example74.c

Linux网络编程教程适合初学者入门学习

/* example74.c */
#include	<sys/types.h>
#include	<sys/socket.h>
#include	<arpa/inet.h>
#include	<stdio.h>
#include	<fcntl.h>
#include	<errno.h>
#include	<string.h>
#define		BUFLEN	255

int
main(int argc, char **argv)
{
	struct sockaddr_in 	peeraddr, localaddr;
	int			sockfd, stdinfd, n, maxfd, socklen, flags;
	char 			msg[BUFLEN + 1];
	fd_set			infds;
	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);
	}
	flags = fcntl(sockfd, F_GETFL, 0);
	flags |= O_NONBLOCK;
	fcntl(sockfd, F_SETFL, 0);
	stdinfd = fileno(stdin);
	flags = (fcntl(stdinfd, F_GETFL, 0));
	flags |= O_NONBLOCK;
	fcntl(stdinfd, F_SETFL, flags);
	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(2);
	}
	connect(sockfd, &localaddr, socklen);
	for ( ; ; ) {
		n = read(sockfd, &peeraddr, socklen);
		if (n == -1) {
			if (errno != EWOULDBLOCK) {
				printf("talk colsed by peer\n");
				exit(3);
			}
		}
		else {
			msg[n] = 0;
			printf("peer: %s", msg);
		}
		n = read(stdinfd, msg, BUFLEN);
		switch(n) {
			case -1:
				if (errno != EWOULDBLOCK) {
					fprintf(stderr, "stdin error\n");
					exit(4);
				}
				break;
			case 0:
				printf("talk over!\n");
				exit(0);
				break;
			default:
				write(sockfd, msg, n);
				msg[n] = 0;
				printf("sent: %s", msg);
		}	
	}
}