TCP/IP server using a main loop

echo_server.py

# adapted from http://roscidus.com/desktop/node/413

import socket
import gobject

def server(host, port):
    '''Initialize server and start listening.'''
    sock = socket.socket()
    sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    sock.bind((host, port))
    sock.listen(1)
    print "Listening..."
    gobject.io_add_watch(sock, gobject.IO_IN, listener)

def listener(sock, *args):
    '''Asynchronous connection listener. Starts a handler for each connection.'''
    conn, addr = sock.accept()
    print "Connected"
    gobject.io_add_watch(conn, gobject.IO_IN, handler)
    return True

def handler(conn, *args):
    '''Asynchronous connection handler. Processes each line from the socket.'''
    line = conn.recv(4096)
    if len(line) > 0:
        print "Received", line
        conn.send(line + "!!!")
        return True
    else:
        print "Connection closed."
        return False

def client(host, port):
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect((host, port))
    sock.send('Hello, world')
    data = sock.recv(1024)
    print data
    sock.close()

import sys

if sys.argv[1] == "server":
    server('', 50007)
    gobject.MainLoop().run()
else:
    client('', 50007)