namespace SocketServer{  class Program  {    private static byte[] result = new byte[1024];       static Socket serverSocket;    private static string client;    private static Socket clientSocket;    //我這里存了兩個Client，因為自己電腦開了兩個Client，不會有多的    //理論上應該開一個Socket[]來保存信息，最好用一個二元組將client的信息和連接綁定起來    //這樣就可以實現斷開連接后下次登陸還是可以識別是這個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);      //進入監聽狀態      Console.WriteLine("監聽{0}成功", serverSocket.LocalEndPoint.ToString());      //開啟一個線程來監聽客戶端連接      Thread myThread = new Thread(ListenClientConnect);      myThread.Start();      Console.ReadLine();    }    /// <summary>    /// 監聽客戶端連接    /// </summary>    private static void ListenClientConnect()    {      while (true)      {        //Client連接上后 得到這個連接        clientSocket = serverSocket.Accept();        //這里我因為只有兩個Client，所以就簡單寫了        if (clientSocketA == null)        {          clientSocketA = clientSocket;        }        else if (clientSocketB == null)        {          clientSocketB = clientSocket;        }        else        {          //當其中一個斷開了，又重新連接時，需要再次保存連接          if (clientSocketB.IsBound)          {            clientSocketA = clientSocketB;            clientSocketB = clientSocket;          }          else          {            clientSocketB = clientSocketA;            clientSocketA = clientSocket;          }                  }        clientSocket.Send(Encoding.ASCII.GetBytes("say hello"));        //開個線程接收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("接受客戶端{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("對方不在線上，發送失??！");            }          }          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("對方不在線上，發送失敗！");            }          }                  }        catch(Exception ex)        {          Console.WriteLine(ex.Message);          myClientSocket.Shutdown(SocketShutdown.Both);          myClientSocket.Close();          break;        }      }    }  }}

namespace SocketClient{  class Program  {    private static byte[] result = new byte[1024];    private static Socket clientSocket;    private static void ListenServer()    {      while (true)      {        result = new byte[1024];        int receiveLength = clientSocket.Receive(result);                Console.WriteLine("{0}", Encoding.ASCII.GetString(result, 0, receiveLength));      }          }    static void Main(string[] args)    {      IPAddress ip = IPAddress.Parse("127.0.0.1");      clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);      try      {        clientSocket.Connect(ip, 8885);        Console.WriteLine("連接成功！");      }      catch (Exception e)      {        Console.WriteLine("連接失??！");        return;      }      Thread threadRead = new Thread(ListenServer);      threadRead.Start();           while(true)      {        try        {          Thread.Sleep(1000);          string sendMessage = Console.ReadLine();          clientSocket.Send(Encoding.ASCII.GetBytes("Sylvia:"+sendMessage));                  }        catch (Exception ex)        {          clientSocket.Shutdown(SocketShutdown.Both);          clientSocket.Close();          break;        }      }      Console.WriteLine("發送完畢 按回車退出");      Console.ReadKey();    }  }}