Using KeyboardInterrupt with Sockets

[Samji]

Hi, everyone.

I'm trying to write a Python server application which listens on a port, but I also want the server to be to be terminated by pressing Ctrl+C (also Ctrl+Z on Windows).

I've tried using the KeyboardInterrupt exception handler to do this.
It works fine with this program.

# Proof of concept: exit on interrupt using KeyboardInterrupt exception
import sys

def test():
    try:
        i = 0
        while i < 100000000:
            print(i)
            i += 1
    except KeyboardInterrupt:
        print('This is stupid...')
        sys.exit(0)
        
test()

But not with this.

"""
Echo server to test interrupts
"""
import sys
import socket

class EchoServer:
    def __init__(self, port=1000):
        print(__doc__)
        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        s.bind(('', port))
        s.listen(1)
        conn, addr = s.accept()
        while 1:
            try:
                chunk = conn.recv(1024)
                print(chunk)
                conn.send(chunk)
            # I want the server to terminate when Ctrl-C/Z is pressed
            except KeyboardInterrupt: 
                conn.close()
                sys.exit(0)
                
        conn.close()
        sys.exit(0)
        
if __name__ == '__main__': EchoServer()

I also tried it with signal interrupt (signal module), the simple counter program worked fine too. But not this. Any ideas? I would guess it's something to do with how Python's sockets work. But surely there must be a way to interrupt the listen loop with Ctrl+C, right?

Thanks.

[Plagman]

The difference between your two examples is that the first one is spinning whereas the second one probably blocks waiting for data in conn.recv(). If you connect a client and start sending a bunch of data, your exception will start working. Try setting your socket to non-blocking mode in order to busy-wait checking for both socket and keyboard input. I'm sure python provides something similar to select() in order to wait more efficiently.

[Samji]

Thanks. I think you're right. I'll have a look at the documentation.

[Samji]

Thanks. I got it working in the end using Threads. http://vark.com/t/2981ec