daytimed.c

comer s TCPIP-vol3源代码...当然是经典咯

/* daytimed.c - main */

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <netinet/in.h>

#include <unistd.h>
#include <stdio.h>
#include <string.h>

extern int	errno;

int	daytime(char buf[]);
int	errexit(const char *format, ...);
int	passiveTCP(const char *service, int qlen);
int	passiveUDP(const char *service);

#define	MAX(x, y)	((x) > (y) ? (x) : (y))

#define	QLEN		 32

#define	LINELEN		128

/*------------------------------------------------------------------------
 * main - Iterative server for DAYTIME service
 *------------------------------------------------------------------------
 */
int
main(int argc, char *argv[])
{
	char	*service = "daytime";	/* service name or port number	*/
	char	buf[LINELEN+1];		/* buffer for one line of text	*/
	struct sockaddr_in fsin;	/* the request from address	*/
	unsigned int	alen;		/* from-address length		*/
	int	tsock; 			/* TCP master socket		*/
	int	usock;			/* UDP socket			*/
	int	nfds;
	fd_set	rfds;			/* readable file descriptors	*/

	switch (argc) {
	case	1:
		break;
	case	2:
		service = argv[1];
		break;
	default:
		errexit("usage: daytimed [port]\n");
	}

	tsock = passiveTCP(service, QLEN);
	usock = passiveUDP(service);
	nfds = MAX(tsock, usock) + 1;	/* bit number of max fd	*/

	FD_ZERO(&rfds);

	while (1) {
		FD_SET(tsock, &rfds);
		FD_SET(usock, &rfds);

		if (select(nfds, &rfds, (fd_set *)0, (fd_set *)0,
				(struct timeval *)0) < 0)
			errexit("select error: %s\n", strerror(errno));
		if (FD_ISSET(tsock, &rfds)) {
			int	ssock;		/* TCP slave socket	*/

			alen = sizeof(fsin);
			ssock = accept(tsock, (struct sockaddr *)&fsin,
				&alen);
			if (ssock < 0)
				errexit("accept failed: %s\n",
						strerror(errno));
			daytime(buf);
			(void) write(ssock, buf, strlen(buf));
			(void) close(ssock);
		}
		if (FD_ISSET(usock, &rfds)) {
			alen = sizeof(fsin);
			if (recvfrom(usock, buf, sizeof(buf), 0,
				(struct sockaddr *)&fsin, &alen) < 0)
				errexit("recvfrom: %s\n",
					strerror(errno));
			daytime(buf);
			(void) sendto(usock, buf, strlen(buf), 0,
				(struct sockaddr *)&fsin, sizeof(fsin));
		}
	}
}

/*------------------------------------------------------------------------
 * daytime - fill the given buffer with the time of day
 *------------------------------------------------------------------------
 */
int
daytime(char buf[])
{
	char	*ctime();
	time_t	now;

	(void) time(&now);
	sprintf(buf, "%s", ctime(&now));
}