// Conformity
+				bodyBytes.Add((byte)category);
+				if (res.IsIndividualAccessAllowed)
+					bodyBytes[2] |= 0x80;
+
+				// More, NextId, NumberOfObjects
+				bodyBytes.AddRange(new byte[3]);
+
+				int maxObjectId;
+				switch (category)
+				{
+					case ModbusDeviceIdentificationCategory.Basic:
+						maxObjectId = 0x02;
+						break;
+
+					case ModbusDeviceIdentificationCategory.Regular:
+						maxObjectId = 0x06;
+						break;
+
+					case ModbusDeviceIdentificationCategory.Extended:
+						maxObjectId = 0xFF;
+						break;
+
+					default: // Individual
+						maxObjectId = requestBytes[4];
+						break;
+				}
+
+				byte numberOfObjects = 0;
+				for (int i = requestBytes[4]; i <= maxObjectId; i++)
+				{
+					// Reserved
+					if (0x07 <= i && i <= 0x7F)
+						continue;
+
+					byte[] objBytes = GetDeviceObject((byte)i, res);
+
+					// We need to split the response if it would exceed the max ADU size
+					if (responseBytes.Count + bodyBytes.Count + objBytes.Length > RtuProtocol.MAX_ADU_LENGTH)
+					{
+						bodyBytes[3] = 0xFF;
+						bodyBytes[4] = (byte)i;
+
+						bodyBytes[5] = numberOfObjects;
+						responseBytes.AddRange(bodyBytes);
+						return [.. responseBytes];
+					}
+
+					bodyBytes.AddRange(objBytes);
+					numberOfObjects++;
+				}
+
+				bodyBytes[5] = numberOfObjects;
+				responseBytes.AddRange(bodyBytes);
+
+				AddCrc(responseBytes);
+				return [.. responseBytes];
+			}
+			catch
+			{
+				responseBytes[1] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+
+				AddCrc(responseBytes);
+				return [.. responseBytes];
+			}
+		}
+
+		private byte[] GetDeviceObject(byte objectId, DeviceIdentification deviceIdentification)
+		{
+			var result = new List<byte> { objectId };
+			switch ((ModbusDeviceIdentificationObject)objectId)
+			{
+				case ModbusDeviceIdentificationObject.VendorName:
+					{
+						byte[] bytes = Encoding.UTF8.GetBytes(deviceIdentification.VendorName);
+						result.Add((byte)bytes.Length);
+						result.AddRange(bytes);
+					}
+					break;
+
+				case ModbusDeviceIdentificationObject.ProductCode:
+					{
+						byte[] bytes = Encoding.UTF8.GetBytes(deviceIdentification.ProductCode);
+						result.Add((byte)bytes.Length);
+						result.AddRange(bytes);
+					}
+					break;
+
+				case ModbusDeviceIdentificationObject.MajorMinorRevision:
+					{
+						byte[] bytes = Encoding.UTF8.GetBytes(deviceIdentification.MajorMinorRevision);
+						result.Add((byte)bytes.Length);
+						result.AddRange(bytes);
+					}
+					break;
+
+				case ModbusDeviceIdentificationObject.VendorUrl:
+					{
+						byte[] bytes = Encoding.UTF8.GetBytes(deviceIdentification.VendorUrl);
+						result.Add((byte)bytes.Length);
+						result.AddRange(bytes);
+					}
+					break;
+
+				case ModbusDeviceIdentificationObject.ProductName:
+					{
+						byte[] bytes = Encoding.UTF8.GetBytes(deviceIdentification.ProductName);
+						result.Add((byte)bytes.Length);
+						result.AddRange(bytes);
+					}
+					break;
+
+				case ModbusDeviceIdentificationObject.ModelName:
+					{
+						byte[] bytes = Encoding.UTF8.GetBytes(deviceIdentification.ModelName);
+						result.Add((byte)bytes.Length);
+						result.AddRange(bytes);
+					}
+					break;
+
+				case ModbusDeviceIdentificationObject.UserApplicationName:
+					{
+						byte[] bytes = Encoding.UTF8.GetBytes(deviceIdentification.UserApplicationName);
+						result.Add((byte)bytes.Length);
+						result.AddRange(bytes);
+					}
+					break;
+
+				default:
+					{
+						if (deviceIdentification.ExtendedObjects.ContainsKey(objectId))
+						{
+							byte[] bytes = deviceIdentification.ExtendedObjects[objectId];
+							result.Add((byte)bytes.Length);
+							result.AddRange(bytes);
+						}
+						else
+						{
+							result.Add(0x00);
+						}
+					}
+					break;
+			}
+
+			return [.. result];
+		}
+
+		private static void SetCrc(byte[] bytes)
+		{
+			byte[] crc = RtuProtocol.CRC16(bytes, 0, bytes.Length - 2);
+			bytes[bytes.Length - 2] = crc[0];
+			bytes[bytes.Length - 1] = crc[1];
+		}
+
+		private static void AddCrc(List<byte> bytes)
+		{
+			byte[] crc = RtuProtocol.CRC16(bytes);
+			bytes.Add(crc[0]);
+			bytes.Add(crc[1]);
+		}
+
+		#endregion Request Handling
+	}
+}

