Telnet in Windows

Introduction

TELNET (short for English teletype network) - a network protocol for implementing text terminal interface over the network (in modern form - using TCP transport). Some utilities that implement the client part of the protocol also have the name “telnet”. The current protocol standard is described in RFC 854.

It performs the functions of the OSI application layer protocol. The telnet protocol, along with ssh is widely used for remote administration by various network devices and software servers.

About telnet in Linux read the article «Telnet in Linux»

Installation

Control panel
Control Panel

Programmes and Components
(Programs and Features)

Turn Windows features on or off

Telnet Client

The alternative is to press. Windows key + R command

pkgmgr /iu:”TelnetClient”

Telnet client in Windows 10 looks as follows.

This is the so-called interactive mode.

Requested by command

?/help

Commands may be abbreviated. Supported commands are: c - close close current connection d - display display operating parameters o - open hostname [port] connect to hostname (default port 23). q - quit exit telnet set - set set options (type 'set ?' for a list) sen - send send strings to server st - status print status information u - unset unset options (type 'unset ?' for a list) ?/h - help print help information

If

d

Escape Character is 'CTRL+]' Will auth(NTLM Authentication) Local echo off New line mode - Causes return key to send CR & LF Current mode: Console Will term type Preferred term type is ANSI

I personally don’t like interactive mode and prefer to use telnet. from the command line or from Bash for Windows

Installation of telnet in wsl

sudo apt update

Get:1 http://deb.debian.org/debian buster InRelease [122 kB] Get:2 http://security.debian.org/debian-security buster/updates InRelease [65.4 kB] Get:3 http://deb.debian.org/debian buster-updates InRelease [49.3 kB] Get:4 http://ftp.debian.org/debian buster-backports InRelease [46.7 kB] Get:5 http://security.debian.org/debian-security buster/updates/main amd64 Packages [197 kB] Get:6 http://security.debian.org/debian-security buster/updates/main Translation-en [106 kB] Get:7 http://deb.debian.org/debian buster/main amd64 Packages [7,907 kB] Get:8 http://ftp.debian.org/debian buster-backports/main amd64 Packages [301 kB] Get:9 http://ftp.debian.org/debian buster-backports/main Translation-en [234 kB] Get:10 http://deb.debian.org/debian buster/main Translation-en [5,970 kB] Get:11 http://deb.debian.org/debian buster-updates/main amd64 Packages [7,380 B] Get:12 http://deb.debian.org/debian buster-updates/main Translation-en [5,166 B] Fetched 15.0 MB in 15s (982 kB/s) Reading package lists... Done Building dependency tree Reading state information... Done 24 packages can be upgraded. Run 'apt list --upgradable' to see them.

sudo apt install telnet

Reading package lists... Done Building dependency tree Reading state information... Done The following NEW packages will be installed: telnet 0 upgraded, 1 newly installed, 0 to remove and 24 not upgraded. Need to get 70.4 kB of archives. After this operation, 167 kB of additional disk space will be used. Get:1 http://deb.debian.org/debian buster/main amd64 telnet amd64 0.17-41.2 [70.4 kB] Fetched 70.4 kB in 0s (149 kB/s) Selecting previously unselected package telnet. (Reading database ... 9861 files and directories currently installed.) Preparing to unpack .../telnet_0.17-41.2_amd64.deb ... Unpacking telnet (0.17-41.2) ... Setting up telnet (0.17-41.2) ... update-alternatives: using /usr/bin/telnet.netkit to provide /usr/bin/telnet (telnet) in auto mode

Examples

andrei@DESKTOP-OP43ER5:~$ telnet httpbin.org 80

Trying 34.230.193.231... Connected to httpbin.org. Escape character is '^]'.

We add the following lines

GET / HTTP/1.1
Host: httpbin.org

Don’t be afraid to press Enter – once you can.

andrei@DESKTOP-OP43ER5:~$ telnet httpbin.org 80

Trying 34.230.193.231... Connected to httpbin.org. Escape character is '^]'. GET / HTTP/1.1 Host: httpbin.org

Now click Enter twice in a row and get the contents of the page.

HTTP/1.1 200 OK Date: Fri, 08 May 2020 18:28:53 GMT Content-Type: text/html; charset=utf-8 Content-Length: 9593 Connection: keep-alive Server: gunicorn/19.9.0 Access-Control-Allow-Origin: * Access-Control-Allow-Credentials: true <!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>httpbin.org</title> …

I don’t give the whole answer, but you can imagine that there will be content on the main page of httpbin.org.

Let's try POST.

andrei@DESKTOP-OP43ER5:~$ telnet httpbin.org 80

Trying 34.230.193.231... Connected to httpbin.org. Escape character is '^]'. POST /post HTTP/1.1 Host: httpbin.org Connection: close Content-type: application/json Content-length: 19 {"site":heihei.ru}

Number of characters in {"site":heihei.ru} equals 18.

Thus, if after {"site":heihei.rupress Enter, then translate the line becomes the 19th character and the message is processed.

If everything went well, then immediately after pressing Enter after closing the bracket, The following response will come from the server:

HTTP/1.1 200 OK Date: Fri, 08 May 2020 18:49:46 GMT Content-Type: application/json Content-Length: 355 Connection: close Server: gunicorn/19.9.0 Access-Control-Allow-Origin: * Access-Control-Allow-Credentials: true { "args": {}, "data": "{\"site\":heihei.ru}\r", "files": {}, "form": {}, "headers": { "Content-Length": "19", "Content-Type": "application/json", "Host": "httpbin.org", "X-Amzn-Trace-Id": "Root=1-5eb5a9c1-ae41c22c17663ab8255820a7" }, "json": null, "origin": "37.219.127.133", "url": "http://httpbin.org/post" } Connection closed by foreign host.

Let us pay attention to the following line:

"data": "{\"site\":heihei.ru}\r",

We'll send the same thing, but we'll increase the length by two characters.

andrei@DESKTOP-OP43ER5:~$ telnet httpbin.org 80

Trying 34.230.193.231... Connected to httpbin.org. Escape character is '^]'. POST /post HTTP/1.1 Host: httpbin.org Connection: close Content-type: application/json Content-length: 21 {"site":heihei.ru}

Now the message will leave only after the second press of Enter And in the answer, we'll see more characters in the same line.

The additional two characters are the new line \n and the translation of the carriage \r.

"data": "{\"site\":heihei.ru}\r\n\r",

Dynamic port

Escape Character is '^]' does not work

Try it.

CTRL+]

telnet>

telnet> quit

Connection closed.

Article author: Andrei Olegovich