Parallel task ventilator in C++

//
// Task ventilator in C++
// Binds PUSH socket to tcp://localhost:5557
// Sends batch of tasks to workers via that socket
//
// Olivier Chamoux <moc.puorgselaht.rf|xuomahc.reivilo#moc.puorgselaht.rf|xuomahc.reivilo>
//

#include <zmq.hpp>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <iostream>

#define within(num) (int) ((float) num * random () / (RAND_MAX + 1.0))

int main (int argc, char *argv[])
{
zmq::context_t context (1);

// Socket to send messages on
zmq::socket_t sender(context, ZMQ_PUSH);
sender.bind("tcp://*:5557");

std::cout << "Press Enter when the workers are ready: " << std::endl;
getchar ();
std::cout << "Sending tasks to workers…\n" << std::endl;

// The first message is "0" and signals start of batch
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);

// Initialize random number generator
srandom ((unsigned) time (NULL));

// Send 100 tasks
int task_nbr;
int total_msec = 0; // Total expected cost in msecs
for (task_nbr = 0; task_nbr < 100; task_nbr++) {
int workload;
// Random workload from 1 to 100msecs
workload = within (100) + 1;
total_msec += workload;

message.rebuild(10);
memset(message.data(), '\0', 10);
sprintf ((char *) message.data(), "%d", workload);
sender.send(message);
}
std::cout << "Total expected cost: " << total_msec << " msec" << std::endl;
sleep (1); // Give 0MQ time to deliver

return 0;
}