/*********************************************************************************
 *      Copyright:  (C) 2025 LingYun IoT System Studio
 *                  All rights reserved.
 *
 *       Filename:  usocket_server.c
 *    Description:  This file unix domain socker server example program.
 *
 *        Version:  1.0.0(11/07/2025)
 *         Author:  Guo Wenxue <guowenxue@gmail.com>
 *      ChangeLog:  1, Release initial version on "11/07/2025 04:10:30 PM"
 *
 ********************************************************************************/
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>

#define SOCKET_PATH    "/tmp/example.sock" /* UNIX域socke 路径 */

int main(int argc, char **argv)
{
    int                     rv = -1;
    int                     listen_fd,  client_fd = -1;
    struct sockaddr_un      serv_addr;
    char                    buf[1024];

    /* 创建 UNIX域名socket(AF_UNIX), 也叫本地套接字(AF_LOCAL)  */
    listen_fd = socket(AF_UNIX /* 或使用 AF_LOCAL */, SOCK_STREAM, 0);
    if(listen_fd < 0 )
    {
        printf("create socket failure: %s\n", strerror(errno));
        return -1;
    }
    printf("socket create fd[%d]\n", listen_fd);

    /* 如果 socket 路径已存在则先删除 */
    if( !access(SOCKET_PATH, F_OK) )
    {
        unlink(SOCKET_PATH);
    }

    /* 设置 UNIX域socket 地址(路径) */
    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sun_family=AF_UNIX;
    strncpy(serv_addr.sun_path, SOCKET_PATH, sizeof(serv_addr.sun_path)-1);

    /* 绑定 UNIX域socket 地址  */
    if( bind(listen_fd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0 )
    {
        printf("create socket failure: %s\n", strerror(errno));
        unlink(SOCKET_PATH);
        return -2;
    }
    printf("socket[%d] bind on path \"%s\" ok\n", listen_fd, SOCKET_PATH);

    /* 下面的过程与网络 socket 编程完全一致 */

    listen(listen_fd, 13);

    while(1)
    {
        printf("\nStart waiting and accept new client connect...\n");
        client_fd = accept(listen_fd, NULL, NULL);
        if(client_fd < 0)
        {
            printf("accept new socket failure: %s\n", strerror(errno));
            return -2;
        }

        memset(buf, 0, sizeof(buf));
        if( (rv=read(client_fd, buf, sizeof(buf))) < 0)
        {
            printf("Read data from client socket[%d] failure: %s\n", client_fd, strerror(errno));
            close(client_fd);
            continue;
        }
        else if( rv == 0 )
        {
            printf("client socket[%d] disconnected\n", client_fd);
            close(client_fd);
            continue;
        }
        printf("read %d bytes data from client[%d] and echo it back: '%s'\n", rv, client_fd, buf);

        if( write(client_fd, buf, rv) < 0 )
        {
            printf("Write %d bytes data back to client[%d] failure: %s\n", rv, client_fd, strerror(errno));
            close(client_fd);
        }

        sleep(1);
        close(client_fd);
    }

    close(listen_fd);
}