TCP连接C#中Socket的正确初始化和配置

Question

I have a question regarding the following code:

    private static readonly Socket serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
        private static readonly List<Socket> clientSockets = new List<Socket>();
        private const int BUFFER_SIZE = 1024*2;
        private static readonly byte[] buffer = new byte[BUFFER_SIZE];
        public static Manager Manager { get; set; }
        private static bool firstInit = true;

        /// <summary>
        /// Config and start the server
        /// </summary>
        public static void SetupServer()
        {
            try
            {
                Manager.PCForm.ConnectionButtonStatus(false);
                var PORT = int.Parse(Properties.Settings.Default.LocalPort);
                var listenToAny = Properties.Settings.Default.ListenToAny;
                var IP = GetSocketIP(listenToAny);

                Logger.LogInfo("Setting up server...");

                if(Properties.Settings.Default.UseLocalWifiNetwork)
                {
                    Logger.LogInfo("PC Local IP: " + LocalIPAddress);
                }
                else
                {
                    Logger.LogInfo("PC External IP: " + ExternalIPAddress);
                }           

                if(firstInit)
                {
                    firstInit = false;
                    Logger.LogDebug("Binding new port:" + PORT);
                    serverSocket.Bind(new IPEndPoint(IP, PORT));
                }
                else
                {
                    Logger.LogDebug("Using port that was already binded");
                }

                serverSocket.Listen(0);
                Logger.LogDebug("Listening To: " + IP + ":" + PORT);
                serverSocket.BeginAccept(AcceptCallback, null);
                Manager.PCForm.ConnectionButtonStatus(true);
                Logger.LogInfo("Server setup complete");
            }
            catch(Exception ex)
            {
                FormsHelpers.ShowErrorMessage(ex.Message);
                Logger.LogError("Fail to setup server. Please restart the app.");
            }
        }

   public static void CloseAllSockets()
        {
            try
            {
                Logger.LogDebug("Closing All Sockets...");
                Manager.PCForm.ConnectionButtonStatus(false);
                foreach(Socket socket in clientSockets.ToArray())
                {
                    CloseSocket(socket);
                }

                serverSocket.Close();
                Logger.LogInfo("Server was shutdown");
                Manager.PCForm.ConnectionButtonStatus(true);
            }
            catch(Exception ex)
            {
                Console.WriteLine("Fail to close sockets.\r\nExpection: " + ex.Message);
            }
        }

My problem started when I wanted to reuse a bound socket. My application supports closing and reopens TCP connection in the server (It can be the same port or a new one).

Scenario:

1. The user starts the server (open a TCP socket in local IP and port 5000.

2. The user stops the server (The server closes the clients TCP connection and server socket)

3. The user starts the server again (same port - 5000 or new port if the user changed the port in app settings).

When the user starts the server again with the same port (5000) I get the error: Cannot access a disposed object: When the user starts the server again with a new port (5001) I get the error. invalid argument (because the server socket was bound to a different port).

If I remove the code serverSocket.Close(); it will work because only without changing the port because of the fact that the server socket was never closed. Look the netstat in that case:

But this is not good because it doesn't allow to change the port unless the configuration is saved and the user restarts the application.

Answer 1

I updated the code. When I shut down the server I only disconnect the clients. when I start the server I reuse the last socket but if I change the port I will close it and allocate a new instance of the socketServer and use it.

  if(portInUse.Equals(PORT))
                {
                    Logger.LogDebug("Using port that was already binded");
                }
                else
                {
                    Logger.LogDebug("Binding new port:" + PORT);

                    if(serverSocket != null)
                    {
                        //close previous socket because it was using old port
                        serverSocket.Close();
                    }

                    serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
                    serverSocket.Bind(new IPEndPoint(IP, PORT));
                    portInUse = PORT;
                }