telnet-client.c

/*
 * Sean Middleditch
 * sean@sourcemud.org
 *
 * The author or authors of this code dedicate any and all copyright interest
 * in this code to the public domain. We make this dedication for the benefit
 * of the public at large and to the detriment of our heirs and successors. We
 * intend this dedication to be an overt act of relinquishment in perpetuity of
 * all present and future rights to this code under copyright law. 
 */

#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <poll.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
#include <unistd.h>

#ifdef HAVE_ZLIB
#include "zlib.h"
#endif

#include "libtelnet.h"

static void _send(int sock, unsigned char *buffer, unsigned int size) {
	int rs;

	/* send data */
	while (size > 0) {
		if ((rs = send(sock, buffer, size, 0)) == -1) {
			fprintf(stderr, "send() failed: %s\n", strerror(errno));
			exit(1);
		} else if (rs == 0) {
			fprintf(stderr, "send() unexpectedly returned 0\n");
			exit(1);
		}

		/* update pointer and size to see if we've got more to send */
		buffer += rs;
		size -= rs;
	}
}

static void _event_handler(struct libtelnet_t *telnet,
		struct libtelnet_event_t *ev, void *user_data) {
	int sock = *(int*)user_data;

	switch (ev->type) {
	/* data received */
	case LIBTELNET_EV_DATA:
		write(STDOUT_FILENO, ev->buffer, ev->size);
		break;
	/* data must be sent */
	case LIBTELNET_EV_SEND:
		_send(sock, ev->buffer, ev->size);
		break;
	/* accept any options we want */
	case LIBTELNET_EV_NEGOTIATE:
		/* enable COMPRESS2 */
		if (ev->command == LIBTELNET_WILL &&
				ev->telopt == LIBTELNET_TELOPT_COMPRESS2)
			libtelnet_send_negotiate(telnet, LIBTELNET_DO, ev->telopt);
		break;
	/* error */
	case LIBTELNET_EV_ERROR:
		fprintf(stderr, "ERROR: %.*s\n", ev->size, ev->buffer);
		exit(1);
	default:
		/* ignore */
		break;
	}
}

int main(int argc, char **argv) {
	unsigned char buffer[512];
	int rs;
	int sock;
	struct sockaddr_in addr;
	struct pollfd pfd[2];
	struct libtelnet_t telnet;
	struct addrinfo *ai;
	struct addrinfo hints;

	/* check usage */
	if (argc != 3) {
		fprintf(stderr, "Usage:\n ./telnet-client <host> <port>\n");
		return 1;
	}

	/* look up server host */
	memset(&hints, 0, sizeof(hints));
	hints.ai_family = AF_UNSPEC;
	hints.ai_socktype = SOCK_STREAM;
	if ((rs = getaddrinfo(argv[1], argv[2], &hints, &ai)) != 0) {
		fprintf(stderr, "getaddrinfo() failed for %s: %s\n", argv[1],
				gai_strerror(rs));
		return 1;
	}
	
	/* create server socket */
	if ((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
		fprintf(stderr, "socket() failed: %s\n", strerror(errno));
		return 1;
	}

	/* bind server socket */
	memset(&addr, 0, sizeof(addr));
	addr.sin_family = AF_INET;
	if (bind(sock, (struct sockaddr *)&addr, sizeof(addr)) == -1) {
		fprintf(stderr, "bind() failed: %s\n", strerror(errno));
		return 1;
	}

	/* connect */
	if (connect(sock, ai->ai_addr, ai->ai_addrlen) == -1) {
		fprintf(stderr, "server() failed: %s\n", strerror(errno));
		return 1;
	}

	/* free address lookup info */
	freeaddrinfo(ai);

	/* initialize telnet box */
	libtelnet_init(&telnet, _event_handler, LIBTELNET_MODE_CLIENT, &sock);

	/* initialize poll descriptors */
	memset(pfd, 0, sizeof(pfd));
	pfd[0].fd = STDIN_FILENO;
	pfd[0].events = POLLIN;
	pfd[1].fd = sock;
	pfd[1].events = POLLIN;

	/* loop while both connections are open */
	while (poll(pfd, 2, -1) != -1) {
		/* read from stdin */
		if (pfd[0].revents & POLLIN) {
			if ((rs = read(STDIN_FILENO, buffer, sizeof(buffer))) > 0) {
				libtelnet_send_data(&telnet, buffer, rs);
			} else if (rs == 0) {
				break;
			} else {
				fprintf(stderr, "recv(server) failed: %s\n",
						strerror(errno));
				exit(1);
			}
		}

		/* read from client */
		if (pfd[1].revents & POLLIN) {
			if ((rs = recv(sock, buffer, sizeof(buffer), 0)) > 0) {
				libtelnet_push(&telnet, buffer, rs);
			} else if (rs == 0) {
				break;
			} else {
				fprintf(stderr, "recv(client) failed: %s\n",
						strerror(errno));
				exit(1);
			}
		}
	}

	/* clean up */
	libtelnet_free(&telnet);
	close(sock);

	return 0;
}