多进程并发服务器代码学习

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

// 进程回收函数
void recyle()
{
    pid_t pid;
    while((pid = waitpid(-1, NULL, WNOHANG)) > 0 ) {
        printf("child process died, pid = %d\n", pid);
    }
}

int main(int argc, const char* argv[])
{
    if (argc < 2) {
        printf("eg: ./a.out port\n");
        exit(EXIT_SUCCESS); 
    } 
    struct sockaddr_in serv_addr;
    socklen_t serv_len = sizeof(serv_addr);
    int port = atoi(argv[1]);

    // 创建套接子
    int lfd = socket(AF_INET, SOCK_STREAM, 0);
    // 初始化服务器sockaddr_in
    memset(&serv_addr, 0, serv_len);
    serv_addr.sin_family = AF_INET;                     //地址族
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);      //监听本机所有IP
    serv_addr.sin_port = htons((uint16_t)port);         //设置端口

    // 绑定IP和端口
    bind(lfd, (struct sockaddr*)&serv_addr, serv_len);
    
    // 设置同时监听的最大个数
    listen(lfd, 36);
    printf("Start accept .........");
    
    // 使用信号回收子进程pcb
    struct sigaction act;
    act.sa_handler = recyle;
    act.sa_flags = 0;
    sigemptyset(&act.sa_mask);
    sigaction(SIGCHLD, &act, NULL);

    struct sockaddr_in client_addr;
    socklen_t cli_len = sizeof(client_addr);
    while(1) {
        // 父进程接收连接请求
        int cfd = accept(lfd, (struct sockaddr*)&client_addr, &cli_len);
        while (cfd == -1 && errno == EINTR) {
            cfd = accept(lfd, (struct sockaddr*)&client_addr, &cli_len);
        }
        // 创建子进程
        pid_t pid = fork();
        if (pid ==0) {
            close(lfd);
            // child process
            // 通信
            char ip[64] = {0};
            while(1) {
                // 打印client ip port
                printf("client IP: %s, port: %d\n",
                        inet_ntop(AF_INET, &client_addr.sin_addr.s_addr, ip, sizeof(ip)),
                        ntohs(client_addr.sin_port));
                char buf[1024];
                int len = read(cfd, buf, sizeof(buf));
                if (len == -1) {
                    perror("read error");
                    exit(EXIT_FAILURE);
                }
                else if (len == 0) {
                    printf("客户端断开了连接");
                    close(cfd);
                    break;
                }
                else {
                    printf("recv buf: %s\n", buf);
                    write(cfd, buf, len);
                }
            } 
            // 干掉子进程
            return EXIT_SUCCESS;
        }
        else if (pid > 0) {
            close(cfd); 
            // parent process
            // 回收子进程 
        }
    } 
    return EXIT_SUCCESS;
}