UNIX(网络编程-IO操作):08---套接字超时

一、套接字超时的三种设置方法

• 三种方法的区别

二、使用SIGALRM信号为connect设置超时

static void	connect_alarm(int);

int connect_timeo(int sockfd, const SA *saptr, socklen_t salen, int nsec)
{
	Sigfunc	*sigfunc;
	int		n;

	sigfunc = Signal(SIGALRM, connect_alarm);
	if (alarm(nsec) != 0)
		err_msg("connect_timeo: alarm was already set");

	if ( (n = connect(sockfd, saptr, salen)) < 0) {
		close(sockfd);
		if (errno == EINTR)
			errno = ETIMEDOUT;
	}
	alarm(0);					/* turn off the alarm */
	Signal(SIGALRM, sigfunc);	/* restore previous signal handler */

	return(n);
}

static void connect_alarm(int signo)
{
	return;		/* just interrupt the connect() */
}
/* end connect_timeo */

• 函数介绍

.

• 注意事项

 

三、使用SIGALRM信号为recvfrom设置超时

 

static void	sig_alrm(int);

void dg_cli(FILE *fp, int sockfd, const SA *pservaddr, socklen_t servlen)
{
	int	n;
	char	sendline[MAXLINE], recvline[MAXLINE + 1];

	Signal(SIGALRM, sig_alrm);

	while (Fgets(sendline, MAXLINE, fp) != NULL) {

		Sendto(sockfd, sendline, strlen(sendline), 0, pservaddr, servlen);

		alarm(5);
		if ( (n = recvfrom(sockfd, recvline, MAXLINE, 0, NULL, NULL)) < 0) {
			if (errno == EINTR)
				fprintf(stderr, "socket timeout\n");
			else
				err_sys("recvfrom error");
		} else {
			alarm(0);
			recvline[n] = 0;	/* null terminate */
			Fputs(recvline, stdout);
		}
	}
}

static void sig_alrm(int signo)
{
	return;			/* just interrupt the recvfrom() */
}

• 函数介绍

四、使用select为recvfrom设置超时

int readable_timeo(int fd, int sec)
{
	fd_set			rset;
	struct timeval	tv;

	FD_ZERO(&rset);
	FD_SET(fd, &rset);

	tv.tv_sec = sec;
	tv.tv_usec = 0;

	return(select(fd+1, &rset, NULL, NULL, &tv));
		/* 4> 0 if descriptor is readable */
}

• 函数介绍

改版的dg_cli函数

void dg_cli(FILE *fp, int sockfd, const SA *pservaddr, socklen_t servlen)
{
	int	n;
	char	sendline[MAXLINE], recvline[MAXLINE + 1];

	while (Fgets(sendline, MAXLINE, fp) != NULL) {

		Sendto(sockfd, sendline, strlen(sendline), 0, pservaddr, servlen);

		if (Readable_timeo(sockfd, 5) == 0) {
			fprintf(stderr, "socket timeout\n");
		} else {
			n = Recvfrom(sockfd, recvline, MAXLINE, 0, NULL, NULL);
			recvline[n] = 0;	/* null terminate */
			Fputs(recvline, stdout);
		}
	}
}

五、使用SO_RCVTIMEO套接字选项为recvfrom设置超时

void dg_cli(FILE *fp, int sockfd, const SA *pservaddr, socklen_t servlen)
{
	int				n;
	char			sendline[MAXLINE], recvline[MAXLINE + 1];
	struct timeval	tv;

	tv.tv_sec = 5;
	tv.tv_usec = 0;
	Setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));

	while (Fgets(sendline, MAXLINE, fp) != NULL) {

		Sendto(sockfd, sendline, strlen(sendline), 0, pservaddr, servlen);

		n = recvfrom(sockfd, recvline, MAXLINE, 0, NULL, NULL);
		if (n < 0) {
			if (errno == EWOULDBLOCK) {
				fprintf(stderr, "socket timeout\n");
				continue;
			} else
				err_sys("recvfrom error");
		}

		recvline[n] = 0;	/* null terminate */
		Fputs(recvline, stdout);
	}
}

• 函数介绍