Question

这是我的剧本。


#!/usr/bin/env python

import traceback
import sys
import zmq
from time import sleep

print "Creating the zmq.Context"
context = zmq.Context()

print "Binding the publisher to the local socket at port 5557"
sender = context.socket(zmq.PUB)
sender.bind("tcp://*:5557")

print "Binding the subscriber to the local socket at port 5557"
receiver = context.socket(zmq.SUB)
receiver.connect("tcp://*:5557")

print "Setting the subscriber option to get only those originating from \"B\""
receiver.setsockopt(zmq.SUBSCRIBE, "B")

print "Waiting a second for the socket to be created."
sleep(1)

print "Sending messages"
for i in range(1,10):
    msg = "msg %d" % (i)
    env = None
    if i % 2 == 0:
        env = ["B", msg]
    else:
        env = ["A", msg]
    print "Sending Message:  ", env
    sender.send_multipart(env)

print "Closing the sender."
sender.close()

failed_attempts = 0
while failed_attempts < 3:
    try:
        print str(receiver.recv_multipart(zmq.NOBLOCK))
    except:
        print traceback.format_exception(*sys.exc_info())
        failed_attempts += 1 

print "Closing the receiver."
receiver.close()

print "Terminating the context."
context.term()

"""
Output:

Creating the zmq.Context
Binding the publisher to the local socket at port 5557
Binding the subscriber to the local socket at port 5557
Setting the subscriber option to get only those originating from "B"
Waiting a second for the socket to be created.
Sending messages
Sending Message:   ['A', 'msg 1']
Sending Message:   ['B', 'msg 2']
Sending Message:   ['A', 'msg 3']
Sending Message:   ['B', 'msg 4']
Sending Message:   ['A', 'msg 5']
Sending Message:   ['B', 'msg 6']
Sending Message:   ['A', 'msg 7']
Sending Message:   ['B', 'msg 8']
Sending Message:   ['A', 'msg 9']
Closing the sender.
['B', 'msg 2']
['B', 'msg 4']
['B', 'msg 6']
['B', 'msg 8']
['Traceback (most recent call last):\n', '  File "./test.py", line 43, in \n    print str(receiver.recv_multipart(zmq.NOBLOCK))\n', '  File "socket.pyx", line 611, in zmq.core.socket.Socket.recv_multipart (zmq/core/socket.c:5181)\n', '  File "socket.pyx", line 514, in zmq.core.socket.Socket.recv (zmq/core/socket.c:4811)\n', '  File "socket.pyx", line 548, in zmq.core.socket.Socket.recv (zmq/core/socket.c:4673)\n', '  File "socket.pyx", line 99, in zmq.core.socket._recv_copy (zmq/core/socket.c:1344)\n', 'ZMQError: Resource temporarily unavailable\n']
['Traceback (most recent call last):\n', '  File "./test.py", line 43, in \n    print str(receiver.recv_multipart(zmq.NOBLOCK))\n', '  File "socket.pyx", line 611, in zmq.core.socket.Socket.recv_multipart (zmq/core/socket.c:5181)\n', '  File "socket.pyx", line 514, in zmq.core.socket.Socket.recv (zmq/core/socket.c:4811)\n', '  File "socket.pyx", line 548, in zmq.core.socket.Socket.recv (zmq/core/socket.c:4673)\n', '  File "socket.pyx", line 99, in zmq.core.socket._recv_copy (zmq/core/socket.c:1344)\n', 'ZMQError: Resource temporarily unavailable\n']
['Traceback (most recent call last):\n', '  File "./test.py", line 43, in \n    print str(receiver.recv_multipart(zmq.NOBLOCK))\n', '  File "socket.pyx", line 611, in zmq.core.socket.Socket.recv_multipart (zmq/core/socket.c:5181)\n', '  File "socket.pyx", line 514, in zmq.core.socket.Socket.recv (zmq/core/socket.c:4811)\n', '  File "socket.pyx", line 548, in zmq.core.socket.Socket.recv (zmq/core/socket.c:4673)\n', '  File "socket.pyx", line 99, in zmq.core.socket._recv_copy (zmq/core/socket.c:1344)\n', 'ZMQError: Resource temporarily unavailable\n']
Closing the receiver.
Terminating the context.
"""

而且，问题是......为什么这段代码不起作用？

[编辑]在zeromq邮件列表上获得超快速响应后，我更新了上面的代码。

Answer 1

Credit：Chuck Remes

您可能需要在套接字创建步骤（bind，connect，setsockopt）和消息的实际传输之间进行“休眠”。绑定＆amp;连接操作是异步的，因此在到达发送所有消息的逻辑时它们可能无法完成。在这种情况下，通过PUB套接字发送的任何消息都将被删除，因为zmq_bind（）操作在另一个套接字成功连接到它之前不会创建队列。

作为旁注，在此示例中您不需要创建2个上下文。两个套接字都可以在同一个上下文中创建。它没有伤害，但也没有必要。

信用：彼得

Ch1末尾有一个“问题解决者”解释了这一点。

某些套接字类型（ROUTER和PUB）将以静默方式丢弃消息   他们没有收件人。正如查克所说，连接正如   异步，大约需要100毫秒。如果你启动两个线程，绑定   一方面，连接另一方，然后立即开始发送数据   通过这种套接字类型，您将丢失前100毫秒的数据   （大约）。

睡觉是一种残酷的“证明它有效”的选择。现实   你会以某种方式同步，或者（更典型地）期望消息丢失   作为正常启动的一部分（即将发布的数据视为纯粹的   广播没有明确的开始或结束）。

有关详细信息，请参阅天气更新示例，syncpub和syncsub。

Answer 2

死灵张贴，但是对于那些对除睡觉以外的解决方案感兴趣的人，有显示器。

您可以设置监视器回调并在ZMQ_EVENT_CONNECTED事件上调用。

在http://api.zeromq.org/3-3:zmq-ctx-set-monitor上查看详细信息和示例。

零mq pub / sub，multipart不工作

2 个答案: