Python P2P Sockets Chat Script working only on hom

Question

I have the following python script (a bit inefficient, I know) for a P2P chat program using sockets:

#!usr/bin/env python

import socket import threading import select import time import datetime

def main():

    class Chat_Server(threading.Thread):
            def __init__(self):
                threading.Thread.__init__(self)
                self.running = 1
                self.conn = None
                self.addr = None
            def run(self):
                HOST = ''
                PORT = 23647
                s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
                s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
                s.bind((HOST,PORT))
                s.listen(1)
                self.conn, self.addr = s.accept()
                # Select loop for listen
                while self.running == True:
                    inputready,outputready,exceptready \
                      = select.select ([self.conn],[self.conn],[])
                    for input_item in inputready:
                        # Handle sockets
                        message = self.conn.recv(1024)
                        if message:
                            print "Daniel: " + message + ' (' + datetime.datetime.now().strftime('%H:%M:%S') + ')'
                        else:
                            break
                    time.sleep(0)
            def kill(self):
                self.running = 0

    class Chat_Client(threading.Thread):
            def __init__(self):
                threading.Thread.__init__(self)
                self.host = None
                self.sock = None
                self.running = 1
            def run(self):
                PORT = 23647
                self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
                self.sock.connect((self.host, PORT))
                # Select loop for listen
                while self.running == True:
                    inputready,outputready,exceptready \
                      = select.select ([self.sock],[self.sock],[])
                    for input_item in inputready:
                        # Handle sockets
                        message = self.sock.recv(1024)
                        if message:
                            print "Daniel: " + message + ' (' + datetime.datetime.now().strftime('%H:%M:%S') + ')'
                        else:
                            break
                    time.sleep(0)
            def kill(self):
                self.running = 0

    class Text_Input(threading.Thread):
            def __init__(self):
                threading.Thread.__init__(self)
                self.running = 1
            def run(self):
                while self.running == True:
                  text = raw_input('')
                  try:
                      chat_client.sock.sendall(text)
                  except:
                      Exception
                  try:
                      chat_server.conn.sendall(text)
                  except:
                      Exception
                  time.sleep(0)
            def kill(self):
                self.running = 0

    # Prompt, object instantiation, and threads start here.

    ip_addr = raw_input('Type IP address or press enter: ')

    if ip_addr == '':
        chat_server = Chat_Server()
        chat_client = Chat_Client()
        chat_server.start()
        text_input = Text_Input()
        text_input.start()

    else:
        chat_server = Chat_Server()
        chat_client = Chat_Client()
        chat_client.host = ip_addr
        text_input = Text_Input()
        chat_client.start()
        text_input.start()

if __name__ == "__main__":
    main()

This script works absolutely fine across a home network, with 192.168... internal IP addresses.

On a school network, with 172... IP addresses, it doesn't seem to work. There is no connection error, but messages are not sent or received, with the exception of if there are two instances of the application being run on the same computer with the same internal IP address, in which case the program works flawlessly.

I am very new to sockets and this sort of networking, so I am wondering if anyone can point out to me why this is the case. Might it be the difference in IP addresses, for example?

Thank you in advance.

Answer 1

I see you're connecting on port 23647 - you may not have access to this on your school network. Check if this port has traffic enabled. see: Port Forwarding for details.

Something like: this site/tool may allow you to check quickly.