udpechod.c

来自「Error Exit Code for Linux operating syst」· C语言 代码 · 共 55 行

/* UDPechod.c - main */

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

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

#include <errno.h>
extern int	errno;

#define	BUFSIZE		4096

int	passiveUDP(const char *service);
int	errexit(const char *format, ...);


/*------------------------------------------------------------------------
 * main - Iterative UDP server for ECHO service
 *------------------------------------------------------------------------
 */
int
main(int argc, char *argv[])
{
	struct sockaddr_in fsin;	/* the from address of a client	*/
	char	*service = "echo";	/* service name or port number	*/
	char	buf[BUFSIZE];			  /* "input" buffer; any size > 0	*/
	int	sock;			/* server socket		*/
	
	unsigned int	alen;		/* from-address length		*/

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

	sock = passiveUDP(service);

	while (1) {
		alen = sizeof(fsin);
		if (recvfrom(sock, buf, sizeof(buf), 0,
				(struct sockaddr *)&fsin, &alen) < 0)
			errexit("recvfrom: %s\n", strerror(errno));
		
		(void) sendto(sock, buf, sizeof(buf), 0,
			(struct sockaddr *)&fsin, sizeof(fsin));
	}
}