Lazy Pirate client in C

//
// Lazy Pirate client
// Use zmq_poll to do a safe request-reply
// To run, start lpserver and then randomly kill/restart it
//

#include "czmq.h"

#define REQUEST_TIMEOUT 2500 // msecs, (> 1000!)
#define REQUEST_RETRIES 3 // Before we abandon
#define SERVER_ENDPOINT "tcp://localhost:5555"

int main (void)
{
zctx_t *ctx = zctx_new ();
printf ("I: connecting to server…\n");
void *client = zsocket_new (ctx, ZMQ_REQ);
assert (client);
zsocket_connect (client, SERVER_ENDPOINT);

int sequence = 0;
int retries_left = REQUEST_RETRIES;
while (retries_left && !zctx_interrupted) {
// We send a request, then we work to get a reply
char request [10];
sprintf (request, "%d", ++sequence);
zstr_send (client, request);

int expect_reply = 1;
while (expect_reply) {
// Poll socket for a reply, with timeout
zmq_pollitem_t items [] = { { client, 0, ZMQ_POLLIN, 0 } };
int rc = zmq_poll (items, 1, REQUEST_TIMEOUT * ZMQ_POLL_MSEC);
if (rc == -1)
break; // Interrupted

// If we got a reply, process it
if (items [0].revents & ZMQ_POLLIN) {
// We got a reply from the server, must match sequence
char *reply = zstr_recv (client);
if (!reply)
break; // Interrupted
if (atoi (reply) == sequence) {
printf ("I: server replied OK (%s)\n", reply);
retries_left = REQUEST_RETRIES;
expect_reply = 0;
}
else
printf ("E: malformed reply from server: %s\n",
reply);

free (reply);
}
else
if (--retries_left == 0) {
printf ("E: server seems to be offline, abandoning\n");
break;
}
else {
printf ("W: no response from server, retrying…\n");
// Old socket is confused; close it and open a new one
zsocket_destroy (ctx, client);
printf ("I: reconnecting to server…\n");
client = zsocket_new (ctx, ZMQ_REQ);
zsocket_connect (client, SERVER_ENDPOINT);
// Send request again, on new socket
zstr_send (client, request);
}
}
}
zctx_destroy (&ctx);
return 0;
}