AMWD.Protocols.Modbus.Proxy/ModbusTcpProxy.cs

@@ -0,0 +1,855 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Net;
+using System.Net.Sockets;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+using AMWD.Protocols.Modbus.Common;
+using AMWD.Protocols.Modbus.Common.Contracts;
+using AMWD.Protocols.Modbus.Common.Protocols;
+
+namespace AMWD.Protocols.Modbus.Proxy
+{
+	/// <summary>
+	/// Implements a Modbus TCP server proxying all requests to a Modbus client of choice.
+	/// </summary>
+	public class ModbusTcpProxy : IDisposable
+	{
+		#region Fields
+
+		private bool _isDisposed;
+
+		private TcpListener _listener;
+		private CancellationTokenSource _stopCts;
+		private Task _clientConnectTask = Task.CompletedTask;
+
+		private readonly SemaphoreSlim _clientListLock = new(1, 1);
+		private readonly List<TcpClient> _clients = [];
+		private readonly List<Task> _clientTasks = [];
+
+		#endregion Fields
+
+		#region Constructors
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="ModbusTcpProxy"/> class.
+		/// </summary>
+		/// <param name="client">The <see cref="ModbusClientBase"/> used to request the remote device, that should be proxied.</param>
+		/// <param name="listenAddress">An <see cref="IPAddress"/> to listen on (Default: <see cref="IPAddress.Loopback"/>).</param>
+		/// <param name="listenPort">A port to listen on (Default: 502).</param>
+		public ModbusTcpProxy(ModbusClientBase client, IPAddress listenAddress = null, int listenPort = 502)
+		{
+			Client = client ?? throw new ArgumentNullException(nameof(client));
+
+			ListenAddress = listenAddress ?? IPAddress.Loopback;
+
+			if (ushort.MinValue < listenPort || listenPort < ushort.MaxValue)
+				throw new ArgumentOutOfRangeException(nameof(listenPort));
+
+			try
+			{
+#if NET8_0_OR_GREATER
+				using var testListener = new TcpListener(ListenAddress, listenPort);
+#else
+				var testListener = new TcpListener(ListenAddress, listenPort);
+#endif
+				testListener.Start(1);
+				ListenPort = (testListener.LocalEndpoint as IPEndPoint).Port;
+				testListener.Stop();
+			}
+			catch (Exception ex)
+			{
+				throw new ArgumentException($"{nameof(ListenPort)} ({listenPort}) is already in use.", ex);
+			}
+		}
+
+		#endregion Constructors
+
+		#region Properties
+
+		/// <summary>
+		/// Gets the Modbus client used to request the remote device, that should be proxied.
+		/// </summary>
+		public ModbusClientBase Client { get; }
+
+		/// <summary>
+		/// Gets the <see cref="IPAddress"/> to listen on.
+		/// </summary>
+		public IPAddress ListenAddress { get; }
+
+		/// <summary>
+		/// Get the port to listen on.
+		/// </summary>
+		public int ListenPort { get; }
+
+		/// <summary>
+		/// Gets a value indicating whether the server is running.
+		/// </summary>
+		public bool IsRunning => _listener?.Server.IsBound ?? false;
+
+		/// <summary>
+		/// Gets or sets the read/write timeout for the incoming connections (not the <see cref="Client"/>!).
+		/// </summary>
+		public TimeSpan ReadWriteTimeout { get; set; }
+
+		#endregion Properties
+
+		#region Control Methods
+
+		/// <summary>
+		/// Starts the server.
+		/// </summary>
+		/// <param name="cancellationToken">A cancellation token used to propagate notification that this operation should be canceled.</param>
+		public Task StartAsync(CancellationToken cancellationToken = default)
+		{
+			Assertions();
+
+			_stopCts?.Cancel();
+
+			_listener?.Stop();
+#if NET8_0_OR_GREATER
+			_listener?.Dispose();
+#endif
+
+			_stopCts?.Dispose();
+			_stopCts = new CancellationTokenSource();
+
+			_listener = new TcpListener(ListenAddress, ListenPort);
+			if (ListenAddress.AddressFamily == AddressFamily.InterNetworkV6)
+				_listener.Server.DualMode = true;
+
+			_listener.Start();
+			_clientConnectTask = WaitForClientAsync(_stopCts.Token);
+
+			return Task.CompletedTask;
+		}
+
+		/// <summary>
+		/// Stops the server.
+		/// </summary>
+		/// <param name="cancellationToken">A cancellation token used to propagate notification that this operation should be canceled.</param>
+		public Task StopAsync(CancellationToken cancellationToken = default)
+		{
+			Assertions();
+			return StopAsyncInternal(cancellationToken);
+		}
+
+		private async Task StopAsyncInternal(CancellationToken cancellationToken = default)
+		{
+			_stopCts.Cancel();
+
+			_listener.Stop();
+#if NET8_0_OR_GREATER
+			_listener.Dispose();
+#endif
+			try
+			{
+				await Task.WhenAny(_clientConnectTask, Task.Delay(Timeout.Infinite, cancellationToken));
+			}
+			catch (OperationCanceledException)
+			{
+				// Terminated
+			}
+
+			try
+			{
+				await Task.WhenAny(Task.WhenAll(_clientTasks), Task.Delay(Timeout.Infinite, cancellationToken));
+			}
+			catch (OperationCanceledException)
+			{
+				// Terminated
+			}
+		}
+
+		/// <summary>
+		/// Releases all managed and unmanaged resources used by the <see cref="ModbusTcpProxy"/>.
+		/// </summary>
+		public void Dispose()
+		{
+			if (_isDisposed)
+				return;
+
+			_isDisposed = true;
+
+			StopAsyncInternal(CancellationToken.None).Wait();
+
+			_clientListLock.Dispose();
+			_clients.Clear();
+
+			_stopCts?.Dispose();
+		}
+
+		private void Assertions()
+		{
+#if NET8_0_OR_GREATER
+			ObjectDisposedException.ThrowIf(_isDisposed, this);
+#else
+			if (_isDisposed)
+				throw new ObjectDisposedException(GetType().FullName);
+#endif
+		}
+
+		#endregion Control Methods
+
+		#region Client Handling
+
+		private async Task WaitForClientAsync(CancellationToken cancellationToken)
+		{
+			while (!cancellationToken.IsCancellationRequested)
+			{
+				try
+				{
+#if NET8_0_OR_GREATER
+					var client = await _listener.AcceptTcpClientAsync(cancellationToken);
+#else
+					var client = await _listener.AcceptTcpClientAsync();
+#endif
+					await _clientListLock.WaitAsync(cancellationToken);
+					try
+					{
+						_clients.Add(client);
+						_clientTasks.Add(HandleClientAsync(client, cancellationToken));
+					}
+					finally
+					{
+						_clientListLock.Release();
+					}
+				}
+				catch
+				{
+					// There might be a failure here, that's ok, just keep it quiet
+				}
+			}
+		}
+
+		private async Task HandleClientAsync(TcpClient client, CancellationToken cancellationToken)
+		{
+			try
+			{
+				var stream = client.GetStream();
+				while (!cancellationToken.IsCancellationRequested)
+				{
+					var requestBytes = new List<byte>();
+
+					using (var cts = new CancellationTokenSource(ReadWriteTimeout))
+					using (cancellationToken.Register(cts.Cancel))
+					{
+						byte[] headerBytes = await stream.ReadExpectedBytesAsync(6, cts.Token);
+						requestBytes.AddRange(headerBytes);
+
+						byte[] followingCountBytes = headerBytes.Skip(4).Take(2).ToArray();
+						followingCountBytes.SwapBigEndian();
+						int followingCount = BitConverter.ToUInt16(followingCountBytes, 0);
+
+						byte[] bodyBytes = await stream.ReadExpectedBytesAsync(followingCount, cts.Token);
+						requestBytes.AddRange(bodyBytes);
+					}
+
+					byte[] responseBytes = await HandleRequestAsync([.. requestBytes], cancellationToken);
+					if (responseBytes != null)
+						await stream.WriteAsync(responseBytes, 0, responseBytes.Length, cancellationToken);
+				}
+			}
+			catch
+			{
+				// Keep client processing quiet
+			}
+			finally
+			{
+				await _clientListLock.WaitAsync(cancellationToken);
+				try
+				{
+					_clients.Remove(client);
+					client.Dispose();
+				}
+				finally
+				{
+					_clientListLock.Release();
+				}
+			}
+		}
+
+		#endregion Client Handling
+
+		#region Request Handling
+
+		private Task<byte[]> HandleRequestAsync(byte[] requestBytes, CancellationToken cancellationToken)
+		{
+			switch ((ModbusFunctionCode)requestBytes[7])
+			{
+				case ModbusFunctionCode.ReadCoils:
+					return HandleReadCoilsAsync(requestBytes, cancellationToken);
+
+				case ModbusFunctionCode.ReadDiscreteInputs:
+					return HandleReadDiscreteInputsAsync(requestBytes, cancellationToken);
+
+				case ModbusFunctionCode.ReadHoldingRegisters:
+					return HandleReadHoldingRegistersAsync(requestBytes, cancellationToken);
+
+				case ModbusFunctionCode.ReadInputRegisters:
+					return HandleReadInputRegistersAsync(requestBytes, cancellationToken);
+
+				case ModbusFunctionCode.WriteSingleCoil:
+					return HandleWriteSingleCoilAsync(requestBytes, cancellationToken);
+
+				case ModbusFunctionCode.WriteSingleRegister:
+					return HandleWriteSingleRegisterAsync(requestBytes, cancellationToken);
+
+				case ModbusFunctionCode.WriteMultipleCoils:
+					return HandleWriteMultipleCoilsAsync(requestBytes, cancellationToken);
+
+				case ModbusFunctionCode.WriteMultipleRegisters:
+					return HandleWriteMultipleRegistersAsync(requestBytes, cancellationToken);
+
+				case ModbusFunctionCode.EncapsulatedInterface:
+					return HandleEncapsulatedInterfaceAsync(requestBytes, cancellationToken);
+
+				default: // unknown function
+					{
+						byte[] responseBytes = new byte[9];
+						Array.Copy(requestBytes, 0, responseBytes, 0, 8);
+
+						// Mark as error
+						responseBytes[7] |= 0x80;
+
+						responseBytes[8] = (byte)ModbusErrorCode.IllegalFunction;
+						return Task.FromResult(responseBytes);
+					}
+			}
+		}
+
+		private async Task<byte[]> HandleReadCoilsAsync(byte[] requestBytes, CancellationToken cancellationToken)
+		{
+			if (requestBytes.Length < 12)
+				return null;
+
+			byte unitId = requestBytes[6];
+			ushort firstAddress = requestBytes.GetBigEndianUInt16(8);
+			ushort count = requestBytes.GetBigEndianUInt16(10);
+
+			var responseBytes = new List<byte>();
+			responseBytes.AddRange(requestBytes.Take(8));
+			try
+			{
+				var coils = await Client.ReadCoilsAsync(unitId, firstAddress, count, cancellationToken);
+
+				byte[] values = new byte[(int)Math.Ceiling(coils.Count / 8.0)];
+				for (int i = 0; i < coils.Count; i++)
+				{
+					if (coils[i].Value)
+					{
+						int byteIndex = i / 8;
+						int bitIndex = i % 8;
+
+						values[byteIndex] |= (byte)(1 << bitIndex);
+					}
+				}
+
+				responseBytes.Add((byte)values.Length);
+				responseBytes.AddRange(values);
+			}
+			catch
+			{
+				responseBytes[7] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+			}
+
+			return [.. responseBytes];
+		}
+
+		private async Task<byte[]> HandleReadDiscreteInputsAsync(byte[] requestBytes, CancellationToken cancellationToken)
+		{
+			if (requestBytes.Length < 12)
+				return null;
+
+			byte unitId = requestBytes[6];
+			ushort firstAddress = requestBytes.GetBigEndianUInt16(8);
+			ushort count = requestBytes.GetBigEndianUInt16(10);
+
+			var responseBytes = new List<byte>();
+			responseBytes.AddRange(requestBytes.Take(8));
+			try
+			{
+				var discreteInputs = await Client.ReadDiscreteInputsAsync(unitId, firstAddress, count, cancellationToken);
+
+				byte[] values = new byte[(int)Math.Ceiling(discreteInputs.Count / 8.0)];
+				for (int i = 0; i < discreteInputs.Count; i++)
+				{
+					if (discreteInputs[i].Value)
+					{
+						int byteIndex = i / 8;
+						int bitIndex = i % 8;
+
+						values[byteIndex] |= (byte)(1 << bitIndex);
+					}
+				}
+
+				responseBytes.Add((byte)values.Length);
+				responseBytes.AddRange(values);
+			}
+			catch
+			{
+				responseBytes[7] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+			}
+
+			return [.. responseBytes];
+		}
+
+		private async Task<byte[]> HandleReadHoldingRegistersAsync(byte[] requestBytes, CancellationToken cancellationToken)
+		{
+			if (requestBytes.Length < 12)
+				return null;
+
+			byte unitId = requestBytes[6];
+			ushort firstAddress = requestBytes.GetBigEndianUInt16(8);
+			ushort count = requestBytes.GetBigEndianUInt16(10);
+
+			var responseBytes = new List<byte>();
+			responseBytes.AddRange(requestBytes.Take(8));
+			try
+			{
+				var holdingRegisters = await Client.ReadHoldingRegistersAsync(unitId, firstAddress, count, cancellationToken);
