网络编程：多进程服务端

基于多进程的并发服务端模型

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

#define BUF_SIZE 30
void error_handling(char *message);
void read_childproc(int sig);

int main(int argc, char *argv[]) {
    int serv_sock, clnt_sock;
    struct sockaddr_in serv_adr, clnt_adr;
    
    pid_t pid;
    struct sigaction act;
    socklen_t adr_sz;
    int str_len, state;
    char buf[BUF_SIZE];
    if (argc != 2) {
        printf("usage: %s <port>\n", argv[0]);
        exit(1);
    }
	   //防止僵尸进程
	   //--------------
    act.sa_handler = read_childproc;
    sigemptyset(&act.sa_mask);
    act.sa_flags = 0;
    state = sigaction(SIGCHLD, &act, 0);
	  //---------------
    serv_sock = socket(PF_INET, SOCK_STREAM, 0);
    memset(&serv_adr, 0, sizeof(serv_adr));
    serv_adr.sin_family = AF_INET;
    serv_adr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_adr.sin_port = htons(atoi(argv[1]));
    
    if (bind(serv_sock, (struct sockaddr *)&serv_adr, sizeof(serv_adr)) == -1) {
        error_handling("bind() error");
    }
    if (listen(serv_sock, 5) == -1) {
        error_handling("listen() error");
    }
    
    while (1) {
        adr_sz = sizeof(clnt_adr);
        printf("adr_sz = %d \n", adr_sz);
        clnt_sock = accept(serv_sock, (struct sockaddr *)&clnt_adr, &adr_sz);
        
        if (clnt_sock == -1) {
            continue;
        } else {
            puts("new client connected...");
        }
        pid = fork();
        if (pid == -1) {
            close(clnt_sock);
            continue;
        }
        if (pid == 0) { //子进程
            close(serv_sock);
            while ((str_len = read(clnt_sock, buf, BUF_SIZE)) != 0) {
                write(clnt_sock, buf, str_len);
            }
            close(clnt_sock);
            puts("client disconnected...");
            return 0;
        } else {
			   //父进程关闭 clnt_sock，因为子进程已经有了复制的 clnt_sock
            close(clnt_sock);
        }
    }
     //子进程关闭 serv_sock，因为父进程有这个套接字
    close(serv_sock);
    return 0;
}

void read_childproc(int sig) {
    pid_t pid;
    int status;
    pid = waitpid(-1, &status, WNOHANG);
    printf("removed proc id: %d \n", pid);
}

void error_handling(char * message) {
    fputs(message, stderr);
    fputc('\n', stderr);
    exit(1);
}

为了关闭套接字，必须关闭所有文件描述符，调用fork()后，父子进程各有一个 serv 和 clnt 的文件描述符，因此需要先关闭一个。