Thread UDP Socket

Question

I'm trying to make a multi threading udp server with python.

Here is what I am doing :

#!/usr/bin/python
# -*- coding:Utf-8 -*-

import sys
import socket
from thread import start_new_thread


class Broker():
    def __init__(self, ip, port):
        self.s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
        self.s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        self.ip = ip
        self.port = port
        self.s.bind((ip, port))
        self.listclients = []

def listenMod(b):
    dic = {}
    msg, ip = b.s.recvfrom(1024)
    dic[msg] = ip
    b.listclients.append(dic)
    print msg, " is connected."


def broker(arg):
    try:
        b = Broker(arg[2], int(arg[3]))
        start_new_thread(listenMod, (b, ))

    except Exception, e:
        print e
        sys.exit(-1)


def client(arg):
    try:
        pass
    except:
        pass

def usage():
    print "usage ./udps.py <-b|-c> <args>"
    print "-b\tserver mode\n\t<args>: host port"
    sys.exit()

def main():
    i = 1
    if len(sys.argv) > 1:
        while i < len(sys.argv):
            if sys.argv[1] == "-b":
                broker(sys.argv)
            elif sys.argv[1] == "-c":
                pass
            else:
                usage()
    else:
        usage()



if __name__ == '__main__':
    main()

It always prints "[Errno 48] Address already in use"

I'm using this because I would like to be able do to some special things with my clients but also be able to connect new clients at the same time.

Do you call `broker()` multiple times? You can't bind a socket to one single port multiple times… Maybe you show some more code, related to the usage of `broker()`. — tamasgal, Dec 19 '14 at 09:02
no i don't. Actually it works if i don't use : start_new_thread(listenMod, (b, )) but just : listenMod(b) — ZeenaZeek, Dec 19 '14 at 09:04
Which line of your code fails? Can you provide a full working example program? — John Zwinck, Dec 19 '14 at 09:04
You have to show how this class is being used. You can't bind to the same port number twice - only one socket can be bound to a port. — ErikR, Dec 19 '14 at 09:04
start_new_thread(listenMod, (b, )) makes my code failed. I call my class constructor once. — ZeenaZeek, Dec 19 '14 at 09:05
Actually it's not my own function [link]https://docs.python.org/2/library/thread.html — ZeenaZeek, Dec 19 '14 at 09:07
not at all. It works if I replace `start_new_thread(listenMod, (b, )` by `listenMod(b)` — ZeenaZeek, Dec 19 '14 at 09:10
Just provide a working reproducible example, which everyone can launch. — tamasgal, Dec 19 '14 at 09:12
`broker(sys.argv)` is not a working example… There are imports missing and syntax errors in your code. — tamasgal, Dec 19 '14 at 09:16
This question will be flagged if the OP fails to provide a working example that can reproduce the problem. — ρss, Dec 19 '14 at 09:23

score 0 · Accepted Answer · edited May 23 '17 at 12:12

0

First, don't use SO_REUSEADDR. There are legitimate uses of SO_REUSEADDR, but in most simple cases it is not useful, and it hides the real problem. Feel free to re-add it if needed, but only when your program works without it.

Your problem here is in your main. You are looping on the number of arguments, but never increment i, so it loops infinitely. Also you are always testing argv[1]. If there are 4 arguments, and the 2nd is '-b', you will call broker() 4 times, which will obviously not work. Also, note that if your loop ends and the main exit, your program will terminate immediately, so you should at least add a while(True): sleep(5) at the end, but it's not a solution.

edited May 23 '17 at 12:12

Community

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answered Dec 19 '14 at 10:38

ElderBug

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Thanks for your answer. I use SO_REUSEADDR cause my code is designed to make an UDP Hole Punching prototype. – ZeenaZeek Jan 30 '15 at 13:55
@ZeenaZeek Hole punching doesn't require SO_REUSEADDR. But well, if you need it for your implementation it's not a problem. SO_REUSEADDR isn't bad in itself, just keep in mind that it can hide potential problems. – ElderBug Jan 30 '15 at 14:18

Thread UDP Socket

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