C＃检测客户端与服务器的断开连接

Question

I've got a server and 2 winform clients(for a tictactoegame). Can I detect a client disconnection instantly ?. First opened client is player1 socket and 2nd is player2. Once both clients are connected player1 has to click a button and player2 buttons are all disabled. After player1 clicks a button player2buttons are enabled and player1 buttons disabled...so on

isConnected method

public  bool IsConnected(Socket socket)
{
    try
    {
        return !(socket.Poll(1, SelectMode.SelectRead) && socket.Available == 0);
    }
    catch (SocketException) { return false; }
}

Server code

public class ServerApp
{
    public Socket serverSocket;

    Socket player1;
    Socket player2;
    ServerGame myGame;

    public ServerApp()
    {
        myGame = new ServerGame();
        serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, 
                                  ProtocolType.Tcp);
        IPEndPoint ipLocal = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 8221);
        serverSocket.Bind(ipLocal);
        serverSocket.Listen(4);

        Console.WriteLine("Waiting for clients ...");
        player1 = serverSocket.Accept();
        Console.WriteLine("Player 1 joined");
        player2 = serverSocket.Accept();
        Console.WriteLine("Player 2 joined");

        myGame.InitGame();

        while (true)
        {
            try
            {
                myGame.Display();
                Console.WriteLine();

                myGame.Send(player1, BaseGame.Player.One);
                myGame.Send(player2, BaseGame.Player.Two);

                if (myGame.GetActivePlayer() == BaseGame.Player.One && 
                    myGame.IsConnected(player1)==true)
                {
                    myGame.Receive(player1);                       
                }
                else if(myGame.IsConnected(player1) == true)
                {
                    myGame.Receive(player2);
                }
            }
            catch(Exception e)
            {
                Console.WriteLine(e);
                Thread.Sleep(1000);                    
            }
        }

        Console.WriteLine("Server going down");
        Thread.Sleep(2000);
    }
}

class Program
{
    static void Main(string[] args)
    {
        ServerApp serverApp = new ServerApp();
    }
}

Answer 1

The player being closed should gracefully shutdown the socket before exiting. This involves calling Socket.Shutdown(SocketShutdown.Send) , and then waiting for a receive operation to return a byte count of 0 (indicating the remote client has also shutdown).

This will ensure timely closure of the connection. Otherwise, the other player not being closed will have no way to know that the connection was lost until they attempt to send some data.