zeromq forking - child process terminates inherited zeromq context

gistfile1.cpp

//
//  main.c
//  zmq-test1
//
//  Created by Matt Connolly on 8/08/2013.
//

//#include <ZeroMQ/zmq.h>
#include <czmq.h>

const char* address = "tcp://127.0.0.1:6571";

void my_handler(int, siginfo_t *info, void *uap);

zctx_t* context;

int main(int argc, const char * argv[])
{
    int rc;
    
    printf("parent process: %d\n", getpid());
    
    struct sigaction action;
    action.sa_flags = SA_SIGINFO;
    action.sa_mask = 0;
    sigemptyset(&action.sa_mask);
    action.sa_sigaction = &my_handler;
//    action.sa_sigaction = NULL;
    
    rc = sigaction(SIGCHLD, &action, NULL);
    assert(rc == 0);

    context = zctx_new();
    
    void* sock = zsocket_new(context, ZMQ_PULL);
    zsocket_bind(sock, address);

    // ensure io threads are running before fork
    sleep(1);
    
    pid_t child_pid = fork();
    if (child_pid == 0)
    {
        // child process
        printf("child: process id = %d\n", (int)getpid());
        sleep(1);
        zctx_destroy(&context);
        printf("child: destroyed context inherited from parent\n");
        
        sleep(1);
        void* ctx2 = zmq_ctx_new();
        void* sock = zmq_socket(ctx2, ZMQ_PUSH);
        zmq_connect(sock, address);
        const char* message = "hello";
        
        int i;
        for (i = 0; i < 9; i += 1) {
            printf("child: send message\n");
            zmq_send(sock, message, strlen(message), 0);
            usleep(1);
        }
        zmq_close(sock);
        zmq_ctx_destroy(ctx2);
        printf("child: destroyed child context\n");
        
        printf("child: done\n");
        exit(0);
    }
    else
    {
        // parent process
        char* buffer;
        zframe_t* frame;
        
        int i = 0;
        int received_count = 0;
        while (received_count < 3)
        {
            printf("parent waiting for message #%d...\n", i++);
            frame = zframe_recv(sock);
            if (frame) {
                received_count += 1;
                buffer = zframe_strdup(frame);
                printf("Received: %s\n", buffer);
                free(buffer);
                zframe_destroy(&frame);
            }
            else {
                printf("recv interrupted!\n");
            }
        }
        
        printf("parent: closing socket\n");
        zsocket_destroy(context, sock);
        zctx_destroy(&context);

        printf("parent: done\n");
    }
    return 0;
}

void my_handler(int signal, siginfo_t *info, void *uap)
{
    printf("signal %d received, from child pid %d!\n", signal, info->si_pid);
}