ZMQ – Records And Memorys

November 28, 2018November 28, 2018

how python work as ZMP client

first install ZMQ , how to install see “python note “

注意在中文机器不能用这个命令 ; pip install pyzmq

因为有解码问题

how to make a hello world in python :

https://learning-0mq-with-pyzmq.readthedocs.io/en/latest/pyzmq/basics.html#installation

先启动 c++ 的 ZMQ server , 然后运行这个脚本

import zmq
import sys

context = zmq.Context()
print ("Connecting to server...")
socket = context.socket(zmq.REQ)
socket.connect ("tcp://localhost:5555")

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

import zmq

import sys

context = zmq.Context()

print ("Connecting to server...")

socket = context.socket(zmq.REQ)

socket.connect ("tcp://localhost:5555")

# Do 10 requests, waiting each time for a response

#for request in range (10):

socket.send_string("Hello")

# Get the reply.

message = socket.recv()

print(message)

#print ("Received reply ", request, "[", message, "]")

以上只是传string，怎么传 json

https://stackoverflow.com/questions/37765847/send-json-object-through-zmq-with-c-client-python-server

https://pyzmq.readthedocs.io/en/latest/serialization.html

- 没必要一定传json ，对于复杂的msg, 可以传递用空格分隔字符串，比如

这样的字符串：aa bb cc dd ee ff gg hh …. 也足够用了

改造后的python client 如下：

import zmq
import sys

context = zmq.Context()
print ("Connecting to server...")
socket = context.socket(zmq.REQ)
socket.connect ("tcp://localhost:5555")

#  Do 10 requests, waiting each time for a response
#for request in range (10):
socket.send_string("rb buy 3670")
print ("done send msg")
    #  Get the reply.
message = socket.recv()
print(message)
    #print ("Received reply ", request, "[", message, "]")

import zmq

import sys

context = zmq.Context()

print ("Connecting to server...")

socket = context.socket(zmq.REQ)

socket.connect ("tcp://localhost:5555")

# Do 10 requests, waiting each time for a response

#for request in range (10):

socket.send_string("rb buy 3670")

print ("done send msg")

# Get the reply.

message = socket.recv()

print(message)

#print ("Received reply ", request, "[", message, "]")

c++ server code :

#include "C:\\Program Files (x86)\\ZeroMQ 2.2.0\\include\\zmq.hpp"
#include <string>
#include <iostream>
#ifndef _WIN32
#include <unistd.h>
#else
#include <windows.h>
#include <vector>
#include <iostream>     // std::cout
#include <sstream>

#define sleep(n)    Sleep(n)
#endif

void dosth(const char* c1,const char* c2)
{
	if(strcmp (c2,"buy")==0)
		return;
	if(strcmp (c2,"sell")==0)
		return;

	return;


}

int main () {

    //  Prepare our context and socket
    zmq::context_t context (1);
    zmq::socket_t socket (context, ZMQ_REP);
    socket.bind ("tcp://*:5555");

    while (true) {
        zmq::message_t request;

        //  Wait for next request from client
        socket.recv (&request);
        //std::cout << "Received Hello" << std::endl;

		std::string rpl = std::string(static_cast<char*>(request.data()), request.size());

		std::cout << rpl << std::endl;

		std::istringstream iss(rpl);
		std::vector<std::string> results((std::istream_iterator<std::string>(iss)),
									 std::istream_iterator<std::string>());

		int i = atoi(results[2].c_str());
		dosth(results[0].c_str(),results[1].c_str());


        //  Do some 'work'
        sleep(1);

        //  Send reply back to client
        zmq::message_t reply (5);
        memcpy (reply.data (), "World", 5);
        socket.send (reply);
    }
    return 0;
}

#include "C:\\Program Files (x86)\\ZeroMQ 2.2.0\\include\\zmq.hpp"

#include <string>

#include <iostream>

#ifndef _WIN32

#include <unistd.h>

#else

#include <windows.h>

#include <vector>

#include <iostream> // std::cout

#include <sstream>

#define sleep(n) Sleep(n)

#endif

void dosth(const char* c1,const char* c2)

{

if(strcmp (c2,"buy")==0)

return;

if(strcmp (c2,"sell")==0)

return;

}

int main () {

// Prepare our context and socket

zmq::context_t context (1);

zmq::socket_t socket (context, ZMQ_REP);

socket.bind ("tcp://*:5555");

while (true) {

zmq::message_t request;

// Wait for next request from client

socket.recv (&request);

//std::cout << "Received Hello" << std::endl;

std::string rpl = std::string(static_cast<char*>(request.data()), request.size());

std::cout << rpl << std::endl;

std::istringstream iss(rpl);

std::vector<std::string> results((std::istream_iterator<std::string>(iss)),

std::istream_iterator<std::string>());

int i = atoi(results[2].c_str());

dosth(results[0].c_str(),results[1].c_str());

// Do some 'work'

sleep(1);

// Send reply back to client

zmq::message_t reply (5);

memcpy (reply.data (), "World", 5);

socket.send (reply);

}

return 0;

}

其中 split string 功能代码来自于：

https://www.fluentcpp.com/2017/04/21/how-to-split-a-string-in-c/

如何取出 message_t 里面的string 来自：

https://stackoverflow.com/questions/10901240/zeromq-how-to-access-tcp-message-in-c

PS : very important , after python client send , can not skip

message = socket.recv()
print(message)

