feat: Introduce TcpClientFactory

Allows injecting custom TcpClient for monitoring and logging

Author: Christoph Seiler

S7.Net.UnitTest/ConnectionCloseTest.cs

@@ -1,11 +1,10 @@
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using System;
 using System.IO;
-using System.Linq;
-using System.Net.Sockets;
 using System.Reflection;
 using System.Threading;
 using System.Threading.Tasks;
+using S7.Net.Tcp;
 
 namespace S7.Net.UnitTest
 {
@@ -92,7 +91,7 @@ public async Task Test_CancellationDuringTransmission()
             }
 
             // Set a value to tcpClient field so we can later ensure that it has been closed.
-            tcpClientField.SetValue(plc, new TcpClient());
+            tcpClientField.SetValue(plc, new TcpClientWrapper());
             var tcpClientValue = tcpClientField.GetValue(plc);
             Assert.IsNotNull(tcpClientValue);
 
@@ -147,7 +146,7 @@ public async Task Test_CancellationBeforeTransmission()
             }
 
             // Set a value to tcpClient field so we can later ensure that it has been closed.
-            tcpClientField.SetValue(plc, new TcpClient());
+            tcpClientField.SetValue(plc, new TcpClientWrapper());
             var tcpClientValue = tcpClientField.GetValue(plc);
             Assert.IsNotNull(tcpClientValue);
 

S7.Net/PLC.cs

@@ -5,6 +5,7 @@
 using System.Net.Sockets;
 using S7.Net.Internal;
 using S7.Net.Protocol;
+using S7.Net.Tcp;
 using S7.Net.Types;
 
 
@@ -27,8 +28,11 @@ public partial class Plc : IDisposable
 
         private readonly TaskQueue queue = new TaskQueue();
 
+        private readonly ITcpClientFactory _tcpClientFactory;
+
         //TCP connection to device
-        private TcpClient? tcpClient;
+        private ITcpClient? tcpClient;
+
         private NetworkStream? _stream;
 
         private int readTimeout = DefaultTimeout; // default no timeout
@@ -124,8 +128,9 @@ public int WriteTimeout
         /// <param name="rack">rack of the PLC, usually it's 0, but check in the hardware configuration of Step7 or TIA portal</param>
         /// <param name="slot">slot of the CPU of the PLC, usually it's 2 for S7300-S7400, 0 for S7-1200 and S7-1500.
         ///  If you use an external ethernet card, this must be set accordingly.</param>
-        public Plc(CpuType cpu, string ip, Int16 rack, Int16 slot)
-            : this(cpu, ip, DefaultPort, rack, slot)
+        /// <param name="tcpClientFactory">Factory to provide the underlying <see cref="ITcpClient"/> for network communication.</param>
+        public Plc(CpuType cpu, string ip, Int16 rack, Int16 slot, ITcpClientFactory? tcpClientFactory = null)
+            : this(cpu, ip, DefaultPort, rack, slot, tcpClientFactory)
         {
         }
 
@@ -141,8 +146,9 @@ public Plc(CpuType cpu, string ip, Int16 rack, Int16 slot)
         /// <param name="rack">rack of the PLC, usually it's 0, but check in the hardware configuration of Step7 or TIA portal</param>
         /// <param name="slot">slot of the CPU of the PLC, usually it's 2 for S7300-S7400, 0 for S7-1200 and S7-1500.
         ///  If you use an external ethernet card, this must be set accordingly.</param>
-        public Plc(CpuType cpu, string ip, int port, Int16 rack, Int16 slot)
-            : this(ip, port, TsapPair.GetDefaultTsapPair(cpu, rack, slot))
+        /// <param name="tcpClientFactory">Factory to provide the underlying <see cref="ITcpClient"/> for network communication.</param>
+        public Plc(CpuType cpu, string ip, int port, Int16 rack, Int16 slot, ITcpClientFactory? tcpClientFactory = null)
+            : this(ip, port, TsapPair.GetDefaultTsapPair(cpu, rack, slot), tcpClientFactory)
         {
             if (!Enum.IsDefined(typeof(CpuType), cpu))
                 throw new ArgumentException(
@@ -162,7 +168,9 @@ public Plc(CpuType cpu, string ip, int port, Int16 rack, Int16 slot)
         /// </summary>
         /// <param name="ip">Ip address of the PLC</param>
         /// <param name="tsapPair">The TSAP addresses used for the connection request.</param>
-        public Plc(string ip, TsapPair tsapPair) : this(ip, DefaultPort, tsapPair)
+        /// <param name="tcpClientFactory">Factory to provide the underlying <see cref="ITcpClient"/> for network communication.</param>
+        public Plc(string ip, TsapPair tsapPair, ITcpClientFactory? tcpClientFactory = null)
+            : this(ip, DefaultPort, tsapPair, tcpClientFactory)
         {
         }
 
