zmq常用通信模式

zmq是一个消息队列。可以在进程内、进程间、TCP、多播中，以消息为单位传输数据，而不是socket的字节流。官方主页上有下载、使用、文档，蛮全的。

常用模式有：Request-Reply，Publish-Subscribe，Parallel Pipeline。

Request-Reply

request

 zmq::context_t context (1);
 zmq::socket_t socket (context, ZMQ_REQ);
 //Send the request
 zmq::message_t request(6);
 memcpy ((void *)request.data(), "Hello", 5);
 socket.send(request);
 //Get the reply
 zmq::message_t reply;
 socket.recv(&reply);

server

 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 ((void *) reply.data (), "World", 5);
   socket.send (reply);
 }

Publish-Subscribe

publisher

 zmq::context_t context (1);
 zmq::socket_t publisher (context, ZMQ_PUB);
 publisher.bind("tcp://*:5556");
 publisher.send(message);

subscriber

 zmq::context_t context (1);
 zmq::socket_t subscriber (context, ZMQ_SUB);
 subscriber.connect("tcp://localhost:5556");
 const char *filter = "";
 subscriber.setsockopt(ZMQ_SUBSCRIBE, filter, strlen (filter));
 zmq::message_t update;
 subscriber.recv(&update);

Parallel Pipeline

ventilator

 zmq::context_t context (1);
 //  Socket to send messages on
 zmq::socket_t  sender(context, ZMQ_PUSH);
 sender.bind("tcp://*:5557");
 //  通知sink开始处理任务
 zmq::socket_t sink(context, ZMQ_PUSH);
 sink.connect("tcp://localhost:5558");
 zmq::message_t message(2);
 memcpy(message.data(), "0", 1);
 sink.send(message);
 //开始往pipeline发送数据
 message.rebuild(10);
 sprintf ((char *) message.data(), "%d", workload);
 sender.send(message);

worker

 zmq::context_t context(1);

 //  Socket to receive messages on
 zmq::socket_t receiver(context, ZMQ_PULL);
 receiver.connect("tcp://localhost:5557");

 //  Socket to send messages to
 zmq::socket_t sender(context, ZMQ_PUSH);
 sender.connect("tcp://localhost:5558");

 //  Process tasks forever
 while (1) {
   receiver.recv(&message);
   //  Send results to sink
   message.rebuild();
   sender.send(message);
 }

sink

 //  Prepare our context and socket
 zmq::context_t context(1);
 zmq::socket_t receiver(context,ZMQ_PULL);
 receiver.bind("tcp://*:5558");

 //  Wait for start of batch
 zmq::message_t message;
 receiver.recv(&message);
 //receive from worker
 receiver.recv(&message);