C#利用服务器实现客户端之间通信

先来讲述下我自己对于整个Socket通信过程的理解，毕竟初学，说错见谅，知道错了会改正~ 

首先在服务端新建一个serverSocket，对其进行初始化（一般包含AddressFamily:IP地址类型，SocketType:Socket传输数据方式，ProtoType:传输协议）; 

接着我们要设置server端要绑定的IP:port;然后开始监听，并设置最多同时监听多少个Client.

这时，服务端就在等待状态，直到某一个Client连接到这个ip:port上，这时serverSocket.Accept()工作，获得这个连接。（此时的连接是有地址信息的哦！记得保存） 

获得连接之后，server就可以和这个Client进行通信了,当加入第二个Client（我们称其为ClientB）时，Server接收到ClientB的消息，可以将这个消息转发给前一个Client（我们称其为ClientA），当受到ClientA的消息，也可以转发给ClientB。这样就实现了Clients之间的通信了。（重点在保存连接信息！！）

那么现在贴上代码讲解：

Server端代码 

namespace SocketServer{  class Program  {    private static byte[] result = new byte[1024];       static Socket serverSocket;    private static string client;    private static Socket clientSocket;    //我这里存了两个Client，因为自己电脑开了两个Client，不会有多的    //理论上应该开一个Socket[]来保存信息，最好用一个二元组将client的信息和连接绑定起来    //这样就可以实现断开连接后下次登陆还是可以识别是这个Client    private static Socket clientSocketA=null;    private static Socket clientSocketB=null;        static void Main(string[] args)    {      Program.SetPort(8885);    }    private static void SetPort(int port)    {      IPAddress ip = IPAddress.Parse("127.0.0.1");//set ip      serverSocket = new Socket(AddressFamily.InterNetwork,        SocketType.Stream, ProtocolType.Tcp);//initialize      serverSocket.Bind(new IPEndPoint(ip, port));//bind      serverSocket.Listen(10);      //进入监听状态      Console.WriteLine("监听{0}成功", serverSocket.LocalEndPoint.ToString());      //开启一个线程来监听客户端连接      Thread myThread = new Thread(ListenClientConnect);      myThread.Start();      Console.ReadLine();    }    /// <summary>    /// 监听客户端连接    /// </summary>    private static void ListenClientConnect()    {      while (true)      {        //Client连接上后 得到这个连接        clientSocket = serverSocket.Accept();        //这里我因为只有两个Client，所以就简单写了        if (clientSocketA == null)        {          clientSocketA = clientSocket;        }        else if (clientSocketB == null)        {          clientSocketB = clientSocket;        }        else        {          //当其中一个断开了，又重新连接时，需要再次保存连接          if (clientSocketB.IsBound)          {            clientSocketA = clientSocketB;            clientSocketB = clientSocket;          }          else          {            clientSocketB = clientSocketA;            clientSocketA = clientSocket;          }                  }        clientSocket.Send(Encoding.ASCII.GetBytes("say hello"));        //开个线程接收Client信息        Thread receivedThread = new Thread(ReceiveMessage);        receivedThread.Start(clientSocket);      }    }       private static void ReceiveMessage(object clientSocket)    {      Socket myClientSocket = (Socket) clientSocket;            while (true)      {        try        {          int revceiveNumber = myClientSocket.Receive(result);          //Console.WriteLine("接受客户端{0}消息{1}", myClientSocket.RemoteEndPoint.ToString()          //  , Encoding.ASCII.GetString(result, 0, revceiveNumber));          Console.WriteLine(Encoding.ASCII.GetString(result, 0, revceiveNumber));          if (myClientSocket == clientSocketA)          {            Console.WriteLine("receive from A");            if (clientSocketB!=null&&clientSocketB.IsBound)            {              Console.WriteLine("a IS BOUND");              clientSocketB.Send(result, 0, revceiveNumber, SocketFlags.None);            }            else            {              myClientSocket.Send(Encoding.ASCII.GetBytes("the people is not online! Send Failed!"));              Console.WriteLine("对方不在线上，发送失败！");            }          }          else          {            Console.WriteLine("receive from B");            if (clientSocketA != null && clientSocketA.IsBound)            {              Console.WriteLine("a IS BOUND");              clientSocketA.Send(result, 0, revceiveNumber, SocketFlags.None);            }              else            {              myClientSocket.Send(Encoding.ASCII.GetBytes("the people is not online! Send Failed!"));              Console.WriteLine("对方不在线上，发送失败！");            }          }                  }        catch(Exception ex)        {          Console.WriteLine(ex.Message);          myClientSocket.Shutdown(SocketShutdown.Both);          myClientSocket.Close();          break;        }      }    }  }}