Socket Programming Issue - Python

Question

Alright, I've spent about three hours fiddling with socket programming in Python trying to make a simple chat program. I've gotten the client to send text to the server and then, from then client, it repeats the message to it's self. However, I want the message to be sent to the server and then the server, not the client, re-send it to all client's connected. I'm having issues doing this. This is my code so far:

Server Side Code:

import SocketServer

    def handle(self):
        data = self.request[0].strip()
        socket = self.request[1]
        print "%s wrote:" % self.client_address[0]
        print data
        socket.sendto(data.upper(), self.client_address)


if __name__ == "__main__":
    HOST, PORT = "localhost", 25555
    server = SocketServer.UDPServer((HOST, PORT), MyUDPHandler)
    server.serve_forever()

Client Side Code:

import socket
import sys
global HOST
global PORT
HOST, PORT = "localhost", 25555
while 1 > 0:
     data = raw_input(">".join(sys.argv[1:]))

# SOCK_DGRAM is the socket type to use for UDP sockets
     sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

# As you can see, there is no connect() call; UDP has no connections.
# Instead, data is directly sent to the recipient via sendto().
     sock.sendto(data + "\n", (HOST, PORT))
     received = sock.recv(1024)

     print "Sent:     %s" % data
 print "Received: %s" % received

whitey04 · Accepted Answer · 2011-02-05 02:11:52Z

1

Right now your app is instantiating the MyUDPHandler class for each client connection. When the connection is opened you need to store that instance to a static array or queue. Then when the handle() call is made it can loop through all those sockets and send a copy of the data to each of them.

I'd checkout the python documentation; it basically does what your looking to: http://docs.python.org/library/socketserver.html#asynchronous-mixins

And what I'd change from that example (Don't just drop this in; it probably has glaring bugs!):

handlerList = []

class ...

    def handle(self):
        handlerList.append(self)
        while (1):
          data = self.request.recv(1024)
          if (not data):
            break
          cur_thread = threading.currentThread()
          response = "%s: %s" % (cur_thread.getName(), data)
          for x in handlerList:
            x.request.send(response)
        psudo_code_remove_self_from_handlerList()

edited Feb 5, 2011 at 2:11

answered Feb 5, 2011 at 1:53

whitey04

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4 Comments

Noah R Over a year ago

Is there a tutorial on doing this? If not, could you please provide an example?

whitey04 Over a year ago

Is your intention to open a new UDP connection for each line? Right now it looks like you renegotiate a new socket each time.

whitey04 Over a year ago

Using threads you can keep the same socket open to rx/tx the data back and forth. Without the thread mixin you have to handle a new UDP request each time as the handle() call is synchronous (can't handle a new one until the last one is done). This makes it difficult as I was trying to store the handler object so you can go through the list and send the data on each one.

Noah R Over a year ago

The code you gave me has a lot of errors.... could you revise it before I accept an answer... and thanks for the explanations...

Noctis Skytower · Accepted Answer · 2011-02-05 05:56:25Z

Would you like to play with a server that echos packets to all sockets but the original source of the data?

import socket, select

def main():
    server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    server.bind(('', 8989))
    server.listen(5)
    sockets = [server]
    while True:
        for sender in select.select(sockets, [], [])[0]:
            if sender is server:
                sockets.append(server.accept()[0])
            else:
                try:
                    message = sender.recv(4096)
                except socket.error:
                    message = None
                if message:
                    for receiver in sockets:
                        if receiver not in (server, sender):
                            receiver.sendall(message)
                else:
                    sender.shutdown(socket.SHUT_RDWR)
                    sender.close()
                    sockets.remove(sender)

if __name__ == '__main__':
    main()

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