@@ -173,7 +181,8 @@ public Plc(string ip, TsapPair tsapPair) : this(ip, DefaultPort, tsapPair)
         /// <param name="ip">Ip address of the PLC</param>
         /// <param name="port">Port number used for the connection, default 102.</param>
         /// <param name="tsapPair">The TSAP addresses used for the connection request.</param>
-        public Plc(string ip, int port, TsapPair tsapPair)
+        /// <param name="tcpClientFactory">Factory to provide the underlying <see cref="ITcpClient"/> for network communication.</param>
+        public Plc(string ip, int port, TsapPair tsapPair, ITcpClientFactory? tcpClientFactory = null)
         {
             if (string.IsNullOrEmpty(ip))
                 throw new ArgumentException("IP address must valid.", nameof(ip));
@@ -182,6 +191,7 @@ public Plc(string ip, int port, TsapPair tsapPair)
             Port = port;
             MaxPDUSize = 240;
             TsapPair = tsapPair;
+            _tcpClientFactory = tcpClientFactory ?? new TcpClientWrapperFactory();
         }
 
         /// <summary>

S7.Net/PlcAsynchronous.cs

@@ -46,7 +46,7 @@ await queue.Enqueue(async () =>
 
         private async Task<NetworkStream> ConnectAsync(CancellationToken cancellationToken)
         {
-            tcpClient = new TcpClient();
+            tcpClient = _tcpClientFactory.Create();
             ConfigureConnection();
 
 #if NET5_0_OR_GREATER

S7.Net/Tcp/ITcpClient.cs

@@ -0,0 +1,21 @@
+using System.Net.Sockets;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace S7.Net.Tcp
+{
+    public interface ITcpClient
+    {
+        public int ReceiveTimeout { get; set; }
+
+        public int SendTimeout { get; set; }
+
+        public bool Connected { get; }
+
+        public void Close();
+
+        public Task ConnectAsync(string ip, int port, CancellationToken cancellationToken = default);
+
+        public NetworkStream GetStream();
+    }
+}

S7.Net/Tcp/ITcpClientFactory.cs

@@ -0,0 +1,6 @@
+namespace S7.Net.Tcp;
+
+public interface ITcpClientFactory
+{
+    ITcpClient Create();
+}

S7.Net/Tcp/TcpClientWrapper.cs

@@ -0,0 +1,24 @@
+using System.Net.Sockets;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace S7.Net.Tcp;
+
+internal class TcpClientWrapper : TcpClient, ITcpClient
+{
+    public async Task ConnectAsync(string ip, int port, CancellationToken cancellationToken)
+    {
+#if NET5_0_OR_GREATER
+        await base.ConnectAsync(ip, port, cancellationToken).ConfigureAwait(false);
+#else
+        await base.ConnectAsync(ip, port).ConfigureAwait(false);
+#endif
+    }
+
+    public void Close()
+    {
+#if NET20_OR_GREATER
+        base.Close();
+#endif
+    }
+}

S7.Net/Tcp/TcpClientWrapperFactory.cs

@@ -0,0 +1,9 @@
+namespace S7.Net.Tcp;
+
+internal class TcpClientWrapperFactory : ITcpClientFactory
+{
+    public ITcpClient Create()
+    {
+        return new TcpClientWrapper();
+    }
+}