← 返回第 13 章 多种 I/O 函数

oob_recv.c

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <fcntl.h>

#define BUF_SIZE 30
void error_handling(char *message);
void urg_handler(int signo);

int acpt_sock;
int recv_sock;

int main(int argc, char *argv[])
{
    struct sockaddr_in recv_adr, serv_adr;
    int str_len, state;
    socklen_t serv_adr_sz;
    struct sigaction act;
    char buf[BUF_SIZE];
    if (argc != 2)
    {
        printf("Usage : %s <port>\n", argv[0]);
        exit(1);
    }
    act.sa_handler = urg_handler;
    sigemptyset(&act.sa_mask);
    act.sa_flags = 0;

    acpt_sock = socket(PF_INET, SOCK_STREAM, 0);
    memset(&recv_adr, 0, sizeof(recv_adr));
    recv_adr.sin_family = AF_INET;
    recv_adr.sin_addr.s_addr = htonl(INADDR_ANY);
    recv_adr.sin_port = htons(atoi(argv[1]));

    if (bind(acpt_sock, (struct sockaddr *)&recv_adr, sizeof(recv_adr)) == -1)
        error_handling("bind() error");
    listen(acpt_sock, 5);

    serv_adr_sz = sizeof(serv_adr);
    recv_sock = accept(acpt_sock, (struct sockaddr *)&serv_adr, &serv_adr_sz);
    //将文件描述符 recv_sock 指向的套接字拥有者（F_SETOWN）改为把getpid函数返回值用做id的进程
    fcntl(recv_sock, F_SETOWN, getpid());
    state = sigaction(SIGURG, &act, 0); //SIGURG 是一个信号，当接收到 MSG_OOB 紧急消息时，系统产生SIGURG信号

    while ((str_len = recv(recv_sock, buf, sizeof(buf), 0)) != 0)
    {
        if (str_len == -1)
            continue;
        buf[str_len] = 0;
        puts(buf);
    }
    close(recv_sock);
    close(acpt_sock);
    return 0;
}
void urg_handler(int signo)
{
    int str_len;
    char buf[BUF_SIZE];
    str_len = recv(recv_sock, buf, sizeof(buf) - 1, MSG_OOB);
    if (str_len <= 0)
        return;
    buf[str_len] = 0;
    printf("Urgent message: %s \n", buf);
}

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