+
+				byte[] values = new byte[holdingRegisters.Count * 2];
+				for (int i = 0; i < holdingRegisters.Count; i++)
+				{
+					values[i * 2] = holdingRegisters[i].HighByte;
+					values[i * 2 + 1] = holdingRegisters[i].LowByte;
+				}
+
+				responseBytes.Add((byte)values.Length);
+				responseBytes.AddRange(values);
+			}
+			catch
+			{
+				responseBytes[7] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+			}
+
+			return [.. responseBytes];
+		}
+
+		private async Task<byte[]> HandleReadInputRegistersAsync(byte[] requestBytes, CancellationToken cancellationToken)
+		{
+			if (requestBytes.Length < 12)
+				return null;
+
+			byte unitId = requestBytes[6];
+			ushort firstAddress = requestBytes.GetBigEndianUInt16(8);
+			ushort count = requestBytes.GetBigEndianUInt16(10);
+
+			var responseBytes = new List<byte>();
+			responseBytes.AddRange(requestBytes.Take(8));
+			try
+			{
+				var inputRegisters = await Client.ReadInputRegistersAsync(unitId, firstAddress, count, cancellationToken);
+
+				byte[] values = new byte[count * 2];
+				for (int i = 0; i < count; i++)
+				{
+					values[i * 2] = inputRegisters[i].HighByte;
+					values[i * 2 + 1] = inputRegisters[i].LowByte;
+				}
+
+				responseBytes.Add((byte)values.Length);
+				responseBytes.AddRange(values);
+			}
+			catch
+			{
+				responseBytes[7] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+			}
+
+			return [.. responseBytes];
+		}
+
+		private async Task<byte[]> HandleWriteSingleCoilAsync(byte[] requestBytes, CancellationToken cancellationToken)
+		{
+			if (requestBytes.Length < 12)
+				return null;
+
+			var responseBytes = new List<byte>();
+			responseBytes.AddRange(requestBytes.Take(8));
+
+			ushort address = requestBytes.GetBigEndianUInt16(8);
+
+			if (requestBytes[10] != 0x00 && requestBytes[10] != 0xFF)
+			{
+				responseBytes[7] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.IllegalDataValue);
+				return [.. responseBytes];
+			}
+
+			try
+			{
+				var coil = new Coil
+				{
+					Address = address,
+					HighByte = requestBytes[10],
+					LowByte = requestBytes[11],
+				};
+
+				bool isSuccess = await Client.WriteSingleCoilAsync(requestBytes[6], coil, cancellationToken);
+				if (isSuccess)
+				{
+					// Response is an echo of the request
+					responseBytes.AddRange(requestBytes.Skip(8).Take(4));
+				}
+				else
+				{
+					responseBytes[7] |= 0x80;
+					responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+				}
+			}
+			catch
+			{
+				responseBytes[7] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+			}
+
+			return [.. responseBytes];
+		}
+
+		private async Task<byte[]> HandleWriteSingleRegisterAsync(byte[] requestBytes, CancellationToken cancellationToken)
+		{
+			if (requestBytes.Length < 12)
+				return null;
+
+			var responseBytes = new List<byte>();
+			responseBytes.AddRange(requestBytes.Take(8));
+
+			ushort address = requestBytes.GetBigEndianUInt16(8);
+
+			try
+			{
+				var register = new HoldingRegister
+				{
+					Address = address,
+					HighByte = requestBytes[10],
+					LowByte = requestBytes[11]
+				};
+
+				bool isSuccess = await Client.WriteSingleHoldingRegisterAsync(requestBytes[6], register, cancellationToken);
+				if (isSuccess)
+				{
+					// Response is an echo of the request
+					responseBytes.AddRange(requestBytes.Skip(8).Take(4));
+				}
+				else
+				{
+					responseBytes[7] |= 0x80;
+					responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+				}
+			}
+			catch
+			{
+				responseBytes[7] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+			}
+
+			return [.. responseBytes];
+		}
+
+		private async Task<byte[]> HandleWriteMultipleCoilsAsync(byte[] requestBytes, CancellationToken cancellationToken)
+		{
+			if (requestBytes.Length < 13)
+				return null;
+
+			var responseBytes = new List<byte>();
+			responseBytes.AddRange(requestBytes.Take(8));
+
+			ushort firstAddress = requestBytes.GetBigEndianUInt16(8);
+			ushort count = requestBytes.GetBigEndianUInt16(10);
+
+			int byteCount = (int)Math.Ceiling(count / 8.0);
+			if (requestBytes.Length < 13 + byteCount)
+			{
+				responseBytes[7] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.IllegalDataValue);
+				return [.. responseBytes];
+			}
+
+			try
+			{
+				int baseOffset = 13;
+				var coils = new List<Coil>();
+				for (int i = 0; i < count; i++)
+				{
+					int bytePosition = i / 8;
+					int bitPosition = i % 8;
+
+					ushort address = (ushort)(firstAddress + i);
+					bool value = (requestBytes[baseOffset + bytePosition] & (1 << bitPosition)) > 0;
+
+					coils.Add(new Coil
+					{
+						Address = address,
+						HighByte = value ? (byte)0xFF : (byte)0x00
+					});
+				}
+
+				bool isSuccess = await Client.WriteMultipleCoilsAsync(requestBytes[6], coils, cancellationToken);
+				if (isSuccess)
+				{
+					// Response is an echo of the request
+					responseBytes.AddRange(requestBytes.Skip(8).Take(4));
+				}
+				else
+				{
+					responseBytes[7] |= 0x80;
+					responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+				}
+			}
+			catch
+			{
+				responseBytes[7] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+			}
+
+			return [.. responseBytes];
+		}
+
+		private async Task<byte[]> HandleWriteMultipleRegistersAsync(byte[] requestBytes, CancellationToken cancellationToken)
+		{
+			if (requestBytes.Length < 13)
+				return null;
+
+			var responseBytes = new List<byte>();
+			responseBytes.AddRange(requestBytes.Take(8));
+
+			ushort firstAddress = requestBytes.GetBigEndianUInt16(8);
+			ushort count = requestBytes.GetBigEndianUInt16(10);
+
+			int byteCount = count * 2;
+			if (requestBytes.Length < 13 + byteCount)
+			{
+				responseBytes[7] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.IllegalDataValue);
+				return [.. responseBytes];
+			}
+
+			try
+			{
+				int baseOffset = 13;
+				var list = new List<HoldingRegister>();
+				for (int i = 0; i < count; i++)
+				{
+					ushort address = (ushort)(firstAddress + i);
+
+					list.Add(new HoldingRegister
+					{
+						Address = address,
+						HighByte = requestBytes[baseOffset + i * 2],
+						LowByte = requestBytes[baseOffset + i * 2 + 1]
+					});
+
+					bool isSuccess = await Client.WriteMultipleHoldingRegistersAsync(requestBytes[6], list, cancellationToken);
+					if (isSuccess)
+					{
+						// Response is an echo of the request
+						responseBytes.AddRange(requestBytes.Skip(8).Take(4));
+					}
+					else
+					{
+						responseBytes[7] |= 0x80;
+						responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+					}
+				}
+			}
+			catch
+			{
+				responseBytes[7] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+			}
+
+			return [.. responseBytes];
+		}
+
+		private async Task<byte[]> HandleEncapsulatedInterfaceAsync(byte[] requestBytes, CancellationToken cancellationToken)
+		{
+			var responseBytes = new List<byte>();
+			responseBytes.AddRange(requestBytes.Take(8));
+
+			if (requestBytes[8] != 0x0E)
+			{
+				responseBytes[7] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.IllegalFunction);
+				return [.. responseBytes];
+			}
+
+			var firstObject = (ModbusDeviceIdentificationObject)requestBytes[10];
+			if (0x06 < requestBytes[10] && requestBytes[10] < 0x80)
+			{
+				responseBytes[7] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.IllegalDataAddress);
+				return [.. responseBytes];
+			}
+
+			var category = (ModbusDeviceIdentificationCategory)requestBytes[9];
+			if (!Enum.IsDefined(typeof(ModbusDeviceIdentificationCategory), category))
+			{
+				responseBytes[7] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.IllegalDataValue);
+				return [.. responseBytes];
+			}
+
+			try
+			{
+				var res = await Client.ReadDeviceIdentificationAsync(requestBytes[6], category, firstObject, cancellationToken);
+
+				var bodyBytes = new List<byte>();
+
+				// MEI, Category
+				bodyBytes.AddRange(requestBytes.Skip(8).Take(2));
+
+				// Conformity
+				bodyBytes.Add((byte)category);
+				if (res.IsIndividualAccessAllowed)
+					bodyBytes[2] |= 0x80;
+
+				// More, NextId, NumberOfObjects
+				bodyBytes.AddRange(new byte[3]);
+
+				int maxObjectId;
+				switch (category)
+				{
+					case ModbusDeviceIdentificationCategory.Basic:
+						maxObjectId = 0x02;
+						break;
+
+					case ModbusDeviceIdentificationCategory.Regular:
+						maxObjectId = 0x06;
+						break;
+
+					case ModbusDeviceIdentificationCategory.Extended:
+						maxObjectId = 0xFF;
+						break;
+
+					default: // Individual
+						maxObjectId = requestBytes[10];
+						break;
+				}
+
+				byte numberOfObjects = 0;
+				for (int i = requestBytes[10]; i <= maxObjectId; i++)
+				{
+					// Reserved
+					if (0x07 <= i && i <= 0x7F)
+						continue;
+
+					byte[] objBytes = GetDeviceObject((byte)i, res);
+
+					// We need to split the response if it would exceed the max ADU size
+					if (responseBytes.Count + bodyBytes.Count + objBytes.Length > TcpProtocol.MAX_ADU_LENGTH)
+					{
+						bodyBytes[3] = 0xFF;
+						bodyBytes[4] = (byte)i;
+
+						bodyBytes[5] = numberOfObjects;
+						responseBytes.AddRange(bodyBytes);
+						return [.. responseBytes];
+					}
+
+					bodyBytes.AddRange(objBytes);
+					numberOfObjects++;
+				}
+
+				bodyBytes[5] = numberOfObjects;
+				responseBytes.AddRange(bodyBytes);
+				return [.. responseBytes];
+			}
+			catch
+			{
+				responseBytes[7] |= 0x80;
+				responseBytes.Add((byte)ModbusErrorCode.SlaveDeviceFailure);
+				return [.. responseBytes];
+			}
+		}
+
+		private byte[] GetDeviceObject(byte objectId, DeviceIdentification deviceIdentification)
+		{
+			var result = new List<byte> { objectId };
+			switch ((ModbusDeviceIdentificationObject)objectId)
+			{
+				case ModbusDeviceIdentificationObject.VendorName:
+					{
+						byte[] bytes = Encoding.UTF8.GetBytes(deviceIdentification.VendorName);
+						result.Add((byte)bytes.Length);
+						result.AddRange(bytes);
+					}
+					break;
+
+				case ModbusDeviceIdentificationObject.ProductCode:
+					{
+						byte[] bytes = Encoding.UTF8.GetBytes(deviceIdentification.ProductCode);
+						result.Add((byte)bytes.Length);
+						result.AddRange(bytes);
+					}
+					break;
+
+				case ModbusDeviceIdentificationObject.MajorMinorRevision:
+					{
+						byte[] bytes = Encoding.UTF8.GetBytes(deviceIdentification.MajorMinorRevision);
+						result.Add((byte)bytes.Length);
+						result.AddRange(bytes);
+					}
+					break;
+
+				case ModbusDeviceIdentificationObject.VendorUrl:
+					{
+						byte[] bytes = Encoding.UTF8.GetBytes(deviceIdentification.VendorUrl);
+						result.Add((byte)bytes.Length);
+						result.AddRange(bytes);
+					}
+					break;
+
+				case ModbusDeviceIdentificationObject.ProductName:
+					{
+						byte[] bytes = Encoding.UTF8.GetBytes(deviceIdentification.ProductName);
+						result.Add((byte)bytes.Length);
+						result.AddRange(bytes);
+					}
+					break;
+
+				case ModbusDeviceIdentificationObject.ModelName:
+					{
+						byte[] bytes = Encoding.UTF8.GetBytes(deviceIdentification.ModelName);
+						result.Add((byte)bytes.Length);
+						result.AddRange(bytes);
+					}
+					break;
+
+				case ModbusDeviceIdentificationObject.UserApplicationName:
+					{
+						byte[] bytes = Encoding.UTF8.GetBytes(deviceIdentification.UserApplicationName);
+						result.Add((byte)bytes.Length);
+						result.AddRange(bytes);
+					}
+					break;
+
+				default:
+					{
+						if (deviceIdentification.ExtendedObjects.ContainsKey(objectId))
+						{
+							byte[] bytes = deviceIdentification.ExtendedObjects[objectId];
+							result.Add((byte)bytes.Length);
+							result.AddRange(bytes);
+						}
+						else
+						{
+							result.Add(0x00);
+						}
+					}
+					break;
+			}
+
+			return [.. result];
+		}
+
+		#endregion Request Handling
+	}
+}

