dgclibcast6.c

《Unix网络编程》的源代码的bcast部分

#include	"unp.h"

static void	recvfrom_alarm(int);
static int	pipefd[2];

void
dg_cli(FILE *fp, int sockfd, const SA *pservaddr, socklen_t servlen)
{
	int				n, maxfdp1;
	const int		on = 1;
	char			sendline[MAXLINE], recvline[MAXLINE + 1];
	fd_set			rset;
	socklen_t		len;
	struct sockaddr	*preply_addr;
 
	preply_addr = Malloc(servlen);

	Setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on));

	Pipe(pipefd);
	maxfdp1 = max(sockfd, pipefd[0]) + 1;

	FD_ZERO(&rset);

	Signal(SIGALRM, recvfrom_alarm);

	while (Fgets(sendline, MAXLINE, fp) != NULL) {
		Sendto(sockfd, sendline, strlen(sendline), 0, pservaddr, servlen);

		alarm(5);
		for ( ; ; ) {
			FD_SET(sockfd, &rset);
			FD_SET(pipefd[0], &rset);
			if ( (n = select(maxfdp1, &rset, NULL, NULL, NULL)) < 0) {
				if (errno == EINTR)
					continue;
				else
					err_sys("pselect error");
			}

			if (FD_ISSET(sockfd, &rset)) {
				len = servlen;
				n = Recvfrom(sockfd, recvline, MAXLINE, 0, preply_addr, &len);
				recvline[n] = 0;	/* null terminate */
				printf("from %s: %s",
						Sock_ntop_host(preply_addr, servlen), recvline);
			}

			if (FD_ISSET(pipefd[0], &rset)) {
				Read(pipefd[0], &n, 1);		/* timer expired */
				break;
			}
		}
	}
}

static void
recvfrom_alarm(int signo)
{
	Write(pipefd[1], "", 1);	/* write 1 null byte to pipe */
	return;
}