PyZMQ 中 ROUTER Socket 发消息给 REP Socket 失败！

我使用 ZeroMQ 实现了一个简单的请求-应答架构，其中使用了 ROUTER socket。在 PyZMQ 版本 2.1.11 中，这个架构工作正常。但当我在 PyZMQ 版本 14.0.0 上测试时，发送方 (REQ) 可以将消息发送给 ROUTER，而 ROUTER 也收到了消息并将其发送给了接收方 (REP)。然而，接收方却没有收到这条消息！我在将 PyZMQ 从版本 2.1.11 升级到 14.0.0 后遇到了这个问题。

网络拓扑图：

REQ <-> ROUTER <-> REP

代码示例：

sender.py

import zmq
import time

if __name__=='__main__':
    context = zmq.Context()
    socket = context.socket(zmq.REQ)
    socket.setsockopt(zmq.IDENTITY, "S")
    socket.connect("tcp://127.0.0.1:6660")
    i = 0
    while True:
        i += 1
        socket.send("R", zmq.SNDMORE)
        socket.send("", zmq.SNDMORE)
        socket.send("Message: %d" % i)
        print("Message : %d sent" % i)
        fromAddr = socket.recv()
        empty = socket.recv()
        resp = socket.recv()
        print("%s received!" % str(resp))
        time.sleep(1)

router.py

import zmq
import time

if __name__=='__main__':
    context = zmq.Context()
    frontend = context.socket(zmq.ROUTER)
    frontend.bind("tcp://*:6660")

    poll = zmq.Poller()
    poll.register(frontend, zmq.POLLIN)

    while True:
        sockets = dict(poll.poll(100))
        if frontend in sockets:
            if sockets[frontend] == zmq.POLLIN:
                fromAddr = frontend.recv()
                empty = frontend.recv()
                toAddr = frontend.recv()
                empty = frontend.recv()
                msg = frontend.recv()
                print("Message received from %s must be send to %s [%s]" % (str$
                frontend.send(toAddr, zmq.SNDMORE)
                frontend.send("", zmq.SNDMORE)
                frontend.send(fromAddr, zmq.SNDMORE)
                frontend.send("", zmq.SNDMORE)
                frontend.send(msg)
                print("Message has been send to %s!" % str(toAddr))

receiver.py

import zmq
import time

if __name__=='__main__':
    context = zmq.Context()
    socket = context.socket(zmq.REP)
    socket.setsockopt(zmq.IDENTITY, "R")
    socket.connect("tcp://127.0.0.1:6660")
    while True:
        print("Wating for request...")
        toAddr = socket.recv()
        empty = socket.recv()
        req = socket.recv()
        print("%s received!" % str(req))
        socket.send(toAddr, zmq.SNDMORE)
        socket.send(empty, zmq.SNDMORE)
        socket.send("Reply to %s" % str(req))

解决方案

根据 @nos 的说法，ROUTER 到 REP 的连接是无效的，但 ROUTER 到 ROUTER 的连接是有效的。因此，我只需将 REP socket 更改为 ROUTER 即可。

修改后的代码示例：

receiver.py

import zmq

if __name__=='__main__':
    context = zmq.Context()
    socket = context.socket(zmq.ROUTER)       # Changed
    socket.setsockopt(zmq.IDENTITY, "R1")
    socket.connect("tcp://127.0.0.1:6660")
    while True:
        print("Wating for request...")

        me = socket.recv()       # New
        empty = socket.recv()    # New
        toAddr = socket.recv()
        empty = socket.recv()
        req = socket.recv()
        print("%s received!" % str(req))

        socket.send(me, zmq.SNDMORE)       # New
        socket.send(empty, zmq.SNDMORE)    # New
        socket.send(toAddr, zmq.SNDMORE)
        socket.send(empty, zmq.SNDMORE)
        socket.send("Reply to %s" % str(req))

通过这个简单的修改，现在我可以成功地使用 ZeroMQ ROUTER socket 将消息发送给 REP socket 了。