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I want to implement a pub-sub infrastructure for our distributed system. The idea behind the network, which you can see in the picture is, that I want to implement publisher and subscriber in java. But in JZmq curve encryption is not yet supported. So I wanna implement the proxies in C(++) where it is available.(at the moment I have it just in java)

here's my code

Subscriber.java :

import java.nio.charset.Charset;

import org.zeromq.ZMQ;
import org.zeromq.ZMQ.Context;
import org.zeromq.ZMQ.Socket;

public class Subscriber {
    public static void main(String[] args) {
        String address = args[0];
        String topic = args[1];

        Context context = ZMQ.context(1);
        Socket subscriber = context.socket(ZMQ.SUB);
        subscriber.connect(address);
        subscriber.subscribe(topic.getBytes());

        while (!Thread.currentThread().isInterrupted()) {
            String top = subscriber.recvStr(Charset.defaultCharset());
            String contents = subscriber.recvStr(Charset.defaultCharset());

            System.out.println(top + ": " + contents);
        }
        subscriber.close();
        context.term();
    }    
}

Publisher.java :

import java.util.Random;

import org.zeromq.ZMQ;
import org.zeromq.ZMQ.Context;
import org.zeromq.ZMQ.Socket;

public class Publisher {
    public static void main(String[] args) {
        String url = args[0];
        String topic = args[1];
        int intervall = Integer.valueOf(args[2]);

        Context context = ZMQ.context(1);
        Socket publisher = context.socket(ZMQ.PUB);

        Random rand = new Random();
        publisher.connect(url);
        while (!Thread.currentThread().isInterrupted()) {
            try {
                Thread.sleep(intervall);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            int value = rand.nextInt(20) * (rand.nextBoolean() ? (-1) : 1);
            publisher.sendMore(topic);
            publisher.send(String.valueOf(value));
            System.out.println("PUB: " + topic + ":" + value);
        }

        publisher.close();
        context.term();
    }
}

PubSubProxy.java :

import java.io.PrintStream;

import org.zeromq.ZContext;
import org.zeromq.ZFrame;
import org.zeromq.ZMQ;
import org.zeromq.ZMQ.Context;
import org.zeromq.ZMQ.Socket;
import org.zeromq.ZThread;
import org.zeromq.ZThread.IAttachedRunnable;

public class PubSubProxy {
    static Socket frontend;
    static Socket backend;

    public static void main(String[] args) {
        String addressSubscriber = args[0];
        String modeSubscriber = args[1];
        String addressPublisher = args[2];
        String modePublisher = args[3];

        // Prepare our context and sockets
        // ZContext context = ZMQ.context(1);
        ZContext context = new ZContext();

        // This is where the weather server sits
        frontend = context.createSocket(ZMQ.XSUB);
        if (modeSubscriber.equals("client")) {
            System.out.println("Subscriber connecting to: " + addressSubscriber);
            frontend.connect(addressSubscriber);
        } else if (modeSubscriber.equalsIgnoreCase("server")) {
            System.out.println("Subscriber binding to: " + addressSubscriber);
            frontend.bind(addressSubscriber);
        }
        // This is our public endpoint for subscribers
        backend = context.createSocket(ZMQ.XPUB);

        if (modePublisher.equals("client")) {
            System.out.println("Publisher connecting to: " + addressPublisher);
            backend.connect(addressPublisher);
        } else if (modePublisher.equalsIgnoreCase("server")) {
            System.out.println("Publisher binding to: " + addressPublisher);
            backend.bind(addressPublisher);
        }

        // Subscribe on everything
        // frontend.subscribe("".getBytes());

