网络编程学习笔记(套接口超时)

有三种方法给套接口上的I/O操作设置 超时：

1、调用 alarm，在到达指定时间 时产生 SIGALRM信号，可能与进程中其他已有的alarm调用 冲突

2、使用select阻塞在等待I/O上，select内部有一个时间 限制，以此代替在read或write调用上阻塞

3、使用新的SO_RCVTIMEO和SO_SNDTIMEO套接口选项

1、signal设置recvfrom超时

服务器端，定时器设置为5s，5s内没有收到数据就触发告警信号

服务器端代码：

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

#define SERV_PORT 9999
#define BUF_LEN 128

static void sig_alrm(int signo)
{
	printf("alarm\n");
}



void dg_echo(int sockfd, struct sockaddr_in *pcliaddr, socklen_t clilen)
{
	char buf[BUF_LEN];	
	socklen_t len;
	int n;
	
	signal(SIGALRM, sig_alrm);
	for (;;) {
		alarm(5);
		len = clilen;
		if ((n = recvfrom(sockfd, buf, BUF_LEN, 0, (struct sockaddr*)pcliaddr, &clilen)) < 0) {
			if (errno == EINTR)  printf("alarm timeout\n");
			printf("recvfrom error:%s\n", strerror(errno));
			continue;
		} 
		alarm(0);
		sendto(sockfd, buf, n, 0, (struct sockaddr*)pcliaddr, len);
		
	}	
}

int main(int argc, char **argv)
{
	struct sockaddr_in servaddr, clientaddr;
	int sockfd;

	sockfd = socket(AF_INET, SOCK_DGRAM, 0);	
	if (sockfd < 0) {
		printf("socket error:%s\n", strerror(errno));
		return -1;
	}

	memset(&servaddr, 0x00, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
	servaddr.sin_port = htons(SERV_PORT);
	
	if (bind(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0) {
		printf("bind error:%s\n", strerror(errno));
		close(sockfd);	
		return -1;
	}
		
	dg_echo(sockfd, &clientaddr, sizeof(clientaddr));
	return 0;
}

客户端代码：

#include <sys/socket.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <netinet/in.h>

#define SERV_PORT 9999
#define BUF_LEN 128

void dg_cli(FILE *fp, int sockfd, const struct sockaddr_in * pservaddr, socklen_t servlen)
{
	int n;
	char sendline[BUF_LEN], recvline[BUF_LEN];
	
	while (fgets(sendline, BUF_LEN, fp) != NULL) {
		sendto(sockfd, sendline, strlen(sendline), 0, (struct sockaddr*)pservaddr, servlen);	
		n = recvfrom(sockfd, recvline, BUF_LEN, 0, NULL, NULL);
		recvline[n] = 0;
		fputs(recvline, stdout);
	}
}

int main(int argc, char **argv)
{
	struct sockaddr_in servaddr;
	int sock;

	memset(&servaddr, 0x00, sizeof(servaddr));	
	servaddr.sin_family = AF_INET;
	servaddr.sin_port = htons(SERV_PORT);	
	
	if (inet_pton(AF_INET, argv[1], &servaddr.sin_addr) < 0) {
		printf("inet_pton error:%s\n", strerror(errno));
		return -1;
	}

	sock = socket(AF_INET, SOCK_DGRAM, 0);	
	if (sock < 0) {
		printf("socket error:%s\n", strerror(errno));
		return -1;
	}

	dg_cli(stdin, sock, &servaddr, sizeof(servaddr));
	return 0;
}

2、select设置recvfrom超时

只修改服务器端代码，客户端保持不变。服务器代码如下：

#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <sys/select.h>
#include <sys/time.h>

#define SERV_PORT 9999
#define BUF_LEN 128

int readable_time(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);
}

void dg_echo(int sockfd, struct sockaddr_in *pcliaddr, socklen_t clilen)
{
	char buf[BUF_LEN];	
	socklen_t len;
	int n;
	
	for (;;) {
		len = clilen;
		if (readable_time(sockfd, 5) == 0) {
			printf("time out\n");
		} else if ((n = recvfrom(sockfd, buf, BUF_LEN, 0, (struct sockaddr*)pcliaddr, &clilen)) < 0) {
			if (errno == EINTR)  printf("alarm timeout\n");
			printf("recvfrom error:%s\n", strerror(errno));
			continue;
		} 
		sendto(sockfd, buf, n, 0, (struct sockaddr*)pcliaddr, len);
		
	}	
}

int main(int argc, char **argv)
{
	struct sockaddr_in servaddr, clientaddr;
	int sockfd;

	sockfd = socket(AF_INET, SOCK_DGRAM, 0);	
	if (sockfd < 0) {
		printf("socket error:%s\n", strerror(errno));
		return -1;
	}

	memset(&servaddr, 0x00, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
	servaddr.sin_port = htons(SERV_PORT);
	
	if (bind(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0) {
		printf("bind error:%s\n", strerror(errno));
		close(sockfd);	
		return -1;
	}
		
	dg_echo(sockfd, &clientaddr, sizeof(clientaddr));
	return 0;
}

输出为：

3、用SO_RCVTIMEO套接口选项设置 recvfrom超时

只修改服务器端，代码如下：

#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <sys/select.h>
#include <sys/time.h>

#define SERV_PORT 9999
#define BUF_LEN 128


void dg_echo(int sockfd, struct sockaddr_in *pcliaddr, socklen_t clilen)
{
	char buf[BUF_LEN];	
	socklen_t len;
	int n;
	
	for (;;) {
		len = clilen;
		
		if ((n = recvfrom(sockfd, buf, BUF_LEN, 0, (struct sockaddr*)pcliaddr, &clilen)) < 0) {
			if (errno == EWOULDBLOCK)  printf("alarm timeout\n");
			printf("recvfrom error:%s\n", strerror(errno));
			continue;
		} 
		sendto(sockfd, buf, n, 0, (struct sockaddr*)pcliaddr, len);
		
	}	
}

int main(int argc, char **argv)
{
	struct sockaddr_in servaddr, clientaddr;
	int sockfd;
	struct timeval tv;

	sockfd = socket(AF_INET, SOCK_DGRAM, 0);	
	if (sockfd < 0) {
		printf("socket error:%s\n", strerror(errno));
		return -1;
	}

	memset(&servaddr, 0x00, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
	servaddr.sin_port = htons(SERV_PORT);

	tv.tv_sec = 5;
	tv.tv_usec = 0;	
	if (setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)) < 0) {
		printf("setsockopt error:%s\n", strerror(errno));
	}		

	if (bind(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0) {
		printf("bind error:%s\n", strerror(errno));
		close(sockfd);	
		return -1;
	}
		
	dg_echo(sockfd, &clientaddr, sizeof(clientaddr));
	return 0;
}

输出为：