tcpdaytime.c

comer s TCPIP-vol3源代码...当然是经典咯

/* TCPdaytime.c - TCPdaytime, main */

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

extern int	errno;

int	TCPdaytime(const char *host, const char *service);
int	errexit(const char *format, ...);
int	connectTCP(const char *host, const char *service);

#define	LINELEN		128

/*------------------------------------------------------------------------
 * main - TCP client for DAYTIME service
 *------------------------------------------------------------------------
 */
int
main(int argc, char *argv[])
{
	char	*host = "localhost";	/* host to use if none supplied	*/
	char	*service = "daytime";	/* default service port		*/

	switch (argc) {
	case 1:
		host = "localhost";
		break;
	case 3:
		service = argv[2];
		/* FALL THROUGH */
	case 2:
		host = argv[1];
		break;
	default:
		fprintf(stderr, "usage: TCPdaytime [host [port]]\n");
		exit(1);
	}
	TCPdaytime(host, service);
	exit(0);
}

/*------------------------------------------------------------------------
 * TCPdaytime - invoke Daytime on specified host and print results
 *------------------------------------------------------------------------
 */
TCPdaytime(const char *host, const char *service)
{
	char	buf[LINELEN+1];		/* buffer for one line of text	*/
	int	s, n;			/* socket, read count		*/

	s = connectTCP(host, service);

	while( (n = read(s, buf, LINELEN)) > 0) {
		buf[n] = '\0';		/* ensure null-terminated	*/
		(void) fputs( buf, stdout );
	}
}