python zeromq

python examples https://github.com/imatix/zguide/tree/master/examples/Python

hwserver.py

#
# Hello World server in Python
# Binds REP socket to tcp://*:5555
# Expects "Hello" from client, replies with "World"
#
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

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

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

#
#   Hello World server in Python
#   Binds REP socket to tcp://*:5555
#   Expects "Hello" from client, replies with "World"
#
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

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

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

hwclient.py

#
# Hello World client in Python
# Connects REQ socket to tcp://localhost:5555
# Sends "Hello" to server, expects "World" back
#
import zmq

context = zmq.Context()

# Socket to talk to server
print "Connecting to hello world server..."
socket = context.socket(zmq.REQ)
socket.connect ("tcp://localhost:5555")

# Do 10 requests, waiting each time for a response
for request in range (1,10):
print "Sending request ", request,"..."
socket.send ("Hello")

# Get the reply.
message = socket.recv()
print "Received reply ", request, "[", message, "]"

#
#   Hello World client in Python
#   Connects REQ socket to tcp://localhost:5555
#   Sends "Hello" to server, expects "World" back
#
import zmq

context = zmq.Context()

#  Socket to talk to server
print "Connecting to hello world server..."
socket = context.socket(zmq.REQ)
socket.connect ("tcp://localhost:5555")

#  Do 10 requests, waiting each time for a response
for request in range (1,10):
    print "Sending request ", request,"..."
    socket.send ("Hello")
    
    #  Get the reply.
    message = socket.recv()
    print "Received reply ", request, "[", message, "]"

问题3：zeroMQ实现一个消息层？

答：

实现一个ZeroMQ消息层需要三个步骤：

1.选择传输协议

0MQ提供了4种不同的传输协议

INPROC an In-Process communication model

IPC an Inter-Process communication model

MULTICAST multicast via PGM, possibly encapsulated in UDP

TCP a network based transport

2.建立基础

由于在网络中两个端点是相对动态的，很难有一个稳定的单一连接点。

如果是这种情况，可以使用由0MQ提供的转发设备。

转发设备可以绑定2个不同端口，并且转发消息从一个端点到另一个端点。

这样做的话，在网络中转发设备能够变成一个稳定的点，其它组件都可以去连接。

0MQ提供了3种类型的设备

QUEUE, a forwarder for the request/response messaging pattern

FORWARDER, a forwarder for the publish/subscribe messaging pattern

STREAMER, a forwarder for the pipelined messaging pattern

3.选择通讯模式

0MQ支持4种模式

REQUEST/REPLY, bidirectional, load balanced and state based

PUBLISH/SUBSCRIBE, publish to multiple recipients at once

UPSTREAM / DOWNSTREAM, distribute data to nodes arranged in a pipeline

PAIR, communication exclusively between peers

Req/Rep

均衡负载请求：

server 1

import zmq
context = zmq.Context()
socket = context.socket(zmq.REP)
socket.bind("tcp://127.0.0.1:5000")

while True:
msg = socket.recv()
print "Got", msg
socket.send(msg)

import zmq
context = zmq.Context()
socket = context.socket(zmq.REP)
socket.bind("tcp://127.0.0.1:5000")
 
while True:
    msg = socket.recv()
    print "Got", msg
    socket.send(msg)

server 2

import zmq
context = zmq.Context()
socket = context.socket(zmq.REP)
socket.bind("tcp://127.0.0.1:6000")

while True:
msg = socket.recv()
print "Got", msg
socket.send(msg)

import zmq
context = zmq.Context()
socket = context.socket(zmq.REP)
socket.bind("tcp://127.0.0.1:6000")
 
while True:
    msg = socket.recv()
    print "Got", msg
    socket.send(msg)

client

import zmq
context = zmq.Context()
socket = context.socket(zmq.REQ)
socket.connect("tcp://127.0.0.1:5000")
socket.connect("tcp://127.0.0.1:6000")

for i in range(10):
msg = "msg %s" % i
socket.send(msg)
print "Sending", msg
msg_in = socket.recv()

import zmq
context = zmq.Context()
socket = context.socket(zmq.REQ)
socket.connect("tcp://127.0.0.1:5000")
socket.connect("tcp://127.0.0.1:6000")
 
for i in range(10):
    msg = "msg %s" % i
    socket.send(msg)
    print "Sending", msg
    msg_in = socket.recv()

