#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <signal.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define BACKLOG 16

int listen_fd = -1;

void sigINT(int signo);

int main()
{
    if (signal(SIGINT, sigINT) == SIG_ERR)
    {
        printf("set signal handler(SIGINT) error!!!\n");
        exit(1);
    }

    // socket
    if ( (listen_fd = socket(AF_INET6, SOCK_STREAM, 0)) < 0 )
    {
        printf("create socket error=%d(%s)!!!\n", errno, strerror(errno));
        exit(1);
    }

    // bind
    struct sockaddr_in6 server_addr;
    server_addr.sin6_family = AF_INET6; // IPv4
    server_addr.sin6_port = htons(12500); // Port
    server_addr.sin6_addr = in6addr_any; // IP
    if (bind(listen_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0)
    {
        printf("socket bind error=%d(%s)!!!\n", errno, strerror(errno));
        exit(1);
    }

    // listen
    if (listen(listen_fd, BACKLOG) < 0)
    {
        printf("socket listen error=%d(%s)!!!\n", errno, strerror(errno));
        exit(1);
    }

    printf("server init ok, start to accept new connect...\n");

    while (1)
    {
        // accept
        int client_fd = accept(listen_fd, NULL, NULL);
        if (client_fd < 0)
        {
            printf("socket accept error=%d(%s)!!!\n", errno, strerror(errno));
            exit(1);
        }
        printf("accept one new connect(%d)!!!\n", client_fd);

        static const char *msg = "Hello, Client!\n";
        if (write(client_fd, msg, strlen(msg)) != strlen(msg))
        {
            printf("send msg to client error!!!\n");
        }
        close(client_fd);
    }
}

void sigINT(int signo)
{
    printf("catch SIGINT, quit...\n");
    close(listen_fd);
    exit(0);
}