/* 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 *------------------------------------------------------------------------ */intmain(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 *------------------------------------------------------------------------ */intdaytime(char buf[]){	char	*ctime();	time_t	now;	(void) time(&now);	sprintf(buf, "%s", ctime(&now));}