Simple TCP server which should emuale iteraction with jury server on challenges like RuCTF(I use it for testing flag posting script)

jury_emulator.py

#!/usr/bin/env python2
# -*- coding: utf-8 -*-

# Copyright::MichaelMayorov([email protected])

"""
I found example TCP server somewhere in Internet and quickly adapted it to
emulate jury flag receiving service on competitions like RuCTF(e)

I didn't test it too long.
"""

import socket, threading
import os
import sys
import signal

def handler(signum, frame):
    print "Stopping, disconnecting clients..."
    lock.acquire()
    for client in clients:
        client.socket.shutdown(socket.SHUT_RDWR)
        client.socket.close()
        print '%s:%s disconnected.' % client.address
#        clients.remove(client)
    lock.release()
    sys.exit(0)

signal.signal(signal.SIGINT, handler)

HOST = '127.0.0.1'
PORT = 31337

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind((HOST, PORT))
s.listen(4)
clients = [] #list of clients connected
lock = threading.Lock()


class chatServer(threading.Thread):
    def __init__(self, (socket,address)):
        threading.Thread.__init__(self)
        self.socket = socket
        self.address= address

    def run(self):

        def disconect(self):
            self.socket.close()
            print '%s:%s disconnected.' % self.address
            lock.acquire()
            clients.remove(self)
            lock.release()
            return

        lock.acquire()
        clients.append(self)
        lock.release()
        print '%s:%s connected.' % self.address
        self.socket.send("Enter team number:\n")
        tn = self.socket.recv(3)
        try:
            tn = int(tn.strip())
        except:
            self.socket.send("WRONG\n")
            disconnect(self)
        print "Team number:\n", tn
        self.socket.send("Welcome, team %d\n" % tn)
        while True:
            try:
                data = self.socket.recv(1024)
            except socket.error:
                break
            print "Receiving flag", data
            if int(os.urandom(5).encode('hex'),16) % 2:
                print "Flag incorrect"
                self.socket.send("TOO OLD: %s\n" % data)
                continue
            print "Flag correct"
            self.socket.send("OK: %s\n" % data)
        disconnect(self)

while True: # wait for socket to connect
    # send socket to chatserver and start monitoring
    t = chatServer(s.accept())
    t.daemon = True
    t.start()