c# - Listening for an Ethernet Cable Unplugging Event for a TCP Server Application

Question

I have a C# TCP server application. I detect disconnections of TCP clients when they disconnect from server but how can I detect a cable unplug event? When I unplug the ethernet cable I can't detect the disconnection.

Answer 1

You might want to apply "pinging" functionality, that will fail if there is TCP connection lose. Use this code to add extension method to Socket:

using System.Net.Sockets;

namespace Server.Sockets {
    public static class SocketExtensions {
        public static bool IsConnected(this Socket socket) {
            try {
                return !(socket.Poll(1, SelectMode.SelectRead) && socket.Available == 0);
            } catch(SocketException) {
                return false;
            }
        }
    }
}

Method will return false if there is no connection available. It should work to check if there is or no connection even if you had no SocketExceptions on Reveice / Send methods. Bear in mind that if you had exception that had error message that is related to connection lose, then you don't need check for connection anymore.
This method is meant to be used when socket is looks like connected but might be not like in your case.

Usage:

if (!socket.IsConnected()) {
    /* socket is disconnected */
}