AMWD.Protocols.Modbus.Proxy/README.md

@@ -0,0 +1,10 @@
+# Modbus Protocol for .NET | Proxy
+
+With this package the server and client implementations will be combined as proxy.
+
+You can use any `ModbusBasClient` implementation as target client and plug it into the implemented `ModbusTcpProxy` or `ModbusRtuProxy`, which implement the server side.
+
+
+---
+
+Published under MIT License (see [**tl;dr**Legal](https://www.tldrlegal.com/license/mit-license))

AMWD.Protocols.Modbus.Serial/ModbusRtuServer.cs

@@ -14,10 +14,10 @@ using AMWD.Protocols.Modbus.Common.Protocols;
 namespace AMWD.Protocols.Modbus.Serial
 {
 	/// <summary>
-	/// A basic implementation of a Modbus serial line server.
+	/// A basic implementation of a Modbus serial line RTU server.
 	/// </summary>
 	[System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
-	public class ModbusSerialServer : IDisposable
+	public class ModbusRtuServer : IDisposable
 	{
 		#region Fields
 
@@ -34,11 +34,11 @@ namespace AMWD.Protocols.Modbus.Serial
 		#region Constructors
 
 		/// <summary>
-		/// Initializes a new instance of the <see cref="ModbusSerialServer"/> class.
+		/// Initializes a new instance of the <see cref="ModbusRtuServer"/> class.
 		/// </summary>
 		/// <param name="portName">The name of the serial port to use.</param>
 		/// <param name="baudRate">The baud rate of the serial port (Default: 19.200).</param>
-		public ModbusSerialServer(string portName, BaudRate baudRate = BaudRate.Baud19200)
+		public ModbusRtuServer(string portName, BaudRate baudRate = BaudRate.Baud19200)
 		{
 			if (string.IsNullOrWhiteSpace(portName))
 				throw new ArgumentNullException(nameof(portName));
@@ -195,7 +195,7 @@ namespace AMWD.Protocols.Modbus.Serial
 		}
 
 		/// <summary>
-		/// Releases all managed and unmanaged resources used by the <see cref="ModbusSerialServer"/>.
+		/// Releases all managed and unmanaged resources used by the <see cref="ModbusRtuServer"/>.
 		/// </summary>
 		public void Dispose()
 		{
@@ -208,6 +208,9 @@ namespace AMWD.Protocols.Modbus.Serial
 
 			_deviceListLock.Dispose();
 			_devices.Clear();
+
+			_serialPort.Dispose();
+			_stopCts?.Dispose();
 		}
 
 		private void Assertions()

