telnet-client

What is telnet-client?

The telnet-client npm package is a simple and easy-to-use library for creating and managing Telnet connections in Node.js. It allows you to connect to Telnet servers, send commands, and receive responses, making it useful for automating tasks, remote server management, and network device configuration.

What are telnet-client's main functionalities?

Establishing a Telnet Connection

This feature allows you to establish a connection to a Telnet server using specified parameters such as host, port, shell prompt, and timeout.

const Telnet = require('telnet-client');
let connection = new Telnet();

let params = {
  host: '127.0.0.1',
  port: 23,
  shellPrompt: '/ # ',
  timeout: 1500
};

connection.connect(params)
  .then(() => {
    console.log('Connected to the Telnet server');
  })
  .catch((error) => {
    console.error('Connection failed:', error);
  });

Sending Commands

Once connected, you can send commands to the Telnet server and handle the responses. This is useful for executing remote commands and automating tasks.

connection.send('ls -l')
  .then((response) => {
    console.log('Command response:', response);
  })
  .catch((error) => {
    console.error('Command failed:', error);
  });

Handling Connection Events

You can handle various connection events such as timeout and close to manage the connection lifecycle and handle errors or disconnections gracefully.

connection.on('timeout', () => {
  console.log('Connection timed out');
  connection.end();
});

connection.on('close', () => {
  console.log('Connection closed');
});

Other packages similar to telnet-client

node-telnet-client

node-telnet-client is another Telnet client library for Node.js. It offers similar functionalities to telnet-client, such as establishing connections, sending commands, and handling responses. However, it provides a more extensive set of options for connection parameters and event handling, making it a bit more flexible for advanced use cases.

telnet-stream

telnet-stream is a low-level Telnet client library that provides a stream-based interface for Telnet communication. It is more suitable for developers who need fine-grained control over the Telnet protocol and want to build custom Telnet clients. Compared to telnet-client, it requires more effort to set up and use but offers greater flexibility.

README

node-telnet-client

A simple telnet client for node.js

Installation

Locally in your project or globally:

npm install telnet-client
npm install -g telnet-client

Example usage

var telnet = require('telnet-client');
var connection = new telnet();

var params = {
  host: '127.0.0.1',
  port: 23,
  shellPrompt: '/ # ',
  timeout: 1500,
  // removeEcho: 4
};

connection.on('ready', function(prompt) {
  connection.exec(cmd, function(response) {
    console.log(response);
  });
});

connection.on('timeout', function() {
  console.log('socket timeout!')
  connection.end();
});

connection.on('close', function() {
  console.log('connection closed');
});

connection.connect(params);

API

var telnet = require('telnet-client');
var connection = new telnet();

connection.connect(options)

Creates a new TCP connection to the specified host, where 'options' is an object which can include following properties:

• host: Host the client should connect to. Defaults to '127.0.0.1'.
• port: Port the client should connect to. Defaults to '23'.
• timeout: Sets the socket to timeout after the specified number of milliseconds of inactivity on the socket.
• shellPrompt: Shell prompt that the host is using. Defaults to regex '/(?:/ )?#\s/'.
• loginPrompt: Username/login prompt that the host is using. Defaults to regex '/login[: ]*$/i'.
• passwordPrompt: Username/login prompt that the host is using. Defaults to regex '/Password: /i'.
• username: Username used to login. Defaults to 'root'.
• password: Username used to login. Defaults to 'guest'.
• irs: Input record separator. A separator used to distinguish between lines of the response. Defaults to '\r\n'.
• ors: Output record separator. A separator used to execute commands (break lines on input). Defaults to '\n'.
• echoLines: The number of lines used to cut off the response. Defaults to 1.
• pageSeparator: The pattern used (and removed from final output) for breaking the number of lines on output. Defaults to '---- More'.

connection.exec(data, [options], [callback])

Sends data on the socket (should be a compatible remote host's command if sane information is wanted). The optional callback parameter will be executed when the data is finally written out - this may not be immediately. Command result will be passed as the first argument to the callback.

Options:

• shellPrompt: Shell prompt that the host is using. Defaults to regex '/(?:/ )?#\s/'.
• loginPrompt: Username/login prompt that the host is using. Defaults to regex '/login[: ]*$/i'.
• timeout: Sets the socket to timeout after the specified number of milliseconds of inactivity on the socket.
• irs: Input record separator. A separator used to distinguish between lines of the response. Defaults to '\r\n'.
• ors: Output record separator. A separator used to execute commands (break lines on input). Defaults to '\n'.
• echoLines: The number of lines used to cut off the response. Defaults to 1.

connection.end()

Half-closes the socket. i.e., it sends a FIN packet. It is possible the server will still send some data.

connection.destroy()

Ensures that no more I/O activity happens on this socket. Only necessary in case of errors (parse error or so).

Event: 'connect'

Emitted when a socket connection is successfully established.

Event: 'ready'

Emitted when a socket connection is successfully established and the client is successfully connected to the specified remote host. A value of prompt is passed as the first argument to the callback.

Event: 'writedone'

Emitted when the write of given data is sent to the socket.

Event: 'timeout'

Emitted if the socket times out from inactivity. This is only to notify that the socket has been idle. The user must manually close the connection.

Event: 'error'

Emitted when an error occurs. The 'close' event will be called directly following this event.

Event: 'end'

Emitted when the other end of the socket (remote host) sends a FIN packet.

Event: 'close'

Emitted once the socket is fully closed.