Question

I am trying to make multiprocessing and socket programming work together, but, I am stuck at this point. Problem is that, I am getting this error:

  File "multiprocesssockserv.py", line 11, in worker
    clientsocket = socket.fromfd(clientfileno, socket.AF_INET, socket.SOCK_STREAM)
error: [Errno 9] Bad file descriptor

Complete code that causing the error is as following:

import multiprocessing as mp
import logging
import socket

logger = mp.log_to_stderr(logging.WARN)

def worker(queue):
    while True:
        clientfileno = queue.get()
        print clientfileno
        clientsocket = socket.fromfd(clientfileno, socket.AF_INET, socket.SOCK_STREAM)
        clientsocket.recv()
        clientsocket.send("Hello World")
        clientsocket.close()

if __name__ == '__main__':
    num_workers = 5
    socket_queue = mp.Queue()
    workers = [mp.Process(target=worker, args=(socket_queue,)) for i in
            range(num_workers)]

    for p in workers:
        p.daemon = True
        p.start()

    serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    serversocket.bind(('',9090))
    serversocket.listen(5)
    while True:
        client, address = serversocket.accept()
        socket_queue.put(client.fileno())

edit: I am using socket.fromfd because I can’t put sockets into a queue 🙂 I need a way to access same sockets from different processes somehow. That is the core of my problem.

Answer 1

After working on this for a while, I decided to approach this problem from a different angle, and following method seems to be working for me.

import multiprocessing as mp
import logging
import socket
import time

logger = mp.log_to_stderr(logging.DEBUG)

def worker(socket):
    while True:
        client, address = socket.accept()
        logger.debug("{u} connected".format(u=address))
        client.send("OK")
        client.close()
if __name__ == '__main__':
    num_workers = 5

    serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    serversocket.bind(('',9090))
    serversocket.listen(5)

    workers = [mp.Process(target=worker, args=(serversocket,)) for i in
            range(num_workers)]

    for p in workers:
        p.daemon = True
        p.start()

    while True:
        try:
            time.sleep(10)
        except:
            break