AMWD.Protocols.Modbus.Serial/ModbusSerialClient.cs

@@ -43,9 +43,6 @@ namespace AMWD.Protocols.Modbus.Serial
 		/// <inheritdoc cref="SerialPort.GetPortNames" />
 		public static string[] AvailablePortNames => SerialPort.GetPortNames();
 
-		/// <inheritdoc/>
-		public override IModbusProtocol Protocol { get; set; }
-
 		/// <inheritdoc cref="IModbusConnection.IdleTimeout"/>
 		public TimeSpan IdleTimeout
 		{

AMWD.Protocols.Modbus.Serial/ModbusSerialConnection.cs

@@ -259,7 +259,7 @@ namespace AMWD.Protocols.Modbus.Serial
 				try
 				{
 					// Get next request to process
-					var item = await _requestQueue.DequeueAsync(cancellationToken).ConfigureAwait(false);
+					var item = await _requestQueue.DequeueAsync(cancellationToken);
 
 					// Remove registration => already removed from queue
 					item.CancellationTokenRegistration.Dispose();
@@ -267,13 +267,13 @@ namespace AMWD.Protocols.Modbus.Serial
 					// Build combined cancellation token
 					using var linkedCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken, item.CancellationTokenSource.Token);
 					// Wait for exclusive access
-					await _portLock.WaitAsync(linkedCts.Token).ConfigureAwait(false);
+					await _portLock.WaitAsync(linkedCts.Token);
 					try
 					{
 						// Ensure connection is up
-						await AssertConnection(linkedCts.Token).ConfigureAwait(false);
+						await AssertConnection(linkedCts.Token);
 
-						await _serialPort.WriteAsync(item.Request, linkedCts.Token).ConfigureAwait(false);
+						await _serialPort.WriteAsync(item.Request, linkedCts.Token);
 
 						linkedCts.Token.ThrowIfCancellationRequested();
 
@@ -282,7 +282,7 @@ namespace AMWD.Protocols.Modbus.Serial
 
 						do
 						{
-							int readCount = await _serialPort.ReadAsync(buffer, 0, buffer.Length, linkedCts.Token).ConfigureAwait(false);
+							int readCount = await _serialPort.ReadAsync(buffer, 0, buffer.Length, linkedCts.Token);
 							if (readCount < 1)
 								throw new EndOfStreamException();
 
@@ -313,7 +313,7 @@ namespace AMWD.Protocols.Modbus.Serial
 						_portLock.Release();
 						_idleTimer.Change(IdleTimeout, Timeout.InfiniteTimeSpan);
 
-						await Task.Delay(InterRequestDelay, cancellationToken).ConfigureAwait(false);
+						await Task.Delay(InterRequestDelay, cancellationToken);
 					}
 				}
 				catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested)
@@ -370,7 +370,7 @@ namespace AMWD.Protocols.Modbus.Serial
 
 					try
 					{
-						await Task.Delay(TimeSpan.FromSeconds(delay), cancellationToken).ConfigureAwait(false);
+						await Task.Delay(TimeSpan.FromSeconds(delay), cancellationToken);
 					}
 					catch
 					{ /* keep it quiet */ }

