/* include udpserv1 */#include	"unpifi.h"void	mydg_echo(int, SA *, socklen_t, SA *);intmain(int argc, char **argv){	int					sockfd;	const int			on = 1;	pid_t				pid;	struct ifi_info		*ifi, *ifihead;	struct sockaddr_in	*sa, cliaddr, wildaddr;	for (ifihead = ifi = Get_ifi_info(AF_INET, 1);		 ifi != NULL; ifi = ifi->ifi_next) {			/*4bind unicast address */		sockfd = Socket(AF_INET, SOCK_DGRAM, 0);		Setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));		sa = (struct sockaddr_in *) ifi->ifi_addr;		sa->sin_family = AF_INET;		sa->sin_port = htons(SERV_PORT);		Bind(sockfd, (SA *) sa, sizeof(*sa));		printf("bound %s\n", Sock_ntop((SA *) sa, sizeof(*sa)));		if ( (pid = Fork()) == 0) {		/* child */			mydg_echo(sockfd, (SA *) &cliaddr, sizeof(cliaddr), (SA *) sa);			exit(0);		/* never executed */		}/* end udpserv1 *//* include udpserv2 */		if (ifi->ifi_flags & IFF_BROADCAST) {				/* 4try to bind broadcast address */			sockfd = Socket(AF_INET, SOCK_DGRAM, 0);			Setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));			sa = (struct sockaddr_in *) ifi->ifi_brdaddr;			sa->sin_family = AF_INET;			sa->sin_port = htons(SERV_PORT);			if (bind(sockfd, (SA *) sa, sizeof(*sa)) < 0) {				if (errno == EADDRINUSE) {					printf("EADDRINUSE: %s\n",						   Sock_ntop((SA *) sa, sizeof(*sa)));					continue;				} else					err_sys("bind error for %s",							Sock_ntop((SA *) sa, sizeof(*sa)));			}			printf("bound %s\n", Sock_ntop((SA *) sa, sizeof(*sa)));			if ( (pid = Fork()) == 0) {		/* child */				mydg_echo(sockfd, (SA *) &cliaddr, sizeof(cliaddr),						  (SA *) sa);				exit(0);		/* never executed */			}		}	}/* end udpserv2 *//* include udpserv3 */		/* 4bind wildcard address */	sockfd = Socket(AF_INET, SOCK_DGRAM, 0);	Setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));	bzero(&wildaddr, sizeof(wildaddr));	wildaddr.sin_family = AF_INET;	wildaddr.sin_addr.s_addr = htonl(INADDR_ANY);	wildaddr.sin_port = htons(SERV_PORT);	Bind(sockfd, (SA *) &wildaddr, sizeof(wildaddr));	printf("bound %s\n", Sock_ntop((SA *) &wildaddr, sizeof(wildaddr)));	if ( (pid = Fork()) == 0) {		/* child */		mydg_echo(sockfd, (SA *) &cliaddr, sizeof(cliaddr), (SA *) sa);		exit(0);		/* never executed */	}	exit(0);}/* end udpserv3 *//* include mydg_echo */voidmydg_echo(int sockfd, SA *pcliaddr, socklen_t clilen, SA *myaddr){	int			n;	char		mesg[MAXLINE];	socklen_t	len;	for ( ; ; ) {		len = clilen;		n = Recvfrom(sockfd, mesg, MAXLINE, 0, pcliaddr, &len);		printf("child %d, datagram from %s", getpid(),			   Sock_ntop(pcliaddr, len));		printf(", to %s\n", Sock_ntop(myaddr, clilen));		Sendto(sockfd, mesg, n, 0, pcliaddr, clilen);	}}/* end mydg_echo */