Deepal Deepal - 5 months ago 12x
Python Question

Multi Threaded TCP server in Python

I have created a simple multi threaded tcp server using python's threding module. This server creates a new thread each time a new client is connected.

#!/usr/bin/env python

import socket, threading

class ClientThread(threading.Thread):

def __init__(self,ip,port):
self.ip = ip
self.port = port
print "[+] New thread started for "+ip+":"+str(port)

def run(self):
print "Connection from : "+ip+":"+str(port)

clientsock.send("\nWelcome to the server\n\n")

data = "dummydata"

while len(data):
data = clientsock.recv(2048)
print "Client sent : "+data
clientsock.send("You sent me : "+data)

print "Client disconnected..."

host = ""
port = 9999

tcpsock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
tcpsock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

threads = []

while True:
print "\nListening for incoming connections..."
(clientsock, (ip, port)) = tcpsock.accept()
newthread = ClientThread(ip, port)

for t in threads:

Then I opened two new terminals and connected to the server using netcat. Then, when I type and send my first data to the server using the first terminal I connected, reply from the server comes to the other terminal and first connection got disconnected. I guessed the reason but I am doubtful whether this happens because clientsock variable is overwritten so that it refers to the second connection's socket. Am I correct and then how to avoid that?

Is there a way other than using an array with limited number of socket variables and using each variable for each connection?


You should pass the client sock to the thread like you do with the ip address and the port:

class ClientThread(threading.Thread):

    def __init__(self, ip, port, socket):
        self.ip = ip
        self.port = port
        self.socket = socket
        print "[+] New thread started for "+ip+":"+str(port)

    def run(self):
        # use self.socket to send/receive

(clientsock, (ip, port)) = tcpsock.accept()
newthread = ClientThread(ip, port, clientsock)