Question

I’m using the following TCP communication code(server side) to handle the timeout etc…
If I kill the client side software than an exception happens(socket.error), but when I unplug the ethernet cable from client PC than only the socket.timeout exception happens, so how can I know that the connection is broken? Is that possible that I will get a socket.error exception after some minutes? I tried with 3minutes but I haven’t got the socket.error exception.

self.request.settimeout( 1 )
while 1:
        try:
            response = self.request.recv( buffSize )            
            if(response)
                ...response handler....       
            else:               
                ...disconnect handler....
        except socket.timeout :                  
            ...timeout handler...
        except socket.error:
            ...disconnect handler...

Answer 1

It depends on how quickly you want to detect the broken connection. If you are willing to wait a few minutes, you can turn on TCP Keepalive (https://www.rfc-editor.org/rfc/rfc1122#page-101):

import socket
self.request.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)

Note, the actual time interval used by TCP is operating system dependent.

If you need something faster than what TCP Keepalive offers, you probably need to introduce a "ping" feature to your protocol. What this means is your client and server periodically exchange a message that is a null operation. It just tests that the connection is alive.