// 进程实现并发tcp通信
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <fcntl.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>

int main(int argc, char const *argv[])
{
    // 1. 创建 socket
    int sock_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (sock_fd < 0)
    {
        perror("socket");
        return 1;
    }

    // 2. bind
    struct sockaddr_in server_addr;
    bzero(&server_addr, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(atoi(argv[1]));
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);

    int flag = bind(sock_fd, (struct sockaddr *)&server_addr, sizeof(server_addr));
    if (flag != 0)
    {
        perror("bind");
        close(sock_fd);
        return 1;
    }

    // 3. 创建监听队列
    listen(sock_fd, 100);

    // 4. 开始接收客户端的连接（并发接收多个客户端）
    while (1)
    {
        struct sockaddr_in client_addr;
        bzero(&client_addr, sizeof(client_addr));
        socklen_t client_addr_len = sizeof(client_addr);

        int client_fd = accept(sock_fd, (struct sockaddr *)&client_addr, &client_addr_len);

        char clinet_ip[INET_ADDRSTRLEN] = "";
        inet_ntop(AF_INET, &client_addr.sin_addr.s_addr, clinet_ip, INET_ADDRSTRLEN);
        printf("%s 连接成功\n", clinet_ip);

        // 创建进程实现并发通信
        if (fork() == 0) // 子进程的作用域限制此范围
        {
            close(sock_fd); // 关闭父进程的socket文件描述符

            while (1)
            {
                char buf[128] = "";
                ssize_t len = recv(client_fd, buf, 128, 0);
                if (len > 0)
                {
                    int i = 0;
                    while (buf[i])
                    {
                        buf[i] = toupper(buf[i]);
                        i++;
                    }

                    send(client_fd, buf, len, 0);

                    if (strncmp(buf, "BYE", 3) == 0)
                    {
                        break;
                    }
                }
            }

            close(client_fd);
            printf("%s 关闭连接\n", clinet_ip);
            _exit(0); // 子进程完成后，自动关闭本子进程
        }
    }

    // 主进程的范畴
    close(sock_fd);

    return 0;
}