How to coreclty solve ZMQ socket error “zmq.error.ZMQError: Address in use” in python

Question

I am using a windows 7 machine with Python 2.7 to make a simple Client/Server ZMQ proof of concept. I ran into this scenario where the listening socket(Server side of the app) is already in use and this throws "zmq.error.ZMQError: Address in use" error.
How do you think is the best way to avoid this error? I was thinking of, when binding the socket catch this error and if error is thrown restart the context and the socket. This is not working, is still throws and error when binding. Server code:

class ZMQServer:
    context = None
    socket = None

    def __init__(self, port):
        self.context = zmq.Context()
        self.socket = self.context.socket(zmq.REP)
        try:
            self.socket.bind("tcp://*:"+str(port))
        except zmq.error.ZMQError:
            print ("socket already in use, restarting")
            self.socket.close()
            self.context.destroy()
            self.context = zmq.Context()
            self.socket = self.context.socket(zmq.REP)
            self.socket.bind("tcp://*:"+str(port))

Answer 1

I tried another approach, instead of checking the availability of the socket, I am trying to manage it correclty, to do this:

• Created the listener async, on a separate thread.
• Created a method that will close the socket at exit

• In the socket binding I only catch the ZMQError and display it, I didn;t find a way to fix the blocked socked there.
  

• The recv method that receives the messages is NON-blocking

So, the code now looks like this:

"

import time
import zmq
import threading

class ZMQServer:
context = None
socket = None
alive = False
ZMQthread = None
def __init__(self, port):
    self.context = zmq.Context()
    self.socket = self.context.socket(zmq.REP)
    try:
        self.socket.bind("tcp://*:"+str(port))
    except zmq.error.ZMQError:
        print ("socket already in use, try restarting it")
        self.alive = False
    self.alive = True

def StartAsync(self):
    self.alive = True
    ZMQthread = threading.Thread(target=self.Start)
    ZMQthread.start()

def Start(self):
    while self.alive == True:
        #  Wait for next request from client
        print("Wait for next request from client")
        try: 
            message = self.socket.recv(zmq.NOBLOCK)
            print("Received request: %s" % message)
            #  Do some 'work'
            time.sleep(1)
            #  Send reply back to client
            self.socket.send(b"World")    
        except: 
            print "no message received in time. trying again"

def CloseServer(self):
    print("Stoping the server")
    self.alive = False
    if(self.socket.closed == False):
        self.socket.close()
    if self.ZMQthread and self.ZMQthread.is_alive() == True:
        self.ZMQthread.join()

if __name__ == '__main__':
    zmqServer = ZMQServer(5555)
    zmqServer.StartAsync()
    time.sleep(20)
    zmqServer.CloseServer()