Add initial implementation of Telnet client with basic command handling

Signed-off-by: Hammer1279 <hammer@ht-dev.de>

index.js

@@ -0,0 +1,101 @@
+import { createConnection } from 'net'
+
+const port = 23;
+const hostname = "localhost";
+const delayMs = 100; // Command delay in milliseconds
+
+export const IAC = Buffer.from([0xff]); // Interpret As Command
+export const DONT = Buffer.from([0xfe]); // Don't
+export const DO = Buffer.from([0xfd]); // Do
+export const WONT = Buffer.from([0xfc]); // Won't
+export const WILL = Buffer.from([0xfb]); // Will
+export const SB = Buffer.from([0xfa]); // Subnegotiation Begin
+export const GA = Buffer.from([0xf9]); // Go Ahead
+export const EL = Buffer.from([0xf8]); // Erase Line
+export const EC = Buffer.from([0xf7]); // Erase Character
+export const AYT = Buffer.from([0xf6]); // Are You There
+export const AO = Buffer.from([0xf5]); // Abort Output
+export const IP = Buffer.from([0xf4]); // Interrupt Process
+export const BRK = Buffer.from([0xf3]); // Break
+export const DM = Buffer.from([0xf2]); // Data Mark
+export const NOP = Buffer.from([0xf1]); // No Operation
+export const SE = Buffer.from([0xf0]); // Subnegotiation End
+
+// Common Telnet options or features
+export const ECHO = Buffer.from([0x01]); // Echo
+export const SUPPRESS_GO_AHEAD = Buffer.from([0x03]); // Suppress Go Ahead
+export const STATUS = Buffer.from([0x05]); // Status
+export const TIMING_MARK = Buffer.from([0x06]); // Timing Mark
+export const TERMINAL_TYPE = Buffer.from([0x18]); // Terminal Type
+export const NAWS = Buffer.from([0x1f]); // Negotiate About Window Size
+export const TERMINAL_SPEED = Buffer.from([0x20]); // Terminal Speed
+export const REMOTE_FLOW_CONTROL = Buffer.from([0x21]); // Remote Flow Control
+export const LINEMODE = Buffer.from([0x22]); // Line Mode
+export const ENVIRONMENT_VARIABLES = Buffer.from([0x24]); // Environment Variables
+
+// custom codes for own client
+export const CUSTOM_CLIENT_INIT = Buffer.from([0x80]); // Custom Client Initialization
+export const KEY_EXCHANGE = Buffer.from([0x81]); // Key Exchange
+export const ENCRYPTION = Buffer.from([0x82]); // Encryption
+export const AUTHENTICATION = Buffer.from([0x83]); // Authentication
+// 0x84 reserved for future use
+export const FILE_TRANSFER = Buffer.from([0x85]); // File Transfer
+export const PAUSE = Buffer.from([0x86]); // Pause
+export const RESUME = Buffer.from([0x87]); // Resume
+
+const socket = createConnection(port, hostname);
+
+process.stdin.setEncoding("ascii");
+process.stdin.setRawMode(true);
+process.stdin.resume();
+
+// format keys before sending to server
+process.stdin.on('data', (key) => {
+    if (key === '\u0003') { // Ctrl+C
+        process.exit();
+    }
+    
+    // Log hex values of input for debugging
+    // console.log("Key pressed:", Array.from(key).map(b => '0x' + b.toString(16)));
+    
+    if (key == "\r") {
+        // Enter key
+        socket.write("\r\n");
+    } else {
+        socket.write(key);
+    }
+});
+
+socket.on("data", (data) => {
+    if (data.equals(PAUSE)) {
+        process.stdin.pause();
+    } else if (data.equals(RESUME)) {
+        process.stdin.resume();
+    } else {
+        process.stdout.write(data);
+    }
+});
+
+socket.on("connect", async () => {
+    console.log("Connected to server");
+    socket.write(Buffer.concat([IAC, WILL, NAWS, SB, NAWS, Buffer.from([/* 24x80 */ 0x00, 0x18, 0x00, 0x50]), SE])); // Negotiate About Window Size
+    await delay(delayMs); // Wait for server to process
+    socket.write(Buffer.concat([IAC, WILL, TERMINAL_TYPE, IAC, SB, TERMINAL_TYPE, Buffer.from("xterm-256color"), IAC, SE])); // Terminal Type
+    await delay(delayMs);
+    socket.write(Buffer.concat([IAC, WILL, ECHO])); // Echo
+    await delay(delayMs);
+    socket.write(Buffer.from([0x0d, 0x0a])); // Line Feed
+    await delay(delayMs);
+    // initialization complete
+
+    await send("help");
+});
+
+export const delay = (ms) => new Promise(resolve => setTimeout(resolve, ms));
+
+export const send = async (command) => {
+    await delay(delayMs);
+    socket.write(command); // Command
+    await delay(delayMs);
+    socket.write("\r\n"); // Line Feed
+};

package-lock.json

@@ -0,0 +1,20 @@
+{
+  "name": "telnet-client",
+  "version": "1.0.0",
+  "lockfileVersion": 3,
+  "requires": true,
+  "packages": {
+    "": {
+      "name": "telnet-client",
+      "version": "1.0.0",
+      "license": "MIT",
+      "dependencies": {
+        "telnet-client": "file:"
+      }
+    },
+    "node_modules/telnet-client": {
+      "resolved": "",
+      "link": true
+    }
+  }
+}

package.json

@@ -0,0 +1,19 @@
+{
+  "name": "telnet-client",
+  "version": "1.0.0",
+  "description": "To be used with HTDev BBS Server for encrypted communication and extended functionality.",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://git.ht-dev.de/Hammer1279/node-telnet-client"
+  },
+  "author": "Hammer1279",
+  "license": "MIT",
+  "type": "module",
+  "dependencies": {
+    "telnet-client": "file:"
+  }
+}