daytimeudpcli3.c

unix网络编程卷1：套接口API的全书源码

#include	"unp.h"

int
main(int argc, char **argv)
{
	int		sockfd, n, nq;
	char	recvline[MAXLINE + 1];
	socklen_t	salen;
	struct sockaddr	*sa;

	if (argc != 3)
		err_quit("usage: a.out <hostname or IPaddress> <service or port#>");

	sockfd = Udp_client(argv[1], argv[2], (void **) &sa, &salen);

	printf("sending to %s\n", Sock_ntop_host(sa, salen));

	Sendto(sockfd, "", 1, 0, sa, salen);	/* send 1-byte datagram */

	n = Recvfrom(sockfd, recvline, MAXLINE, MSG_PEEK, NULL, NULL);

	Ioctl(sockfd, FIONREAD, &nq);	/* check FIONREAD support */
	printf("%d bytes from PEEK, %d bytes pending\n", n, nq);

	n = Recvfrom(sockfd, recvline, MAXLINE, 0, NULL, NULL);
	recvline[n] = 0;	/* null terminate */
	Fputs(recvline, stdout);

	exit(0);
}