会发现client的请求会被均衡的分配给两个server

Example client output:

Sending msg 0
Sending msg 1
Sending msg 2
Sending msg 3
Sending msg 4
Sending msg 5
Sending msg 6
Sending msg 7
Sending msg 8
Sending msg 9

Example output server 1 at port 5000:

Got msg 0
Got msg 2
Got msg 4
Got msg 6
Got msg 8

Example output server 2 at port 6000:

Got msg 1
Got msg 3
Got msg 5
Got msg 7
Got msg 9

现在，如果我们要加入一个额外的server去管理我们的请求，我们将不得不修改我们的代码。

这是非常麻烦的，我们需要让每个client都知道有一个额外的server可以均衡请求。

为了解决这个问题，替代client直接去连接多个server的方式，client去连接转发设备，再由转发设备路由全部的消息给server。

Pub/Sub

在pub/sub模式下组件是松耦合的。类似于广播电台。

一个广播server为现场足球赛

import zmq
from random import choice
context = zmq.Context()
socket = context.socket(zmq.PUB)
socket.bind("tcp://127.0.0.1:5000")

countries = ['netherlands','brazil','germany','portugal']
events = ['yellow card', 'red card', 'goal', 'corner', 'foul']

while True:
msg = choice( countries ) +" "+ choice( events )
print "->",msg
socket.send( msg )<span style="white-space: normal;"> </span>

import zmq
from random import choice
context = zmq.Context()
socket = context.socket(zmq.PUB)
socket.bind("tcp://127.0.0.1:5000")
 
countries = ['netherlands','brazil','germany','portugal']
events = ['yellow card', 'red card', 'goal', 'corner', 'foul']
 
while True:
    msg = choice( countries ) +" "+ choice( events )
    print "->",msg
    socket.send( msg ) 

输出

-> portugal corner
-> portugal yellow card
-> portugal goal
-> netherlands yellow card
-> germany yellow card
-> brazil yellow card
-> portugal goal
-> germany corner
…

一个客户端去收听特定的消息

import zmq

context = zmq.Context()
socket = context.socket(zmq.SUB)
socket.connect("tcp://127.0.0.1:5000")
socket.setsockopt(zmq.SUBSCRIBE, "netherlands")
socket.setsockopt(zmq.SUBSCRIBE, "germany")

while True:
print socket.recv()

import zmq
 
context = zmq.Context()
socket = context.socket(zmq.SUB)
socket.connect("tcp://127.0.0.1:5000")
socket.setsockopt(zmq.SUBSCRIBE, "netherlands")
socket.setsockopt(zmq.SUBSCRIBE, "germany")
 
while True:
    print  socket.recv()

输出

netherlands red card
netherlands goal
netherlands red card
germany foul
netherlands yellow card
germany foul
netherlands goal
netherlands corner
germany foul
netherlands corner
…

Pipelining

并发处理数据，其工作模式

一个工作者得到来自上游socket的消息，一旦处理完成后发送消息到下游。

Paired socket

服务器监听某个端口，客户端连接到这个端口，消息可以双向流动。

server

import zmq
context = zmq.Context()
socket = context.socket(zmq.PAIR)
socket.bind("tcp://127.0.0.1:5555")

import zmq
context = zmq.Context()
socket = context.socket(zmq.PAIR)
socket.bind("tcp://127.0.0.1:5555")

client

import zmq
context = zmq.Context()
socket = context.socket(zmq.PAIR)
socket.connect("tcp://127.0.0.1:5555")

import zmq
context = zmq.Context()
socket = context.socket(zmq.PAIR)
socket.connect("tcp://127.0.0.1:5555")

ps:

推荐

http://www.zeromq.org/

http://nichol.as/zeromq-an-introduction