force client into character mode

build.sh

@@ -7,6 +7,6 @@
 name="moxerver"
 
 include_dir="."
-src_list="$name.c server.c client.c tty.c"
+src_list="$name.c server.c client.c tty.c telnet.c"
 
 gcc $src_list -o $name -I $include_dir

client.c

@@ -23,26 +23,49 @@ int client_read(struct client_t *client) {
 		fprintf(stderr, "[%s:%d] error %d: %s\n", __func__, __LINE__, errno, strerror(errno));
 		return -errno;
 	}
-	/* null-terminate received data */
-	client->data[len] = '\0';
 	
-	//TODO how does a client disconnect? For now let's wait for QUIT command...
+	//TODO let's print received bytes during development phase...
-	if (!strncmp(client->data, "QUIT", 4)) {
+	{
-		client_close(client);
+		int i;
+		for(i = 0; i < len; i++) {
+			fprintf(stderr, "client %s <- %u '%c'\n",
+					client->ip_string,
+					(unsigned char) client->data[i],
+					(unsigned char) client->data[i]);
+		}	
 	}
 	
-	//TODO let's print the data during development phase...
+	/* handle special telnet characters coming from client */
-	fprintf(stderr, "client %s says: %s", client->ip_string, client->data);
+	telnet_handle_client_read(client->data, &len);
 	
-	return 0;
+	return len;
 }
 
 /* Sends data from a buffer to client. */
 int client_write(struct client_t *client, char *databuf, int datalen) {
+	
+	int len;
+	
+	/* handle special telnet characters to display them correctly on client */
+	telnet_handle_client_write(databuf, &datalen);
+	
+	//TODO let's print received bytes during development phase...
+	{
+		int i;
+		for(i = 0; i < len; i++) {
+			fprintf(stderr, "client %s -> %u '%c'\n",
+					client->ip_string,
+					(unsigned char) databuf[i],
+					(unsigned char) databuf[i]);
+		}	
+	}
+	
 	/* send data to client */
-	if (send(client->socket, databuf, datalen, 0) == -1) {
+	len = send(client->socket, databuf, datalen, 0);
+	if (len == -1) {
 		fprintf(stderr, "[%s:%d] error %d: %s\n", __func__, __LINE__, errno, strerror(errno));
 		return -errno;
 	}
-	return 0;
+	
+	return len;
 }

moxerver.c

@@ -2,12 +2,12 @@
 #include <unistd.h> /* getopt() */
 
 
-#define SERVER_WAIT_TIMEOUT 5 /* seconds for select() timeout in server loop */
+#define SERVER_WAIT_TIMEOUT 10 /* seconds for select() timeout in server loop */
 #define PORT_MIN 4001 /* minimum TCP port number */
 #define PORT_MAX 4008 /* maximum TCP port number */
 
 /* Prints help message. */
-void usage() {
+static void usage() {
 	//TODO maybe some styling should be done
 	fprintf(stderr, "Usage: moxerver -p tcp_port -t tty_path [-h]\n");
 	fprintf(stderr, "- tcp_port range [%d .. %d]\n\n", PORT_MIN, PORT_MAX);
@@ -82,7 +82,7 @@ int main(int argc, char *argv[]) {
 	//TODO this is a good place to create and start the TTY thread, use "tty_path" when opening device
 	
 	
-	/* loop with timeouts waiting for client connection */
+	/* loop with timeouts waiting for client connection and data*/
 	while (1) {
 		
 		/* setup parameters for select() */
@@ -114,6 +114,8 @@ int main(int argc, char *argv[]) {
 						fprintf(stderr, "problem accepting client\n");
 						continue;
 					}
+					/* put client in "character" mode */
+					telnet_set_character_mode(&client);
 				}
 				/* reject connection request if a client is already connected */
 				else {
@@ -124,12 +126,15 @@ int main(int argc, char *argv[]) {
 			if ( (client.socket != -1) && FD_ISSET(client.socket, &read_fds) ) {
 				/* read client data */
 				ret = client_read(&client);
-				if ( ret != 0) {
+				if ( ret < 0) {
 					/* print error but continue waiting for new data */
 					fprintf(stderr, "problem reading client\n");
 					continue;
 				}
-				//TODO we should send this data to TTY device
+				/* echo back to client */
+				client_write(&client, client.data, ret);
+				
+				//TODO we should send this data to TTY device here
 			}
 		}
 		if (ret == 0) {

moxerver.h

@@ -51,6 +51,14 @@ int client_read(struct client_t *client);
 int client_write(struct client_t *client, char *databuf, int datalen);
 
