//
// Created by hlhd on 2020/12/25.
//

#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <errno.h>
#include <strings.h>
#include <signal.h>

const int MAX_BYTES = 4096;

void sig_handler(int sig)
{
    printf("signal %d\n", sig);
    while (waitpid(-1, NULL, WNOHANG) > 0);
}

int main(int argc, char** argv)
{
    struct sigaction sigact;
    sigact.sa_flags = SA_RESTART;
    sigact.sa_handler = sig_handler;
    sigemptyset(&sigact.sa_mask);
    sigaction(SIGCHLD, &sigact, NULL);

    char buf[MAX_BYTES];
    int clntfd;
    char IP_buf[INET_ADDRSTRLEN];
    struct sockaddr_in server_addr, clnt_addr;
    bzero(&clnt_addr, sizeof(clnt_addr));

    bzero(&server_addr, sizeof(server_addr));
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    server_addr.sin_port = htons(8888);
    server_addr.sin_family = AF_INET;

    int lstnfd = socket(AF_INET, SOCK_STREAM, 0);

    if (bind(lstnfd, (struct sockaddr*)&server_addr,
                sizeof(server_addr)) == -1)
    {
        perror("bind");
        exit(errno);
    }

    listen(lstnfd, 128);

    socklen_t addr_len;
    int ret;
    pid_t pid;

    while (1)
    {
        addr_len = sizeof(clnt_addr);
        printf("begin accept\n");

        clntfd = accept(lstnfd, (struct sockaddr*)&clnt_addr, &addr_len);
        if (clntfd == -1)
        {
            perror("accept");
            exit(-1);
        }
        pid = fork();
        if (pid == 0)
        {
            close(lstnfd);
            printf("accept from IP: %s Port : %d\n",
                   inet_ntop(AF_INET, &clnt_addr.sin_addr.s_addr,
                             IP_buf, sizeof(IP_buf)),
                             ntohs(clnt_addr.sin_port));
            while (1)
            {
                ret = read(clntfd, buf, sizeof(buf));
                if (ret == 0)
                {
                    printf("the other size is closed\n");
                    break;
                }
                else
                {
                    buf[ret] = '\0';
                    printf("read buf %s\n", buf);
                }
            }
            close(clntfd);
            exit(0);
        }
        else if (pid > 0)
        {
            continue;
        }
        else if (pid == -1) {
            perror("fork");
            exit(-1);
        }
        close(clntfd);
    }

    close(lstnfd);
    return 0;
}