        // Run the proxy until the user interrupts us
        IAttachedRunnable runnable = new Listener();
        Socket listener = ZThread.fork(context, runnable);
        ZMQ.proxy(frontend, backend, listener);

        frontend.close();
        backend.close();
        context.destroy();
    }

    private static class Listener implements IAttachedRunnable {
        @Override
        public void run(Object[] args, ZContext ctx, Socket pipe) {
            // Print everything that arrives on pipe
            while (true) {
                ZFrame frame = ZFrame.recvFrame(pipe);
                if (frame == null)
                    break; // Interrupted
                System.out.println(frame.toString());
                frame.destroy();
            }
        }
    }
}

as you can see I have added a Listener to the proxy to see if I get the messages. On the publisher side proxy(the top one in the picture) I get the messages, but nothing on the other proxy.

this is the way I execute my applications

#beaglebone #1
#proxy #1
java -Djava.library.path=/usr/local/lib -jar proxy.jar ipc:///tmp/pub server tcp://*:5555 server 
#pub
java -Djava.library.path=/usr/local/lib -jar publisher.jar ipc:///tmp/pub temperature 10000
java -Djava.library.path=/usr/local/lib -jar publisher.jar ipc:///tmp/pub humidity 1000
java -Djava.library.path=/usr/local/lib -jar publisher.jar ipc:///tmp/pub testvar 5000

#beaglebone #2
#proxy #2
java -Djava.library.path=/usr/local/lib -jar proxy.jar tcp://192.168.0.192:5555 client ipc:///tmp/sub server
#sub
java -Djava.library.path=/usr/local/lib -jar subscriber.jar ipc:///tmp/sub temperature
java -Djava.library.path=/usr/local/lib -jar subscriber.jar ipc:///tmp/sub humidity
java -Djava.library.path=/usr/local/lib -jar subscriber.jar ipc:///tmp/sub testvar

pub-sub network

mpromonet
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user2071938
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1 Answers1

0

You seems to make confusions mixing client/server pattern with pub/sub pattern.

In the pub/sub pattern, the publisher notify its subscriber (if any). A publisher should use bind (to listen for subscriptions) and a subscriber should use connect (to request for a subscription).

Then your exchanges becomes : enter image description here

In order to do this you could :

  • modify Publisher.java replacing publisher.connect(url); with publisher.bind(url);
  • modify PubSubProxy.java removing useless client/server argument
import java.io.PrintStream;

import org.zeromq.ZContext;
import org.zeromq.ZFrame;
import org.zeromq.ZMQ;
import org.zeromq.ZMQ.Context;
import org.zeromq.ZMQ.Socket;
import org.zeromq.ZThread;
import org.zeromq.ZThread.IAttachedRunnable;

public class PubSubProxy {
    static Socket frontend;
    static Socket backend;

    public static void main(String[] args) {
        String addressSubscriber = args[0];
        String addressPublisher = args[1];

        // Prepare our context and sockets
        ZContext context = new ZContext();

        // This is where the weather server sits
        frontend = context.createSocket(ZMQ.XSUB);
        System.out.println("Subscriber connecting to: " + addressSubscriber);
        frontend.connect(addressSubscriber);

        // This is our public endpoint for subscribers
        backend = context.createSocket(ZMQ.XPUB);
        System.out.println("Publisher binding to: " + addressPublisher);
        backend.bind(addressPublisher);

        // Run the proxy until the user interrupts us
        ZMQ.proxy(frontend, backend, null);

        frontend.close();
        backend.close();
        context.destroy();
    }
}

Then you should be able to received data from backend to frontend using :

#beaglebone #1
#proxy #1
java -Djava.library.path=/usr/local/lib -jar proxy.jar ipc:///tmp/pub tcp://*:5555 
#pub
java -Djava.library.path=/usr/local/lib -jar publisher.jar ipc:///tmp/pub temperature 10000

#beaglebone #2
#proxy #2
java -Djava.library.path=/usr/local/lib -jar proxy.jar tcp://192.168.0.192:5555 ipc:///tmp/sub
#sub
java -Djava.library.path=/usr/local/lib -jar subscriber.jar ipc:///tmp/sub temperature
mpromonet
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