Выбор zmq сокета

$ ./hwserver 
Received 
Received 
Received first

$ ./hwclient first
Connecting to hello world server...
Sending Hello 0...

$ ./hwclient first
Connecting to hello world server...
Sending Hello 0...
Hello was send
Sending Hello 1...
Hello was send
Sending Hello 2...
Hello was send
Sending Hello 3...
Hello was send
Sending Hello 4...
Hello was send
Sending Hello 5...
Hello was send
Sending Hello 6...
Hello was send
Sending Hello 7...
Hello was send
Sending Hello 8...
Hello was send
Sending Hello 9...
Hello was send

$ ./hwserver 
Received CLIENT
Received CLIENT
Received 
Received first

Received CLIENT
Received CLIENT

#include <zmq.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <assert.h>

int main (void)
{
    // Socket to talk to clients
    void *context = zmq_ctx_new ();
    void *responder = zmq_socket (context, ZMQ_ROUTER);
    //zmq_setsockopt (responder, ZMQ_IDENTITY, "SERVER", 6);
    int rc = zmq_bind (responder, "tcp://*:5555");
    assert (rc == 0);
    int i=0;
    zmq_msg_t buffer;
    while (1) {
        zmq_msg_init (&buffer);
        rc=zmq_msg_recv( &buffer, responder, 0 );
        printf ("Received %s\n",zmq_msg_data(&buffer));
        zmq_msg_close (&buffer);
        //zmq_send (responder, strcat(buffer, ",Hello"), 6 + strlen(buffer) + 1, 0);
    }
    return 0;
}

#include <zmq.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>


int main (int argc, char * argv[])
{
    if(argc != 2){
        printf("Not enogh arguments\n");
        return -1;

    }
    printf ("Connecting to hello world server...\n");
    void *context = zmq_ctx_new ();
    void *requester = zmq_socket (context, ZMQ_REQ);
    zmq_setsockopt (requester, ZMQ_IDENTITY, "CLIENT", 6);
    zmq_connect (requester, "tcp://localhost:5555");
    int rc;
    int request_nbr;
    for (request_nbr = 0; request_nbr < 5; request_nbr++) {
        char buffer [255];
        printf ("Sending Hello %d...\n", request_nbr);
        sleep(1);
        rc=zmq_send (requester, argv[1], strlen(argv[1])+ 1, 0);
        if(rc == -1){
            perror("Can't send\n");
        }
        printf("Hello was send\n");
        //zmq_recv (requester, buffer, 255, 0);
    }
    zmq_close (requester);
    zmq_ctx_destroy (context);
    return 0;
}

$ ./hwserver 
Received CLIENT
Received З
Received first