Synchronized publisher in C

// Synchronized publisher

#include "zhelpers.h"
#define SUBSCRIBERS_EXPECTED 10 //// We wait for 10 subscribers //

int main (void)
{
void *context = zmq_ctx_new ();

// Socket to talk to clients
void *publisher = zmq_socket (context, ZMQ_PUB);

int sndhwm = 1100000;
zmq_setsockopt (publisher, ZMQ_SNDHWM, &sndhwm, sizeof (int));

zmq_bind (publisher, "tcp://*:5561");

// Socket to receive signals
void *syncservice = zmq_socket (context, ZMQ_REP);
zmq_bind (syncservice, "tcp://*:5562");

// Get synchronization from subscribers
printf ("Waiting for subscribers\n");
int subscribers = 0;
while (subscribers < SUBSCRIBERS_EXPECTED) {
// - wait for synchronization request
char *string = s_recv (syncservice);
free (string);
// - send synchronization reply
s_send (syncservice, "");
subscribers++;
}
// Now broadcast exactly 1M updates followed by END
printf ("Broadcasting messages\n");
int update_nbr;
for (update_nbr = 0; update_nbr < 1000000; update_nbr++)
s_send (publisher, "Rhubarb");

s_send (publisher, "END");

zmq_close (publisher);
zmq_close (syncservice);
zmq_ctx_destroy (context);
return 0;
}