An example of CZMQ Multicast using PUB/SUB

README.md

To use the scheme epgm:// or pgm:// you must configure libzmq 3.x (HEAD) using the --with-pgm.

./configure --with-pgm
./make
./make install

Remember to set you LD_LIBRARY_PATH to the location of the libzmq installation parameter For bash:

export LD_LIBRARY_PATH=/usr/local/lib

To compile publisher.c and subscriber.c

gcc -lzmq -lczmq -o publisher publisher.c
gcc -lzmq -lczmq -o subscriber subscriber.c

publisher.c

#include <stdio.h>
#include <czmq.h>

int main()
{
    // create the zeromq context
    void *ctx = zctx_new();
    void *pub = zsocket_new(ctx, ZMQ_PUB);
    zsocket_connect(pub, "epgm://192.168.10.114;239.192.1.1:5000"); 
    printf("multicast initialized\n");

    while(!zctx_interrupted) {
        zstr_sendm (pub, "testing", ZMQ_SNDMORE);
        zstr_send(pub, "This is a test");
    }

    return 0;
}

subscriber.c

#include <stdio.h>
#include <czmq.h>

int main()
{
    // create the zeromq context
    void *ctx = zctx_new();
    void *sub = zsocket_new(ctx, ZMQ_SUB);
    zsocket_connect(sub, "epgm://192.168.10.114;239.192.1.1:5000");
    zsocket_set_subscribe(sub, "testing");
    printf("multicast initialized\n");
  
    while(!zctx_interrupted) {
        zmsg_t *msg = zmsg_new();
        msg = zmsg_recv (sub);
	    printf("message size = %d\n" + zmsg_size(msg));
	
        int i;
	    for (i = 0; i < zmsg_size(msg); i++) {
	        printf("Data frame %d is %s\n", i, zframe_data(zmsg_next(msg)));
	    }
	    zmsg_destroy (&msg);
    }

    return 0;
}

Thanks for the examples. A couple of suggestions for improvement:

• insert a sleep statement in the publisher while loop to avoid CPU getting hogged and network getting flooded e.g. zclock_sleep (1000);
• In the subscriber, I found I was getting glitchy output when passing the byte* to printf. I got more consistent output by creating char* using zframe_strdup and passing that to printf e.g.

while(!zctx_interrupted) {
  zframe_t *identity = zmsg_pop (msg);
  zframe_t *content = zmsg_pop (msg);
  char * identity_str = zframe_strdup (identity);
  char * content_str = zframe_strdup (content);

  printf("identify: %s\n", identity_str);
  printf("content: %s\n", content_str);

  free(identity_str);
  free(content_str);

  zmsg_destroy (&msg);
 }

This uses PLAIN mechanism. Could you do an example that uses CURVE??

@ggitau, you can refer to this location for curve implementation but that might require some improvements.