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，發送失敗！");
 }
 }
 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("連接失敗！");
 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();
 }
 }
}