example73.c

Linux网络编程教程适合初学者入门学习

/* example73.c */
#include	<sys/types.h>
#include	<sys/socket.h>
#include	<arpa/inet.h>
#include	<stdio.h>
#include	<string.h>
#include	<unistd.h>
#include	<signal.h>
#include	<errno.h>
#define		BUFLEN	255

void alarmed();
int
main(int argc, char **argv)
{
	struct sockaddr_in 	peeraddr, recvaddr, localaddr;
	int					sockfd;
	char 				recmsg[BUFLEN + 1];
	int					socklen, n;
	int 					rcvto = 3;
	struct sigaction		alrmact;
	memset(&alrmact, 0, sizeof(struct sigaction));
	alrmact.sa_handler = alarmed;
	alrmact.sa_flags = SA_NOMASK;
	alrmact.sa_restorer = NULL;
	sigaction(SIGALRM, &alrmact, NULL);
	if (argc != 5) {
		printf("%s <dest IP address> <dest port> <source IP address> <source port>\n", argv[0]);
		exit(0);
	}
	sockfd = socket(AF_INET, SOCK_DGRAM, 0);
	if (sockfd < 0) {
		fprintf(stderr, "socket creating error in udptalk.c!\n");
		exit(0);
	}
	socklen = sizeof(struct sockaddr_in);
	memset(&peeraddr, 0, socklen);
	peeraddr.sin_family = AF_INET;
	peeraddr.sin_port = htons(atoi(argv[2]));
	if (inet_pton(AF_INET, argv[1], &peeraddr.sin_addr) <= 0) {
		printf("Wrong dest IP address!\n");
		exit(0);
	}
	memset(&localaddr, 0, socklen);
	localaddr.sin_family = AF_INET;
	if (inet_pton(AF_INET, argv[3], &localaddr.sin_addr) <= 0) {
		printf("Wrong source IP address!\n");
		exit(0);
	}
	localaddr.sin_port = htons(atoi(argv[4]));
	if (bind(sockfd, &localaddr, socklen) < 0) {
		fprintf(stderr, "bind local address error in udptalk.c!\n");
		exit(0);
	}
	if (fgets(recmsg, BUFLEN, stdin) == NULL) 
		exit(0);
	if (sendto(sockfd, recmsg, strlen(recmsg), 0, &peeraddr, socklen) < 0) {
		fprintf(stderr, "sendto error in udptalk.c!\n");
		perror("");
		exit(3);
	}
	for ( ; ; ) {
		alarm(rcvto);
		n = recvfrom(sockfd, recmsg, BUFLEN, 0, &recvaddr, &socklen);
		if (n < 0) {
			alarm(0);
			if (errno != EINTR) {
				fprintf(stderr, "recvfrom error in udptalk.c!\n");
				perror("");
				exit(4);
			}
			else
				fprintf(stderr, "recvfrom timeout in udptalk.c!\n");
		}
		else {
			if (memcmp(&recvaddr, &peeraddr, socklen) != 0)
				continue;
			recmsg[n] = 0;
			printf("peer:%s", recmsg);
		}
		if (fgets(recmsg, BUFLEN, stdin) == NULL)
			exit(0);
		if (sendto(sockfd, recmsg, strlen(recmsg), 0, &peeraddr, socklen) < 0) {
			fprintf(stderr, "sendto error in udptalk.c!\n");
			perror("");
			exit(3);
		}
	}
}
void
alarmed(int signo)
{
	return;
}