Linux Inter-process Communication Demo

ipc.c

/***************************************************
 *
 * Linux Inter-process Communication Demo
 *
 ***************************************************/

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>

// my inter-process communication socket path
#define MY_SOCK_PATH        "/run/myipcsp"
#define LISTEN_BACKLOG      50

#define handle_error(msg) \
    do { perror(msg); exit(EXIT_FAILURE); goto end; } while (0)

// @see https://linux.die.net/man/7/unix
#define MY_DOMAIN           AF_UNIX
#define MY_TYPE             SOCK_STREAM
#define MY_PROTOCOL         (0)

int main(int argc, char ** argv)
{
    // socket
    int sfd = 0, cfd = 0;
    struct sockaddr_un my_addr = { 0 }, peer_addr = { 0 };
    socklen_t peer_addr_size = 0;

    // process
    int flag = 1;
    pid_t pid = 0;

    // IO
    const static size_t buflen = 1024;
    const char buffer [buflen] = { 0 };
    ssize_t size = 0;

    ////////////////////////////////////////////////////////////////////////////

    my_addr.sun_family = MY_DOMAIN;
    strncpy(my_addr.sun_path, MY_SOCK_PATH, sizeof(my_addr.sun_path) - 1);

    pid = fork();

    if (pid < 0)
        handle_error("fork");

    if (pid == 0)
    {
        // child process
        cfd = socket(MY_DOMAIN, MY_TYPE, MY_PROTOCOL);

        if (connect(cfd, (struct sockaddr *) &my_addr, sizeof(struct sockaddr_un)) == -1)
            handle_error("connect");

        for (int i = 10; i > 0 && flag; i--)
        {
            strncpy((char *) buffer, "Hello world!", buflen - 1);

            if (send(cfd, buffer, buflen, 0) == -1)
                handle_error("send");
        }

        stop:

        flag = 0;

        strncpy((char *) buffer, "stop", buflen - 1);

        if (send(cfd, buffer, buflen, 0) == -1)
            handle_error("send");
    }
    else
    {
        // parent process

        sfd = socket(MY_DOMAIN, MY_TYPE, MY_PROTOCOL);

        if (sfd == -1)
            handle_error("socket");

        if (bind(sfd, (struct sockaddr *) &my_addr, sizeof(struct sockaddr_un)) == -1)
            handle_error("bind");

        if (listen(sfd, LISTEN_BACKLOG) == -1)
            handle_error("listen");

        peer_addr_size = sizeof(struct sockaddr_un);

        while (flag)
        {
            cfd = accept(sfd, (struct sockaddr *) &peer_addr, &peer_addr_size);

            if (cfd == -1)
                handle_error("accept");

            while (flag)
            {
                memset((void *) buffer, 0, buflen);

                size = recv(cfd, (void *) buffer, buflen, 0);

                if (size < 0)
                    handle_error("recv");

                printf("%s\n", buffer, buflen);

                if (strcoll("stop", buffer) == 0)
                {
                    flag = 0;
                    goto end;
                }
            }

            close(cfd);
        }
    }

    end:

    if (pid == 0)
    {
        if (flag)
            goto stop;
    }
    else
    {
        unlink(MY_SOCK_PATH);
    }

    if (sfd)
    {
        close(sfd);
        sfd = 0;
    }

    if (cfd)
    {
        close(cfd);
        cfd = 0;
    }

    flag = 0;

    return 0;
}