AMWD.Protocols.Modbus.Serial/README.md

@@ -22,6 +22,19 @@ float voltage = registers.GetSingle();
 Console.WriteLine($"The voltage of device #{unitId} between L1 and N is: {voltage:N2}V");
 ```
 
+If you want to use the `ASCII` protocol instead, you can do this on initialization:
+
+```csharp
+// [...]
+
+using var client = new ModbusSerialClient(serialPort)
+{
+	Protocol = new AsciiProtocol();
+};
+
+// [...]
+```
+
 
 ## Sources
 

AMWD.Protocols.Modbus.Serial/Utils/SerialPortWrapper.cs

@@ -145,7 +145,7 @@ namespace AMWD.Protocols.Modbus.Serial.Utils
 
 			try
 			{
-				return await _serialPort.BaseStream.ReadAsync(buffer, offset, count, cts.Token).ConfigureAwait(false);
+				return await _serialPort.BaseStream.ReadAsync(buffer, offset, count, cts.Token);
 			}
 			catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested)
 			{
@@ -195,9 +195,9 @@ namespace AMWD.Protocols.Modbus.Serial.Utils
 			try
 			{
 #if NET6_0_OR_GREATER
-				await _serialPort.BaseStream.WriteAsync(buffer, cts.Token).ConfigureAwait(false);
+				await _serialPort.BaseStream.WriteAsync(buffer, cts.Token);
 #else
-				await _serialPort.BaseStream.WriteAsync(buffer, 0, buffer.Length, cts.Token).ConfigureAwait(false);
+				await _serialPort.BaseStream.WriteAsync(buffer, 0, buffer.Length, cts.Token);
 #endif
 			}
 			catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested)

AMWD.Protocols.Modbus.Tcp/Extensions/StreamExtensions.cs

@@ -11,7 +11,7 @@ namespace System.IO
 			int offset = 0;
 			do
 			{
-				int count = await stream.ReadAsync(buffer, offset, expectedBytes - offset, cancellationToken).ConfigureAwait(false);
+				int count = await stream.ReadAsync(buffer, offset, expectedBytes - offset, cancellationToken);
 				if (count < 1)
 					throw new EndOfStreamException();
 

AMWD.Protocols.Modbus.Tcp/ModbusTcpClient.cs

@@ -40,9 +40,6 @@ namespace AMWD.Protocols.Modbus.Tcp
 			Protocol = new TcpProtocol();
 		}
 
-		/// <inheritdoc/>
-		public override IModbusProtocol Protocol { get; set; }
-
 		/// <inheritdoc cref="IModbusConnection.IdleTimeout"/>
 		public TimeSpan IdleTimeout
 		{

AMWD.Protocols.Modbus.Tcp/ModbusTcpConnection.cs

@@ -26,13 +26,17 @@ namespace AMWD.Protocols.Modbus.Tcp
 		private bool _isDisposed;
 		private readonly CancellationTokenSource _disposeCts = new();
 
+		private readonly TcpClientWrapperFactory _tcpClientFactory = new();
 		private readonly SemaphoreSlim _clientLock = new(1, 1);
-		private readonly TcpClientWrapper _tcpClient = new();
+		private TcpClientWrapper _tcpClient = null;
 		private readonly Timer _idleTimer;
 
 		private readonly Task _processingTask;
 		private readonly AsyncQueue<RequestQueueItem> _requestQueue = new();
 
+		private TimeSpan _readTimeout = TimeSpan.FromMilliseconds(1);
+		private TimeSpan _writeTimeout = TimeSpan.FromMilliseconds(1);
+
 		#endregion Fields
 
 		/// <summary>
@@ -58,15 +62,33 @@ namespace AMWD.Protocols.Modbus.Tcp
 		/// <inheritdoc/>
 		public virtual TimeSpan ReadTimeout
 		{
-			get => TimeSpan.FromMilliseconds(_tcpClient.ReceiveTimeout);
-			set => _tcpClient.ReceiveTimeout = (int)value.TotalMilliseconds;
+			get => _readTimeout;
+			set
+			{
+				if (value < TimeSpan.Zero)
+					throw new ArgumentOutOfRangeException(nameof(value));
+
+				_readTimeout = value;
+
+				if (_tcpClient != null)
+					_tcpClient.ReceiveTimeout = (int)value.TotalMilliseconds;
+			}
 		}
 
 		/// <inheritdoc/>
 		public virtual TimeSpan WriteTimeout
 		{
-			get => TimeSpan.FromMilliseconds(_tcpClient.SendTimeout);
-			set => _tcpClient.SendTimeout = (int)value.TotalMilliseconds;
+			get => _writeTimeout;
+			set
+			{
+				if (value < TimeSpan.Zero)
+					throw new ArgumentOutOfRangeException(nameof(value));
+
+				_writeTimeout = value;
+
+				if (_tcpClient != null)
+					_tcpClient.SendTimeout = (int)value.TotalMilliseconds;
+			}
 		}
 
 		/// <summary>
@@ -116,7 +138,6 @@ namespace AMWD.Protocols.Modbus.Tcp
 
 			try
 			{
-				_processingTask.Wait();
 				_processingTask.Dispose();
 			}
 			catch
@@ -124,7 +145,7 @@ namespace AMWD.Protocols.Modbus.Tcp
 
 			OnIdleTimer(null);
 
-			_tcpClient.Dispose();
+			_tcpClient?.Dispose();
 			_clientLock.Dispose();
 
 			while (_requestQueue.TryDequeue(out var item))
@@ -164,7 +185,7 @@ namespace AMWD.Protocols.Modbus.Tcp
 			{
 				Request = [.. request],
 				ValidateResponseComplete = validateResponseComplete,
-				TaskCompletionSource = new(),
+				TaskCompletionSource = new TaskCompletionSource<IReadOnlyList<byte>>(),
 				CancellationTokenSource = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken)
 			};
 
@@ -187,7 +208,7 @@ namespace AMWD.Protocols.Modbus.Tcp
 				try
 				{
 					// Get next request to process
-					var item = await _requestQueue.DequeueAsync(cancellationToken).ConfigureAwait(false);
+					var item = await _requestQueue.DequeueAsync(cancellationToken);
 
 					// Remove registration => already removed from queue
 					item.CancellationTokenRegistration.Dispose();
@@ -195,19 +216,19 @@ namespace AMWD.Protocols.Modbus.Tcp
 					// Build combined cancellation token
 					using var linkedCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken, item.CancellationTokenSource.Token);
 					// Wait for exclusive access
-					await _clientLock.WaitAsync(linkedCts.Token).ConfigureAwait(false);
+					await _clientLock.WaitAsync(linkedCts.Token);
 					try
 					{
 						// Ensure connection is up
-						await AssertConnection(linkedCts.Token).ConfigureAwait(false);
+						await AssertConnection(linkedCts.Token);
 
 						var stream = _tcpClient.GetStream();
-						await stream.FlushAsync(linkedCts.Token).ConfigureAwait(false);
+						await stream.FlushAsync(linkedCts.Token);
 
 #if NET6_0_OR_GREATER
-						await stream.WriteAsync(item.Request, linkedCts.Token).ConfigureAwait(false);
+						await stream.WriteAsync(item.Request, linkedCts.Token);
 #else
-						await stream.WriteAsync(item.Request, 0, item.Request.Length, linkedCts.Token).ConfigureAwait(false);
+						await stream.WriteAsync(item.Request, 0, item.Request.Length, linkedCts.Token);
 #endif
 
 						linkedCts.Token.ThrowIfCancellationRequested();
@@ -218,9 +239,9 @@ namespace AMWD.Protocols.Modbus.Tcp
 						do
 						{
 #if NET6_0_OR_GREATER
-							int readCount = await stream.ReadAsync(buffer, linkedCts.Token).ConfigureAwait(false);
+							int readCount = await stream.ReadAsync(buffer, linkedCts.Token);
 #else
-							int readCount = await stream.ReadAsync(buffer, 0, buffer.Length, linkedCts.Token).ConfigureAwait(false);
+							int readCount = await stream.ReadAsync(buffer, 0, buffer.Length, linkedCts.Token);
 #endif
 							if (readCount < 1)
 								throw new EndOfStreamException();
@@ -267,7 +288,7 @@ namespace AMWD.Protocols.Modbus.Tcp
 		// Has to be called within _clientLock!
 		private async Task AssertConnection(CancellationToken cancellationToken)
 		{
-			if (_tcpClient.Connected)
+			if (_tcpClient?.Connected == true)
 				return;
 
 			int delay = 1;
@@ -284,14 +305,16 @@ namespace AMWD.Protocols.Modbus.Tcp
 				{
 					foreach (var ipAddress in ipAddresses)
 					{
-						_tcpClient.Close();
+						_tcpClient?.Close();
+						_tcpClient?.Dispose();
 
+						_tcpClient = _tcpClientFactory.Create(ipAddress.AddressFamily, _readTimeout, _writeTimeout);
 #if NET6_0_OR_GREATER
-						using var connectTask = _tcpClient.ConnectAsync(ipAddress, Port, cancellationToken);
+						var connectTask = _tcpClient.ConnectAsync(ipAddress, Port, cancellationToken);
 #else
-						using var connectTask = _tcpClient.ConnectAsync(ipAddress, Port);
+						var connectTask = _tcpClient.ConnectAsync(ipAddress, Port);
 #endif
-						if (await Task.WhenAny(connectTask, Task.Delay(ReadTimeout, cancellationToken)) == connectTask)
+						if (await Task.WhenAny(connectTask, Task.Delay(_readTimeout, cancellationToken)) == connectTask)
 						{
 							await connectTask;
 							if (_tcpClient.Connected)
@@ -309,7 +332,7 @@ namespace AMWD.Protocols.Modbus.Tcp
 
 					try
 					{
-						await Task.Delay(TimeSpan.FromSeconds(delay), cancellationToken).ConfigureAwait(false);
+						await Task.Delay(TimeSpan.FromSeconds(delay), cancellationToken);
 					}
 					catch
 					{ /* keep it quiet */ }

AMWD.Protocols.Modbus.Tcp/ModbusTcpServer.cs

@@ -193,6 +193,8 @@ namespace AMWD.Protocols.Modbus.Tcp
 
 			_clients.Clear();
 			_devices.Clear();
+
+			_stopCts?.Dispose();
 		}
 
 		private void Assertions()
@@ -216,11 +218,11 @@ namespace AMWD.Protocols.Modbus.Tcp
 				try
 				{
 #if NET8_0_OR_GREATER
-					var client = await _listener.AcceptTcpClientAsync(cancellationToken).ConfigureAwait(false);
+					var client = await _listener.AcceptTcpClientAsync(cancellationToken);
 #else
-					var client = await _listener.AcceptTcpClientAsync().ConfigureAwait(false);
+					var client = await _listener.AcceptTcpClientAsync();
 #endif
-					await _clientListLock.WaitAsync(cancellationToken).ConfigureAwait(false);
+					await _clientListLock.WaitAsync(cancellationToken);
 					try
 					{
 						_clients.Add(client);
@@ -250,20 +252,20 @@ namespace AMWD.Protocols.Modbus.Tcp
 					using (var cts = new CancellationTokenSource(ReadWriteTimeout))
 					using (cancellationToken.Register(cts.Cancel))
 					{
-						byte[] headerBytes = await stream.ReadExpectedBytesAsync(6, cts.Token).ConfigureAwait(false);
+						byte[] headerBytes = await stream.ReadExpectedBytesAsync(6, cts.Token);
 						requestBytes.AddRange(headerBytes);
 
 						byte[] followingCountBytes = headerBytes.Skip(4).Take(2).ToArray();
 						followingCountBytes.SwapBigEndian();
 						int followingCount = BitConverter.ToUInt16(followingCountBytes, 0);
 
-						byte[] bodyBytes = await stream.ReadExpectedBytesAsync(followingCount, cts.Token).ConfigureAwait(false);
+						byte[] bodyBytes = await stream.ReadExpectedBytesAsync(followingCount, cts.Token);
 						requestBytes.AddRange(bodyBytes);
 					}
 
 					byte[] responseBytes = HandleRequest([.. requestBytes]);
 					if (responseBytes != null)
-						await stream.WriteAsync(responseBytes, 0, responseBytes.Length, cancellationToken).ConfigureAwait(false);
+						await stream.WriteAsync(responseBytes, 0, responseBytes.Length, cancellationToken);
 				}
 			}
 			catch
@@ -272,7 +274,7 @@ namespace AMWD.Protocols.Modbus.Tcp
 			}
 			finally
 			{
-				await _clientListLock.WaitAsync(cancellationToken).ConfigureAwait(false);
+				await _clientListLock.WaitAsync(cancellationToken);
 				try
 				{
 					_clients.Remove(client);

AMWD.Protocols.Modbus.Tcp/README.md

@@ -23,6 +23,18 @@ float voltage = registers.GetSingle();
 Console.WriteLine($"The voltage of device #{unitId} between L1 and N is: {voltage:N2}V");
 ```
 
+If you want to use the `RTU over TCP` protocol instead, you can do this on initialization:
+
+```csharp
+// [...]
+
+using var client = new ModbusTcpClient(host, port)
+{
+	Protocol = new RtuOverTcpProtocol();
+};
+
+// [...]
+```
 
 ## Sources
 

AMWD.Protocols.Modbus.Tcp/Utils/TcpClientWrapper.cs

@@ -8,11 +8,11 @@ namespace AMWD.Protocols.Modbus.Tcp.Utils
 {
 	/// <inheritdoc cref="TcpClient" />
 	[System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
-	internal class TcpClientWrapper : IDisposable
+	internal class TcpClientWrapper(AddressFamily addressFamily) : IDisposable
 	{
 		#region Fields
 
-		private readonly TcpClient _client = new();
+		private readonly TcpClient _client = new(addressFamily);
 
