tcpecho.c

comer s TCPIP-vol3源代码...当然是经典咯

/* TCPecho.c - main, TCPecho */

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

extern int	errno;

int	TCPecho(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 ECHO service
 *------------------------------------------------------------------------
 */
int
main(int argc, char *argv[])
{
	char	*host = "localhost";	/* host to use if none supplied	*/
	char	*service = "echo";	/* default service name		*/

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

/*------------------------------------------------------------------------
 * TCPecho - send input to ECHO service on specified host and print reply
 *------------------------------------------------------------------------
 */
int
TCPecho(const char *host, const char *service)
{
	char	buf[LINELEN+1];		/* buffer for one line of text	*/
	int	s, n;			/* socket descriptor, read count*/
	int	outchars, inchars;	/* characters sent and received	*/

	s = connectTCP(host, service);

	while (fgets(buf, sizeof(buf), stdin)) {
		buf[LINELEN] = '\0';	/* insure line null-terminated	*/
		outchars = strlen(buf);
		(void) write(s, buf, outchars);

		/* read it back */
		for (inchars = 0; inchars < outchars; inchars+=n ) {
			n = read(s, &buf[inchars], outchars - inchars);
			if (n < 0)
				errexit("socket read failed: %s\n",
					strerror(errno));
		}
		fputs(buf, stdout);
	}
}