pyzmq - Example message loss

import zmq
import threading
import time

context = zmq.Context()



def BThread():
    sb = context.socket(zmq.ROUTER)
    sb.setsockopt(zmq.IDENTITY, b"B")
    sb.connect("tcp://127.0.0.1:43289")
    for index in range(1000):
        sb.send_multipart([b"A", b"Message"])

if __name__ == '__main__':
    sa = context.socket(zmq.ROUTER)
    sa.setsockopt(zmq.IDENTITY, b"A")
    sa.bind("tcp://127.0.0.1:43289")
    bt = threading.Thread(target=BThread)
    bt.start()
    nbMsg = 0
    for index in range(1000):
        msg = sa.recv()
        nbMsg += 1
        print(nbMsg)
    bt.join()