 
+/* Tells client to go into "character" mode. */
+int telnet_set_character_mode(struct client_t *client);
+/* Handles special characters in data buffer after receiving them from client. */
+int telnet_handle_client_read(char *databuf, int *datalen);
+/* Handles special characters in data buffer before sending to client. */
+int telnet_handle_client_write(char *databuf, int *datalen);
+
+
 /* Opens the tty device and configures it. */
 int tty_open(struct tty_t *tty_dev, char* path);
 /* Closes the tty device. */
@@ -61,3 +69,6 @@ int tty_reconfigure(struct tty_t *tty_dev, struct termios newttyset);
 int tty_read(struct tty_t *tty_dev);
 /* Sends data from a buffer to tty device. */
 int tty_write(struct tty_t *tty_dev, char *databuf, int datalen);
+
+
+

telnet.c

@@ -0,0 +1,145 @@
+#include "moxerver.h"
+
+
+/* structure for holding telnet option name and value */
+struct telnet_option_t {
+	const char *name;
+	char value;
+};
+
+/* supported telnet option values */
+struct telnet_option_t telnet_options[] = {
+	{"WILL", 251},
+	{"WONT", 252},
+	{"DO", 253},
+	{"DONT", 254},
+	{"IAC", 255},
+	{"ECHO", 1},
+	{"SGA", 3},
+	{"LINEMODE", 34},
+	{"SLE", 45}
+};
+#define TELNET_OPTIONS_COUNT 9 /* keep this up with the number of supported options */
+
+/* Returns telnet option name based on the value. */
+static const char* telnet_option_name(int value) {
+	int i;
+	for (i = 0; i < TELNET_OPTIONS_COUNT; i ++)
+		if (telnet_options[i].value == value)
+			return telnet_options[i].name;
+	return '\0';
+}
+
+/* Returns telnet option value based on the name. */
+static char telnet_option_value(const char* name) {
+	int i;
+	for (i = 0; i < TELNET_OPTIONS_COUNT; i ++)
+		if (!strcmp(telnet_options[i].name, name))
+			return telnet_options[i].value;
+	return 0;
+}
+
+/* Sends telnet option command. */
+int telnet_send_command(struct client_t *client, const char* option, const char* command) {
+	
+	char data[3];
+	
+	/* pack command */
+	data[0] = telnet_option_value("IAC");
+	data[1] = telnet_option_value(option);
+	data[2] = telnet_option_value(command);
+	
+	/* send command */
+	if (client_write(client, data, 3) <= 0) {
+		fprintf(stderr, "[%s:%d] failed sending %s %s\n", __func__, __LINE__, option, command);
+		return -1;
+	}
+	
+	fprintf(stderr, "[%s]: sent %s %s\n", __func__, option, command);
+	return 0;
+}
+
+/* Handles received telnet option command. */
+int telnet_handle_command(char *databuf, int datalen) {
+	
+	if (databuf[0] == telnet_option_value("IAC")) {
+		fprintf(stderr, "[%s]: received %s %s\n", __func__,
+				telnet_option_name(databuf[1]), telnet_option_name(databuf[2]));
+	}
+	
+	return 0;
+}
+
+/* Tells client to go into "character" mode. */
+int telnet_set_character_mode(struct client_t *client) {
+	
+	int err = 0;
+	
+	/* send predefined commands and add up their return vaules */
+	err += telnet_send_command(client, "WILL", "ECHO");
+	err += telnet_send_command(client, "WILL", "SGA");
+	err += telnet_send_command(client, "WONT", "LINEMODE"); /* this depends on telnet client */
+		
+	//TODO Do we verify client response? What do we do if the response is not how we expected?
+	
+	return err;
+}
+
+/* Handles special characters in data buffer after receiving them from client. */
+int telnet_handle_client_read(char *databuf, int *datalen) {	
+	
+	int i;
+	char newdata[DATA_BUFLEN];
+	int newlen = 0;
+	
+	/* process data using a new buffer */
+	for (i = 0; i < *datalen; i++) {
+		/* handle and discard telnet commands */
+		if (databuf[i] == telnet_option_value("IAC")) {
+			telnet_handle_command((databuf+i), 3);
+			i += 2;
+		}
+		/* let other data pass through */
+		else {
+			newdata[newlen++] = databuf[i];
+		}
+	}
+	/* overwrite data with new buffer */
+	for (i = 0; i < newlen; i++) databuf[i] = newdata[i];
+	*datalen = newlen;
+	
+	return 0;
+}
+
+/* Handles special characters in data buffer before sending to client. */
+int telnet_handle_client_write(char *databuf, int *datalen) {
+	
+	int i;
+	char newdata[DATA_BUFLEN];
+	int newlen = 0;
+	
+	/* process data using a new buffer */
+	for (i = 0; i < *datalen; i++) {
+		/* pressed ENTER */
+		if (databuf[i] == 13) {
+			fprintf(stderr, "[%s]: handling ENTER\n", __func__);
+			newdata[newlen++] = '\r';
+			newdata[newlen++] = '\n';
+		}
+		/* pressed BACKSPACE */
+		if (databuf[i] == 127) {
+			fprintf(stderr, "[%s]: handling BACKSPACE\n", __func__);
+			newdata[newlen++] = 8;
+			newdata[newlen++] = ' ';
+			newdata[newlen++] = 8;
+		}
+		else {
+			newdata[newlen++] = databuf[i];
+		}
+	}
+	/* overwrite data with new buffer */
+	for (i = 0; i < newlen; i++) databuf[i] = newdata[i];
+	*datalen = newlen;
+	
+	return 0;
+}