1 2	message = socket.recv() print(message)

because send and recv must be pair

November 28, 2018

c++ create ZMQ client and server

in this site http://zeromq.org/distro:microsoft-windows

download Stable Release 2.2.0 win32 version

install on windows PC
in visual studio , create win32 console app , for server side ,use code

#include "C:\\Program Files (x86)\\ZeroMQ 2.2.0\\include\\zmq.hpp"
#include <string>
#include <iostream>
#ifndef _WIN32
#include <unistd.h>
#else
#include <windows.h>

#define sleep(n)    Sleep(n)
#endif

int main () {
    //  Prepare our context and socket
    zmq::context_t context (1);
    zmq::socket_t socket (context, ZMQ_REP);
    socket.bind ("tcp://*:5555");

    while (true) {
        zmq::message_t request;

        //  Wait for next request from client
        socket.recv (&request);
        std::cout << "Received Hello" << std::endl;

        //  Do some 'work'
        sleep(1);

        //  Send reply back to client
        zmq::message_t reply (5);
        memcpy (reply.data (), "World", 5);
        socket.send (reply);
    }
    return 0;
}

#include "C:\\Program Files (x86)\\ZeroMQ 2.2.0\\include\\zmq.hpp"

#include <string>

#include <iostream>

#ifndef _WIN32

#include <unistd.h>

#else

#include <windows.h>

#define sleep(n) Sleep(n)

#endif

int main () {

// Prepare our context and socket

zmq::context_t context (1);

zmq::socket_t socket (context, ZMQ_REP);

socket.bind ("tcp://*:5555");

while (true) {

zmq::message_t request;

// Wait for next request from client

socket.recv (&request);

std::cout << "Received Hello" << std::endl;

// Do some 'work'

sleep(1);

// Send reply back to client

zmq::message_t reply (5);

memcpy (reply.data (), "World", 5);

socket.send (reply);

}

return 0;

}

and for client side , use code :

//
//  Hello World client in C++
//  Connects REQ socket to tcp://localhost:5555
//  Sends "Hello" to server, expects "World" back
//
#include "C:\\Program Files (x86)\\ZeroMQ 2.2.0\\include\\zmq.hpp"
#include <string>
#include <iostream>

int main ()
{
    //  Prepare our context and socket
    zmq::context_t context (1);
    zmq::socket_t socket (context, ZMQ_REQ);

    std::cout << "Connecting to hello world server…" << std::endl;
    socket.connect ("tcp://localhost:5555");

    //  Do 10 requests, waiting each time for a response
    for (int request_nbr = 0; request_nbr != 10; request_nbr++) {
        zmq::message_t request (5);
        memcpy (request.data (), "Hello", 5);
        std::cout << "Sending Hello " << request_nbr << "…" << std::endl;
        socket.send (request);

        //  Get the reply.
        zmq::message_t reply;
        socket.recv (&reply);
        std::cout << "Received World " << request_nbr << std::endl;
    }
    return 0;
}

// Hello World client in C++

// Connects REQ socket to tcp://localhost:5555

// Sends "Hello" to server, expects "World" back

#include "C:\\Program Files (x86)\\ZeroMQ 2.2.0\\include\\zmq.hpp"

#include <string>

#include <iostream>

int main ()

{

// Prepare our context and socket

zmq::context_t context (1);

zmq::socket_t socket (context, ZMQ_REQ);

std::cout << "Connecting to hello world server…" << std::endl;

socket.connect ("tcp://localhost:5555");

// Do 10 requests, waiting each time for a response

for (int request_nbr = 0; request_nbr != 10; request_nbr++) {

zmq::message_t request (5);

memcpy (request.data (), "Hello", 5);

std::cout << "Sending Hello " << request_nbr << "…" << std::endl;

socket.send (request);

// Get the reply.

zmq::message_t reply;

socket.recv (&reply);

std::cout << "Received World " << request_nbr << std::endl;

}

return 0;

}

copy libzmq-v100-mt.lib and libzmq-v100-mt.dll to source.cpp folder

in linker—–>input , add libzmq-v100-mt.lib

compile and run .

September 28, 2018September 28, 2018

ZMQ 各种 socket 介绍

- router – dealer 模式

为什么有 router – dealer 模式 ? 处理多client , 多service 的情况

例如下图：

1个client,多个service , 最简单的设计方法是： connect each client socket to multiple service endpoints

在这种情况下：

One client socket can connect to multiple service sockets, and the REQ socket will then distribute requests among these services. Let’s say you connect a client socket to three service endpoints; A, B, and C. The client makes requests R1, R2, R3, R4. R1 and R4 go to service A, R2 goes to B, and R3 goes to service C.

This design lets you add more clients cheaply. You can also add more services. Each client will distribute its requests to the services. But each client has to know the service topology. If you have 100 clients and then you decide to add three more services, you need to reconfigure and restart 100 clients in order for the clients to know about the three new services.

不好的地方是： client必须知道所有的service ，当新增若干个service，每一个client 都要修改并重启

router 或者 dealer 就是在client 和 service 之间的中间层 , 用 zmq_poll() 实现： What we want is something sitting in between clients and services that centralizes all knowledge of the topology. Ideally, we should be able to add and remove services or clients at any time without touching any other part of the topology.

实现示例图是这样的：

In this simple extended request-reply pattern, REQ talks to ROUTER and DEALER talks to REP.

来源文档：

http://zguide.zeromq.org/page:all