Zeromq: PUB/SUB program using zmq, no exchange of messages

Question

I have written a simple PUB/SUB program in zmq which is not working. In server.c, all I am doing is binding server to specific socket and then broadcasting a message "Hi!, Similarly, in client.c, I am receving the sent string and printing it but it always skips the loop. When I run client it does not receive any message from server.c. What could possibly be wrong?

//server.c
#include <zmq.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>

int main (void)
{
    //  Prepare our context and publisher
    void *context = zmq_ctx_new ();
    void *publisher = zmq_socket (context, ZMQ_PUB);
    zmq_bind (publisher, "tcp://127.0.0.1:3333");
    char *string = "Hi!";

    while (1) {
        //  Send message to all subscribers
        zmq_msg_t message;
        zmq_msg_init_size (&message, strlen (string));
        memcpy (zmq_msg_data (&message), string, strlen (string));
        int rc = zmq_msg_send (publisher, &message, 0);
        zmq_msg_close (&message);
    }

    zmq_close (publisher);
    zmq_term (context);
    return 0;
}




//client.c
#include <zmq.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <assert.h>

int main (int argc, char *argv [])
{
    int rc;
    void *context = zmq_ctx_new ();

    //  Socket to talk to server
    printf ("Collecting updates from server...\n");
    void *subscriber = zmq_socket (context, ZMQ_SUB);

    rc = zmq_connect (subscriber, "tcp://127.0.0.1:3333");
    assert (rc == 0);

      while(1){

    // Receive message from server
      zmq_msg_t message;
      zmq_msg_init (&message);
      if(zmq_msg_recv (subscriber, &message, 0))
      continue;
      int size = zmq_msg_size (&message);
      char *string = malloc (size + 1);
      memcpy (string, zmq_msg_data (&message), size);
      zmq_msg_close (&message);
      string [size] = 0;
      printf("Message is: %s\n",string);
      }

    zmq_close (subscriber);
    zmq_term (context);
    return 0;
}

Answer 1

SUB 一方必须“订阅”某些东西

只需添加使用zmq_setsockopt( subscriber, ZMQ_SUBSCRIBE, "", 0 )after .connect(), 将其设置为订阅过滤器，使其成为默认值 < *nothing* >以外的任何内容，这会导致不通过 SUB 端过滤器传递任何内容（直到更改此设置）。

有关详细信息，请查看有关PUB/SUB行为和.setsockopt()的 ZeroMQ 文档。