udptimed.cpp

这是用c++编写的代码,用tcp,udp形式进行网络编程,代码很好.

/* UDPtimed.cpp - main */

#include <time.h>
#include <winsock.h>

SOCKET	passiveUDP(const char *);
void	errexit(const char *, ...);

#define	WINEPOCH	2208988800	/* Windows epoch, in UCT secs	*/
#define	WSVERS		      MAKEWORD(2, 0)

/*------------------------------------------------------------------------
 * main - Iterative UDP server for TIME service
 *------------------------------------------------------------------------
 */
int
main(int argc, char *argv[])
{
	struct sockaddr_in fsin;	/* the from address of a client	*/
	char	*service = "time";	/* service name or port number	*/
	char	buf[2048];	/* "input" buffer; any size > 1 packet	*/
	SOCKET	sock;			/* server socket		*/
	time_t	now;			/* current time			*/
	int	alen;			/* from-address length		*/
	WSADATA	wsadata;

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

	if (WSAStartup(WSVERS, &wsadata))
		errexit("WSAStartup failed\n");
	sock = passiveUDP(service);

	while (1) {
		alen = sizeof(fsin);
		if (recvfrom(sock, buf, sizeof(buf), 0,
		    (struct sockaddr *)&fsin, &alen) == SOCKET_ERROR)
			errexit("recvfrom: error %d\n", GetLastError());
		(void) time(&now);
		now = htonl((u_long)(now + WINEPOCH));
		(void) sendto(sock, (char *)&now, sizeof(now), 0,
			(struct sockaddr *)&fsin, sizeof(fsin));
	}
	return 1;	/* not reached */
}