broker.js

var pubListener = 'tcp://127.0.0.1:5555';
var subListener = 'tcp://127.0.0.1:5556';
var hwm = 1000;
var verbose = 0;

// The xsub listener is where pubs connect to
var subSock = zmq.socket('xsub');
subSock.identity = 'subscriber' + process.pid;
subSock.bindSync(subListener);

// The xpub listener is where subs connect to
var pubSock = zmq.socket('xpub');
pubSock.identity = 'publisher' + process.pid;
pubSock.setsockopt(zmq.ZMQ_SNDHWM, hwm);
// By default xpub only signals new subscriptions
// Settings it to verbose = 1 , will signal on every new subscribe
pubSock.setsockopt(zmq.ZMQ_XPUB_VERBOSE, verbose);
pubSock.bindSync(pubListener);

// When we receive data on subSock , it means someone is publishing
subSock.on('message', function(data) {
  // We just relay it to the pubSock, so subscribers can receive it
 pubSock.send(data);
});

// When Pubsock receives a message , it's subscribe requests
pubSock.on('message', function(data, bla) {
  // The data is a slow Buffer
  // The first byte is the subscribe (1) /unsubscribe flag (0)
  var type = data[0]===0 ? 'unsubscribe' : 'subscribe';
  // The channel name is the rest of the buffer
  var channel = data.slice(1).toString();
  console.log(type + ':' + channel);
  // We send it to subSock, so it knows to what channels to listen to
  subSock.send(data);
});

publisher.js

// Beware if pub is started before a subcriber listening, it just goes into /dev/null space

var zmq = require('zmq');
var sock = zmq.socket('pub');

// Instead of binding our pub socket, we connect to the PUB -> XSUB
sock.connect('tcp://127.0.0.1:5556');
sock.send('MYCHANNEL ' + 'here is the info');

subcriber.js

var zmq = require('zmq');
var sock = zmq.socket('sub');

// We subscribe to MYCHANNEL only
sock.subscribe('MYCHANNEL');

// We connect our sub -> XPUB channel
sock.connect('tcp://127.0.0.1:5555');

// When a message comes, 
sock.on('message', function(data) {
 // data is a SlowBuffer
 // data contains : 'MYCHANNEL' + aspace + 'here is the info'
 console.log(data.toString());
});