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C#里创建一个TCP客户端连接类

TCP客户端，一般分为两种，一种是同步收发数据，这种需要开发线程来处理。
如果连接比较多，就会消耗比较多线程。
另外一种，就是使用异步连接，这样只需要一个线程，就可以连接很多个。

在这里使用异步的方式来连接，例子的代码如下：
 

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;namespace ModbusTCP.Modbus
{class MyTcp : TcpClient{public delegate void Connect_Resp(); //声明委托public delegate void Recv_Resp(byte[] data); //声明委托private Connect_Resp _ConnectSucces;private Connect_Resp _ConnectFail;private Recv_Resp _Recv_Resp;public event Action _SendSuccess;public event Action _SendFail;internal class StateObject{public TcpClient client = null;public int totalBytesRead = 0;public const int BufferSize = 1024;public string readType = null;public byte[] buffer = new byte[BufferSize];public StringBuilder messageBuffer = new StringBuilder();}public string ErrorString { get; set; }public MyTcp(Connect_Resp con_succes, Connect_Resp con_fail, Recv_Resp recv){_ConnectSucces = con_succes;_ConnectFail = con_fail;_Recv_Resp = recv;}public void ClientConnect(string strIP, int port){BeginConnect(strIP, port, new AsyncCallback(ConnectCallback), this);}public virtual void ConnectCallback(IAsyncResult ar){MyTcp t = (MyTcp)ar.AsyncState;try{if (t != null && t.Client != null){t.EndConnect(ar);if (t.Connected){OnConnectSuccess(t);}else{OnConnectFailure("连接失败");}}else{OnConnectFailure("连接对象为空");}}catch (SocketException se){OnConnectFailure($"连接发生套接字错误: {se.SocketErrorCode} - {se.Message}");}catch (Exception ex){OnConnectFailure($"连接发生未知错误: {ex.Message}");}}private void OnConnectSuccess(MyTcp tcpClient){_ConnectSucces?.Invoke();AsyncRead(tcpClient);}private void OnConnectFailure(string errorMessage){ErrorString = errorMessage;_ConnectFail?.Invoke();}/// <summary>/// 异步读TCP数据/// </summary>/// <param name="sock"></param>private void AsyncRead(MyTcp sock){StateObject state = new StateObject{client = sock};NetworkStream stream = sock.GetStream();if (stream.CanRead){try{IAsyncResult ar = stream.BeginRead(state.buffer, 0, StateObject.BufferSize,new AsyncCallback(TCPReadCallBack), state);}catch (Exception e){ErrorString = "Network IO problem " + e.ToString();_ConnectFail?.Invoke();}}}/// <summary>/// TCP读数据的回调函数/// </summary>/// <param name="ar"></param>private void TCPReadCallBack(IAsyncResult ar){StateObject state = (StateObject)ar.AsyncState;//主动断开时if ((state.client == null) || (!state.client.Connected))return;NetworkStream nas = state.client.GetStream();try{int numberOfBytesRead = nas.EndRead(ar);if (numberOfBytesRead > 0){state.totalBytesRead += numberOfBytesRead;byte[] dd = new byte[numberOfBytesRead];Array.Copy(state.buffer, 0, dd, 0, numberOfBytesRead);//接收数据_Recv_Resp?.Invoke(dd);nas.BeginRead(state.buffer, 0, StateObject.BufferSize,new AsyncCallback(TCPReadCallBack), state);}else{//被动断开时 nas.Close();state.client.Close();nas = null;state = null;_ConnectFail?.Invoke();}}catch (Exception){nas = null;state = null;_ConnectFail?.Invoke();}}public void Send(byte[] buffer, int offset, int size){NetworkStream stream = GetStream();if (stream.CanWrite){stream.BeginWrite(buffer, offset, size, new AsyncCallback(TCPSendCallBack), this);}}private void TCPSendCallBack(IAsyncResult ar){try{MyTcp tcp = (MyTcp)ar.AsyncState;NetworkStream stream = tcp.GetStream();stream.EndWrite(ar);_SendSuccess?.Invoke();}catch (Exception ex){ErrorString = $"发送数据时发生错误: {ex.Message}";_SendFail?.Invoke();}}//组合两个缓冲区的数据，并产生一个新的缓冲区返回public static byte[] CombineBytes(byte[] firstBytes, int firstIndex, int firstLength,byte[] secondBytes, int secondIndex, int secondLength){MemoryStream ms = new MemoryStream();ms.Write(firstBytes, firstIndex, firstLength);ms.Write(secondBytes, secondIndex, secondLength);byte[] bytes = ms.ToArray();ms.Close();return bytes;}}
}