My first socket program using nanomsg as in-proc communication method.

ipc_client.c

#include <nanomsg/nn.h>
#include <nanomsg/pair.h>
#include <stdio.h>

int main() {
    int s = nn_socket(AF_SP, NN_PAIR);
    int nbytes;
    char ch;
    char str[100];

    nn_connect(s, "ipc://test.ipc");
    while (ch = getchar()) {
        sprintf(str, "%c\0", ch);
        nbytes = nn_send(s, str, 2, 0);
        if (nbytes < 0)
            printf("%s\n", nn_strerror(errno));
    }

    return 0;
}

ipc_server.c

#include <nanomsg/nn.h>
#include <nanomsg/pair.h>
#include <stdio.h>
#include <assert.h>

int main() {
    int s = nn_socket(AF_SP, NN_PAIR);
    char buf[100];
    int nbytes;

    assert(s >= 0);

    nn_bind(s, "ipc://test.ipc");
    while (1) {
        nbytes = nn_recv(s, buf, sizeof(buf), 0);
        if (nbytes < 0)
            printf("%s\n", nn_strerror(errno));
        else
            printf("%s", buf);
    }

    return 0;
}

nanomsg_server.c

#include <nanomsg/nn.h>
#include <nanomsg/pair.h>
#include <assert.h>
#include <stdio.h>
#include <nanomsg/inproc.h>

int handle_error() {
    printf("%s\n", nn_strerror(errno));
    return 0;
}

int main() {
    int sa = nn_socket(AF_SP, NN_PAIR);
    int sb = nn_socket(AF_SP, NN_PAIR);
    int eid1, eid2;
    char buf[100];
    int nbytes;

    assert(sa >= 0);

    eid2 = nn_connect(sa, "inproc://test");
    assert(eid2 >= 0);

    eid1 = nn_bind(sb, "inproc://test");
    assert(eid1 >= 0);

    nbytes = nn_send(sa, "def\0", 4, 0);

    nbytes = nn_recv(sb, buf, sizeof(buf), 0);
    if (nbytes >= 0)
        printf("%s\n", buf);
    else {
        handle_error();
    }
    
    return 0;
}

The trap is when initializing socket using nn_socket. I first tried NN_PUB, and failed for a thousand times, after changed to NN_PAIR, everything was fine.