 		#endregion Fields
 

AMWD.Protocols.Modbus.Tcp/Utils/TcpClientWrapperFactory.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Net.Sockets;
+
+namespace AMWD.Protocols.Modbus.Tcp.Utils
+{
+	[System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
+	internal class TcpClientWrapperFactory
+	{
+		/// <summary>
+		/// Creates a new instance of <see cref="TcpClientWrapper"/>.
+		/// </summary>
+		/// <param name="addressFamily">The <see cref="AddressFamily"/> of the <see cref="TcpClient"/> to use.</param>
+		/// <param name="readTimeout">The read timeout.</param>
+		/// <param name="writeTimeout">The write timeout.</param>
+		/// <returns>A new <see cref="TcpClientWrapper"/> instance.</returns>
+		public virtual TcpClientWrapper Create(AddressFamily addressFamily, TimeSpan readTimeout, TimeSpan writeTimeout)
+		{
+			var client = new TcpClientWrapper(addressFamily)
+			{
+				ReceiveTimeout = (int)readTimeout.TotalMilliseconds,
+				SendTimeout = (int)writeTimeout.TotalMilliseconds
+			};
+			return client;
+		}
+	}
+}

AMWD.Protocols.Modbus.Tests/AMWD.Protocols.Modbus.Tests.csproj

@@ -13,7 +13,11 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="coverlet.msbuild" Version="6.0.1">
+    <PackageReference Include="coverlet.collector" Version="6.0.2">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+    </PackageReference>
+    <PackageReference Include="coverlet.msbuild" Version="6.0.2">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>

AMWD.Protocols.Modbus.Tests/Tcp/ModbusTcpConnectionTest.cs

@@ -1,6 +1,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Net;
+using System.Net.Sockets;
 using System.Reflection;
 using System.Threading;
 using System.Threading.Tasks;
@@ -16,6 +17,7 @@ namespace AMWD.Protocols.Modbus.Tests.Tcp
 		private readonly string _hostname = "127.0.0.1";
 
 		private Mock<TcpClientWrapper> _tcpClientMock;
+		private Mock<TcpClientWrapperFactory> _tcpClientFactoryMock;
 		private Mock<NetworkStreamWrapper> _networkStreamMock;
 
 		private bool _alwaysConnected;
@@ -40,10 +42,19 @@ namespace AMWD.Protocols.Modbus.Tests.Tcp
 		}
 
 		[TestMethod]
-		public void ShouldGetAndSetPropertiesOfBaseClient()
+		public async Task ShouldSetPropertiesOfBaseClient()
 		{
 			// Arrange
+			byte[] request = [1, 2, 3];
+			byte[] expectedResponse = [9, 8, 7];
+			var validation = new Func<IReadOnlyList<byte>, bool>(_ => true);
+			_networkResponseQueue.Enqueue(expectedResponse);
+
 			var connection = GetTcpConnection();
+			await connection.InvokeAsync(request, validation);
+
+			_tcpClientMock.Invocations.Clear();
+			_networkStreamMock.Invocations.Clear();
 
 			// Act
 			connection.ReadTimeout = TimeSpan.FromSeconds(123);
@@ -51,8 +62,8 @@ namespace AMWD.Protocols.Modbus.Tests.Tcp
 
 			// Assert - part 1
 			Assert.AreEqual("TCP", connection.Name);
-			Assert.AreEqual(1, connection.ReadTimeout.TotalSeconds);
-			Assert.AreEqual(1, connection.WriteTimeout.TotalSeconds);
+			Assert.AreEqual(123, connection.ReadTimeout.TotalSeconds);
+			Assert.AreEqual(456, connection.WriteTimeout.TotalSeconds);
 
 			Assert.AreEqual(_hostname, connection.Hostname);
 			Assert.AreEqual(502, connection.Port);
@@ -61,9 +72,6 @@ namespace AMWD.Protocols.Modbus.Tests.Tcp
 			_tcpClientMock.VerifySet(c => c.ReceiveTimeout = 123000, Times.Once);
 			_tcpClientMock.VerifySet(c => c.SendTimeout = 456000, Times.Once);
 
-			_tcpClientMock.VerifyGet(c => c.ReceiveTimeout, Times.Once);
-			_tcpClientMock.VerifyGet(c => c.SendTimeout, Times.Once);
-
 			_tcpClientMock.VerifyNoOtherCalls();
 			_networkStreamMock.VerifyNoOtherCalls();
 		}
@@ -173,6 +181,7 @@ namespace AMWD.Protocols.Modbus.Tests.Tcp
 			CollectionAssert.AreEqual(expectedResponse, response.ToArray());
 			CollectionAssert.AreEqual(request, _networkRequestCallbacks.First());
 
+			_tcpClientMock.Verify(c => c.ConnectAsync(It.IsAny<IPAddress>(), It.IsAny<int>(), It.IsAny<CancellationToken>()), Times.Once);
 			_tcpClientMock.Verify(c => c.Connected, Times.Once);
 			_tcpClientMock.Verify(c => c.GetStream(), Times.Once);
 
@@ -211,11 +220,10 @@ namespace AMWD.Protocols.Modbus.Tests.Tcp
 			CollectionAssert.AreEqual(expectedResponse, response.ToArray());
 			CollectionAssert.AreEqual(request, _networkRequestCallbacks.First());
 
-			_tcpClientMock.VerifyGet(c => c.ReceiveTimeout, Times.Once);
-
 			_tcpClientMock.Verify(c => c.Connected, Times.Exactly(3));
 			_tcpClientMock.Verify(c => c.Close(), Times.Exactly(2));
-			_tcpClientMock.Verify(c => c.ConnectAsync(It.IsAny<IPAddress>(), It.IsAny<int>(), It.IsAny<CancellationToken>()), Times.Once);
+			_tcpClientMock.Verify(c => c.Dispose(), Times.Once);
+			_tcpClientMock.Verify(c => c.ConnectAsync(It.IsAny<IPAddress>(), It.IsAny<int>(), It.IsAny<CancellationToken>()), Times.Exactly(2));
 			_tcpClientMock.Verify(c => c.GetStream(), Times.Once);
 
 			_networkStreamMock.Verify(ns => ns.FlushAsync(It.IsAny<CancellationToken>()), Times.Once);
@@ -289,11 +297,10 @@ namespace AMWD.Protocols.Modbus.Tests.Tcp
 			CollectionAssert.AreEqual(expectedResponse, response.ToArray());
 			CollectionAssert.AreEqual(request, _networkRequestCallbacks.First());
 
-			_tcpClientMock.VerifyGet(c => c.ReceiveTimeout, Times.Once);
-
 			_tcpClientMock.Verify(c => c.Connected, Times.Exactly(3));
 			_tcpClientMock.Verify(c => c.Close(), Times.Once);
-			_tcpClientMock.Verify(c => c.ConnectAsync(It.IsAny<IPAddress>(), It.IsAny<int>(), It.IsAny<CancellationToken>()), Times.Once);
+			_tcpClientMock.Verify(c => c.Dispose(), Times.Once);
+			_tcpClientMock.Verify(c => c.ConnectAsync(It.IsAny<IPAddress>(), It.IsAny<int>(), It.IsAny<CancellationToken>()), Times.Exactly(2));
 			_tcpClientMock.Verify(c => c.GetStream(), Times.Once);
 
 			_networkStreamMock.Verify(ns => ns.FlushAsync(It.IsAny<CancellationToken>()), Times.Once);
@@ -329,11 +336,10 @@ namespace AMWD.Protocols.Modbus.Tests.Tcp
 			CollectionAssert.AreEqual(expectedResponse, response.ToArray());
 			CollectionAssert.AreEqual(request, _networkRequestCallbacks.First());
 
-			_tcpClientMock.VerifyGet(c => c.ReceiveTimeout, Times.Exactly(2));
-
 			_tcpClientMock.Verify(c => c.Connected, Times.Exactly(3));
 			_tcpClientMock.Verify(c => c.Close(), Times.Exactly(2));
-			_tcpClientMock.Verify(c => c.ConnectAsync(It.IsAny<IPAddress>(), It.IsAny<int>(), It.IsAny<CancellationToken>()), Times.Exactly(2));
+			_tcpClientMock.Verify(c => c.Dispose(), Times.Exactly(2));
+			_tcpClientMock.Verify(c => c.ConnectAsync(It.IsAny<IPAddress>(), It.IsAny<int>(), It.IsAny<CancellationToken>()), Times.Exactly(3));
 			_tcpClientMock.Verify(c => c.GetStream(), Times.Once);
 
