How to connect to Telnet server from Node.js ?

Difficulty Level : Expert
Last Updated : 17 Sep, 2021

In this article, we will see how to connect the Telnet server with Node.js application.

Telnet: The telnet is an application protocol over the Transmission Control Protocol (TCP) used on the internet or local area network to provide a bidirectional interactive text-oriented communication facility using a virtual terminal connection. Telnet is used to share a terminal with someone far from us. They provide lots of benefits like virtual terminals and real-time execution on command on the shared terminal. if you have more curious about the telnet refer to this article.

NodeJS: Node.js is a runtime environment for javascript, based on the V8 engine the executes javascript on the server-side. So with the help of nodejs we also create an event-driven application,if you have more curious about the telnet refer to this article.

Program Approach:

Firstly declare the same global variable for further use.
Import or require two modules for work with telnet server, first one is the net module the help to manage the network and the second one telnet-stream is used for establishing a connection with a telnet server.
Initialize net socket object with IP and port number of the telnet server.
Create a telnet client and connect this above socket.
After connection, the socket listing some events is as close for if connections are closed and data for collecting data from the telnet server last but not a least do and will event to occur every new step in telnet server create a log.

Connect the Telnet server from Node.js

Step 1: Run the below command for initializing npm.

npm init -y

Note: -y is used for all settings are default.

Step 2: install some packages.

npm install telnet-stream

Note: telnet-stream is used to connect the telnet to our node application.

Step 3: Create a file with the below code. Here, the filename is index.js

Javascript

// Some global variable for further use
var TelnetSocket, net, socket, tSocket;
 
// Require the net module for work with networking
net = require("net");
 
// Require and create a TelnetSocket Object
({ TelnetSocket } = require("telnet-stream"));
 
// Initialize the socket with the our ip and port
socket = net.createConnection(22, "test.rebex.net");
 
// Connect the socket with telnet
tSocket = new TelnetSocket(socket);
 
// If the connection are colose "close handler"
tSocket.on("close", function () {
    return process.exit();
});
 
// If the connection are on "on handler"
tSocket.on("data", function (buffer) {
    return process.stdout.write(buffer.toString("utf8"));
});
 
// If the connection are occure somethin "doing handler"
tSocket.on("do", function (option) {
    return tSocket.writeWont(option);
});
 
 
tSocket.on("will", function (option) {
    return tSocket.writeDont(option);
});
 
// If the connection are send teh data "data handler"
process.stdin.on("data", function (buffer) {
    return tSocket.write(buffer.toString("utf8"));
});