ZeroMQ的3种基本模式

    ZeroMQ只是一个库，要想在python中使用需要下载相应的模块python3-zmq，下面直接介绍它的3中基本的模式。

1.Request-Reply

server

import zmq
import time

context = zmq.Context()
socket = context.socket(zmq.REP)
socket.bind("tcp://*:5555")

while True:
    #  Wait for next request from client
    message = socket.recv()
    print("Received request: ", message.decode('utf-8'))

    time.sleep(1)  # Do some 'work'

    #  Send reply back to client
    socket.send_string("World")

client

import zmq
context = zmq.Context()

subscriber = context.socket(zmq.REQ)
subscriber.connect("tcp://localhost:5555")

for request in range(1, 10):
    print("Sending request ", request, "...")
    subscriber.send_string("Hello")

    #  Get the reply.
    message = subscriber.recv()
    print("Received reply ", request, "[", message.decode('utf-8'), "]")

• 服务端绑定端口，准守格式protocal://interface:port，protocal定义了数据传输时的协议，例中使用tcp协议（一般是tcp, udp，不能使用http，因为http是应用层的协议，socket位于应用层和运输层之间，应该使用socket下一层的协议），interface指ip地址，例中用 '*' 号代表了本机所有IP地址（多宿主主机有多个IP地址）
• 客户端连接服务器绑定的端口，用于和服务端之间相互传输数据，为什么服务端用bind, 客户端用connect，stackoverflow上有个回答做了很好的解释：https://stackoverflow.com/questions/27014955/socket-connect-vs-bind
• socket之间传递的是byte数据，接收到data后使用utf-8解码查看，发送字符串需使用send_string接口

2. Publish-Subscribe

server

# -*- coding=utf-8 -*-
import zmq
import time

context = zmq.Context()
socket = context.socket(zmq.PUB)
socket.bind("tcp://*:5555")

i = 1
while True:
    print('发送消息')
    socket.send_string("消息群发" + str(i))
    time.sleep(1)
    i += 1

client1      

# -*- coding=utf-8 -*-

import zmq

context = zmq.Context()
socket = context.socket(zmq.SUB)
socket.connect("tcp://localhost:5555")
socket.setsockopt_string(zmq.SUBSCRIBE, '')  # 消息过滤
while True:
    response = socket.recv()  # 消息发送是以bytes形式，接收后需要解码
    print("response: %s" % response.decode('utf-8'))

 client2

# -*- coding=utf-8 -*-

import zmq

context = zmq.Context()
socket = context.socket(zmq.SUB)
socket.connect("tcp://localhost:5555")
socket.setsockopt_string(zmq.SUBSCRIBE, '')
while True:
    response = socket.recv();
    print("response: %s" % response.decode('utf-8'))

• 服务端socket类型为zmq.PUB, 客户端为zmq.SUB。
• 服务端逻辑独立，无论有没有客户端订阅，都会按照自己的逻辑发送广播

3. Parallel Pipeline

 

server

# -*- coding=utf-8 -*-
import zmq
import time

context = zmq.Context()
socket = context.socket(zmq.PUSH)
socket.bind("tcp://*:5557")

i = 1
while True:
    socket.send_string("测试消息:" + str(i))
    print("已发送")
    time.sleep(1)
    i += 1

worker1

# -*- coding=utf-8 -*-

import zmq

context = zmq.Context()

recive = context.socket(zmq.PULL)
recive.connect('tcp://127.0.0.1:5557')

sender = context.socket(zmq.PUSH)
sender.bind('tcp://*:5558')

while True:
    data = recive.recv()
    print("正在转发..." + data.decode('utf-8'))
    sender.send(data)

worker2

# -*- coding=utf-8 -*-

import zmq

context = zmq.Context()

recive = context.socket(zmq.PULL)
recive.connect('tcp://127.0.0.1:5557')

sender = context.socket(zmq.PUSH)
sender.bind('tcp://*:5559')

while True:
    data = recive.recv()
    print("正在转发..." + data.decode('utf-8'))
    sender.send(data)

client1, client2, client3

# -*- coding=utf-8 -*-

import zmq
import sys

context = zmq.Context()
socket = context.socket(zmq.PULL)
socket.connect("tcp://127.0.0.1:5558")
socket.connect("tcp://127.0.0.1:5559")

while True:
    response = socket.recv()
    print("response: %s" % response.decode('utf-8'))

• worker1， worker2分摊由server发出的消息，然后再分摊给client1, client2, client3，Push/Pull 的特点是无论是 Push 端还是 Pull 端都可以做 server，bind 到某个地址等待对方访问。如果我们在 Push 端绑定地址，那么这是一个 Push server，对应的 Pull clients 可以 connect 到这个 Push server 往外拉数据；反之，如果我们建立一个 Pull server，对应的 Push clients 可以 connect 到这个 Pull server 往里压数据。例中，worker1, worker2作为server端的Pull client, client端的Push Server。Server端只能有一个，因为server需要bind socket，而客户端只需要connect到server的socket就行
• server socket send数据时如果没有client socket连接，那么send将会阻塞，直到有client socket连接上

文章参考：

https://segmentfault.com/a/1190000012010573#articleHeader3

https://zhuanlan.zhihu.com/p/22947038