How to detect closed TCP connection when client disconnected disgracfully ?

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How to detect closed TCP connection when Client disconnected disgracfully i.e sudden power off ?

Following method don't work when client disconnects disgracefully.

What I have tried:

C#

<pre>if (socket != null)
                    {
                        bool part1 = socket.Poll(1000, SelectMode.SelectRead);
                        bool part2 = (socket.Available == 0);
                        if (part1 && part2)
                        {
                            return false;
                        }
                        else
                        {
                            return true;
                        }
                    }
                    else
                        return false;

Posted 23-Apr-19 20:09pm

DoingWork

Updated 23-Apr-19 20:54pm

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User 11060979 · Answer 1 · 2019-04-23T20:55:00

Solution 2

TCP keepalive
These looks promising, answer 3 in .net - Instantly detect client disconnection from server socket - Stack Overflow[^]

and also here: http://tldp.org/HOWTO/TCP-Keepalive-HOWTO/overview.html[^]

I hope it helps.

Posted 23-Apr-19 20:55pm

User 11060979

Comments

DoingWork 14-May-19 0:54am

Keep Alive mode solves 50%. But if dont have option to make client as Keep Alive then what will be option?

RickZeeland · Answer 2 · 2019-04-23T20:34:00

Solution 1

I used something like this:

bool connectedLocal = true;

using (var socketTemp = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
 {
     socketTemp.Connect(ip, port);

     // Loop until prg finished or connection is lost.
     while (Running && connectedLocal)
     {
         Thread.CurrentThread.Join(100);
         connectedLocal = !(socketTemp.Poll(0, SelectMode.SelectRead) && socketTemp.Available == 0);
     }

     socketTemp.Close();
}

Posted 23-Apr-19 20:34pm

RickZeeland

Updated 23-Apr-19 20:37pm

v2

Comments

DoingWork 24-Apr-19 2:44am

It fails when connected client disconnects disgracefully. i.e. fail to send disconnect to network due to power shutdown.

RickZeeland 24-Apr-19 3:33am

That's strange, in our network it works as expected, maybe it has something to do with your network configuration ?