Accepting multiple clients in python socket server

Question

I'm trying to build a simple socket server in python:

import socket
import threading
import time
def handle(conn_addr):
 print("Someone Connected")
 time.sleep(4)
 print("And now I die")
host = ''
port = 5000
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
try:
 s.bind((host,port))
except socket.error as e:
 print(str(e))
s.listen(2)
while True:
 threading.Thread(handle(s.accept())).start()
print("Should never be reached")

The socket server should accept multiple clients at the same time. I tried to test its functionality by calling telnet localhost 5000 from multiple tabs from my shell however the pattern that i get is

Someone Connected
And now I die
Someone Connected
And now I die

Instead of

Someone Connected
Someone Connected
Someone Connected

I call the telnet command within 4 seconds of each other so it should have 2 messages of connected in a row however the message is only returned after the previous socket is disconnected. Why is that and how could I go round fixing this?

• OneCricketeer: You are printing the die statement without closing the socket. The clients should still be connected
• Bula: But why doesn't the function print "someone connected" as soon as I connect to it? It always waits for "die" to be printed ?
• OneCricketeer: As far as I can tell, it should print "connected", then pause for 4 seconds, then print "die" (even though you don't close the socket). Is that not what is happening?

Answer 1

Its a classic mistake. You called handle() (which slept for 4 seconds) and then tried to create a thread from its result. The target should be a function reference and args should be passed separately.

threading.Thread(target=handle, args=(s.accept(),)).start()

In this version, the main thread waits for an accept and then creates the thread that runs handle.

• Arsalan Saleem: This helped us in creating a delegation for the event socket.recv(1024) in python, @tdelaney, would you like to give feedback on that ? thanks.
• tdelaney: @ArsalanSaleem - I'm not sure how that would work. Thread(target=mysock.rec, args=(1024,)).start() would be problematic. Where would the received data go to? recv may get anything from 0 to 1024 bytes (socket closed is 0, or since its byte oriented, only a partial message) and could get an Exception. I'd need the details to know. .... and that would be hard to put in a comment here. Perhaps a new question or maybe something on codereview.stackexchange.com?