 			_networkStreamMock.Verify(ns => ns.FlushAsync(It.IsAny<CancellationToken>()), Times.Once);
@@ -426,6 +432,7 @@ namespace AMWD.Protocols.Modbus.Tests.Tcp
 			CollectionAssert.AreEqual(expectedResponse, response.ToArray());
 
 			_tcpClientMock.Verify(c => c.Connected, Times.Once);
+			_tcpClientMock.Verify(c => c.ConnectAsync(It.IsAny<IPAddress>(), It.IsAny<int>(), It.IsAny<CancellationToken>()), Times.Once);
 			_tcpClientMock.Verify(c => c.GetStream(), Times.Once);
 
 			_networkStreamMock.Verify(ns => ns.FlushAsync(It.IsAny<CancellationToken>()), Times.Once);
@@ -475,6 +482,7 @@ namespace AMWD.Protocols.Modbus.Tests.Tcp
 			CollectionAssert.AreEqual(request, _networkRequestCallbacks.First());
 
 			_tcpClientMock.Verify(c => c.Connected, Times.Once);
+			_tcpClientMock.Verify(c => c.ConnectAsync(It.IsAny<IPAddress>(), It.IsAny<int>(), It.IsAny<CancellationToken>()), Times.Once);
 			_tcpClientMock.Verify(c => c.GetStream(), Times.Once);
 			_tcpClientMock.Verify(c => c.Dispose(), Times.Once);
 
@@ -508,7 +516,7 @@ namespace AMWD.Protocols.Modbus.Tests.Tcp
 					return ValueTask.FromResult(0);
 				});
 
-			_tcpClientMock = new Mock<TcpClientWrapper>();
+			_tcpClientMock = new Mock<TcpClientWrapper>(AddressFamily.Unknown);
 			_tcpClientMock.Setup(c => c.Connected).Returns(() => _alwaysConnected || _connectedQueue.Dequeue());
 			_tcpClientMock.Setup(c => c.ReceiveTimeout).Returns(() => _clientReceiveTimeout);
 			_tcpClientMock.Setup(c => c.SendTimeout).Returns(() => _clientSendTimeout);
@@ -521,6 +529,11 @@ namespace AMWD.Protocols.Modbus.Tests.Tcp
 				.Setup(c => c.GetStream())
 				.Returns(() => _networkStreamMock.Object);
 
+			_tcpClientFactoryMock = new Mock<TcpClientWrapperFactory>();
+			_tcpClientFactoryMock
+				.Setup(c => c.Create(It.IsAny<AddressFamily>(), It.IsAny<TimeSpan>(), It.IsAny<TimeSpan>()))
+				.Returns(_tcpClientMock.Object);
+
 			var connection = new ModbusTcpConnection
 			{
 				Hostname = _hostname,
@@ -528,9 +541,9 @@ namespace AMWD.Protocols.Modbus.Tests.Tcp
 			};
 
 			// Replace real connection with mock
-			var connectionField = connection.GetType().GetField("_tcpClient", BindingFlags.NonPublic | BindingFlags.Instance);
-			(connectionField.GetValue(connection) as TcpClientWrapper)?.Dispose();
-			connectionField.SetValue(connection, _tcpClientMock.Object);
+			var factoryField = connection.GetType().GetField("_tcpClientFactory", BindingFlags.NonPublic | BindingFlags.Instance);
+			(factoryField.GetValue(connection) as TcpClientWrapper)?.Dispose();
+			factoryField.SetValue(connection, _tcpClientFactoryMock.Object);
 
 			return connection;
 		}

AMWD.Protocols.Modbus.sln

@@ -29,11 +29,13 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "build", "build", "{C8065AE3
 		Directory.Build.props = Directory.Build.props
 	EndProjectSection
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "AMWD.Protocols.Modbus.Tests", "AMWD.Protocols.Modbus.Tests\AMWD.Protocols.Modbus.Tests.csproj", "{146070C4-E922-4F5A-AD6F-9A899186E26E}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "AMWD.Protocols.Modbus.Tests", "AMWD.Protocols.Modbus.Tests\AMWD.Protocols.Modbus.Tests.csproj", "{146070C4-E922-4F5A-AD6F-9A899186E26E}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "AMWD.Protocols.Modbus.Tcp", "AMWD.Protocols.Modbus.Tcp\AMWD.Protocols.Modbus.Tcp.csproj", "{8C888A84-CD09-4087-B5DA-67708ABBABA2}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "AMWD.Protocols.Modbus.Tcp", "AMWD.Protocols.Modbus.Tcp\AMWD.Protocols.Modbus.Tcp.csproj", "{8C888A84-CD09-4087-B5DA-67708ABBABA2}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "AMWD.Protocols.Modbus.Serial", "AMWD.Protocols.Modbus.Serial\AMWD.Protocols.Modbus.Serial.csproj", "{D966826F-EE6C-4BC0-9185-C2A9A50FD586}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "AMWD.Protocols.Modbus.Serial", "AMWD.Protocols.Modbus.Serial\AMWD.Protocols.Modbus.Serial.csproj", "{D966826F-EE6C-4BC0-9185-C2A9A50FD586}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "AMWD.Protocols.Modbus.Proxy", "AMWD.Protocols.Modbus.Proxy\AMWD.Protocols.Modbus.Proxy.csproj", "{C30EBE45-E3B8-4997-95DF-8F94B31C8E1A}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -57,6 +59,10 @@ Global
 		{D966826F-EE6C-4BC0-9185-C2A9A50FD586}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{D966826F-EE6C-4BC0-9185-C2A9A50FD586}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{D966826F-EE6C-4BC0-9185-C2A9A50FD586}.Release|Any CPU.Build.0 = Release|Any CPU
+		{C30EBE45-E3B8-4997-95DF-8F94B31C8E1A}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{C30EBE45-E3B8-4997-95DF-8F94B31C8E1A}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{C30EBE45-E3B8-4997-95DF-8F94B31C8E1A}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{C30EBE45-E3B8-4997-95DF-8F94B31C8E1A}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

CHANGELOG.md

@@ -7,12 +7,28 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-_nothing changed yet_
+_no changes_
+
+
+## [v0.3.0] (2024-05-31)
+
+### Added
+
+- New `AMWD.Protocols.Modbus.Proxy` package, that contains the server implementations as proxies
+
+### Changed
+
+- Renamed `ModbusSerialServer` to `ModbusRtuServer` to clearify the protocol that is used
+- Made `Protocol` property of `ModbusClientBase` non-abstract
+
+### Fixed
+
+- Issue with missing client on TCP connection when using default constructor (seems that `AddressFamily.Unknown` caused the problem)
 
 
 ## [v0.2.0] (2024-04-02)
 
-First "final" re-implementation.
+First "final" re-implementation
 
 
 ## v0.1.0 (2022-08-28)
@@ -22,5 +38,6 @@ So this tag is only here for documentation purposes of the NuGet Gallery.
 
 
 
-[Unreleased]: https://github.com/AM-WD/AMWD.Protocols.Modbus/compare/v0.2.0...HEAD
+[Unreleased]: https://github.com/AM-WD/AMWD.Protocols.Modbus/compare/v0.3.0...HEAD
+[v0.3.0]: https://github.com/AM-WD/AMWD.Protocols.Modbus/compare/v0.2.0...v0.3.0
 [v0.2.0]: https://github.com/AM-WD/AMWD.Protocols.Modbus/tree/v0.2.0

README.md

@@ -4,7 +4,7 @@ Here you can find a basic implementation of the Modbus protocol.
 
 ## Overview
 
-The project is divided into three parts.
+The project is divided into four parts.
 
 To be mentioned at the beginning:    
 Only the clients are build very modular to fit any requirement reached on the first implementation back in 2018 ([see here]).    
@@ -20,6 +20,11 @@ For example the default protocol versions: `TCP`, `RTU` and `ASCII`.
 With this package you'll have anything you need to create your own client implementations.
 
 
+### [Proxy]
+
+The package contains a TCP and a RTU server implementation as proxy which contains a client of your choice to connect to.
+
+
 ### [Serial]
 
 This package contains some wrappers and implementations for the serial protocol.
@@ -42,6 +47,7 @@ Published under [MIT License] (see [**tl;dr**Legal])
 
 [see here]: https://github.com/andreasAMmueller/Modbus
 [Common]: AMWD.Protocols.Modbus.Common/README.md
+[Proxy]: AMWD.Protocols.Modbus.Proxy/README.md
 [Serial]: AMWD.Protocols.Modbus.Serial/README.md
 [TCP]: AMWD.Protocols.Modbus.Tcp/README.md
 [MIT License]: LICENSE.txt