Question

I create a new connection thread each time a connection with a client is made. However on the second time I run a client script, I get an error, how come?

The Client

from multiprocessing.connection import Client
conn = Client(('localhost', 5555), authkey='secret_password')
conn.send('Hello World!')
conn.close()

The Server

import time
from multiprocessing.connection import Listener
from threading import Thread

_threads = []
_listener = Listener(('localhost', 5555), authkey='secret_password')

def start_server_thread():
    global _threads
    _threads.append(Thread(target=threaded_server))
    _threads[-1].daemon = True
    _threads[-1].start()

def threaded_server():
    conn = _listener.accept()
    print str(conn.recv())
    conn.close()
    _listener.close()

if __name__ == "__main__":
    start_server_thread()
    while True:
        time.sleep(1)

The Error

Traceback (most recent call last):
  File "C:\dev\spyker\t2.py", line 3, in <module>
    conn = Client(('localhost', 5555), authkey='secret_password')
  File "C:\Python26\lib\multiprocessing\connection.py", line 143, in Client
    c = SocketClient(address)
  File "C:\Python26\lib\multiprocessing\connection.py", line 263, in SocketClient
    s.connect(address)
  File "<string>", line 1, in connect
socket.error: [Errno 10061] No connection could be made because the target machine actively refused it

Answer 1

You have a few problems with this server code.

You are closing the listener after the first connection

You arent looping for more connections

import time
from multiprocessing.connection import Listener
from threading import Thread

_threads = []

def start_server_thread():
    global _threads
    _threads.append(Thread(target=threaded_server))
    _threads[-1].daemon = True
    _threads[-1].start()

def threaded_server():
    while True:
        conn = _listener.accept()
        print str(conn.recv())
        conn.close()


if __name__ == "__main__":
    _listener = Listener(('localhost', 5555), authkey='secret_password')

    start_server_thread()
    while True:
        time.sleep(1)

    _listener.close()

Disclaimer: I think is is kind of a messy way to write the server. I am only posting a fix for your current code 🙂

Here is a slightly cleaned up version of your same code. Still not 100% ideal but cleaner I think?

import time
from multiprocessing.connection import Listener
from threading import Thread

class Server(Listener):

    def __init__(self, *args, **kwargs):
        super(Server, self).__init__(*args, **kwargs)
        self._thread = None
        self._stopping = False


    def serve(self):
        self._stopping = False
        self._thread = Thread(target=self._serve)
        self._thread.daemon = True
        self._thread.start()

    def _serve(self):
        threads = []
        while not self._stopping:
            conn = self.accept()
            t = Thread(target=self.handleConnection, args=(conn,))
            t.start()
            threads.append(t)


    def stop(self):
        if not self._stopping:
            print "Stopping."
            self._stopping = True
            self._thread.join(3)
            self.close()  

    def handleConnection(self, conn):
        print str(conn.recv())
        conn.close()        


if __name__ == "__main__":
    listener = Server(('localhost', 5555), authkey='secret_password')
    listener.serve()

    try:
        while True:
            time.sleep(1)
    except KeyboardInterrupt, e:
        listener.stop()