submit.py

#!/usr/bin/env python
from telnetlib import Telnet
import sys

def submit(flag):
    t = Telnet("localhost", 8888)
    t.read_very_eager()

    t.write(flag)
    result = t.read_very_eager()
    if result == "nope...\n\n":
        print "no"
    elif result == "KTHXBYE!\n\n":
        print "yes"
    elif result == "U MAD?!\n\n":
        print "..."

    t.close()

if __name__ == '__main__':
    if sys.stdin.isatty():
        flags = sys.argv[1:]
    else:
        flags = [line[0:-1] for line in sys.stdin]

    for flag in flags:
        submit(flag)

submit_server.py

#!/usr/bin/env python
import socket

GREETING = """Welcome to teh awesome TUD submit server!
Please paste your flags!

"""
ADDRESS = ("127.0.0.1", 8888)

class SubmitServer():
    def __init__(self):
        self.FLAGLEN = 5
        self.flags = set()


    def _is_palindrome(self, flag):
        return flag == flag[::-1]

    def listen(self):
        self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.socket.bind(ADDRESS)
        self.socket.listen(23)
        print "Listening on %s:%d..." % ADDRESS

        while True:
            connection, address = self.socket.accept()
            connection.send(GREETING)
            msg = ''
            while len(msg) < self.FLAGLEN:
                chunk = connection.recv(self.FLAGLEN-len(msg))
                if chunk == '':
                    raise RuntimeError("socket connection broken")
                msg = msg + chunk
            print msg
            if self._is_palindrome(msg):
                if msg in self.flags:
                    connection.send("U MAD?!\n\n")
                else:
                    self.flags.add(msg)
                    connection.send("KTHXBYE!\n\n")
            else:
                connection.send("nope...\n\n")
            connection.close()


ss = SubmitServer()
ss.listen()