Tag Archives: linux

How to use Telnet

TL;DR; Telnet is a network protocol that allows a user on one computer to log into another computer that is part of the same network.

Telnet is a text based application, often used at the command line of an operating system. Most importantly it uses the Telnet protocol (which is part of the TCP/IP protocol suite) to connect to a remote computer over a network. Keep in mind, telnet is an external command, which is available in certain microsoft operating systems as telent.exe. Running the telnet application requires different set of commands on different operating systems.

telnet
how telnet works

Example:

prompt$ telnet kumar.swatantra.info 23

Usage:

# telnet [host [port]]
telnet servername-or-ip [port-number]

Ports are specific gateways for Internet traffic to travel over. It’s similar to a large hallway with many doors leading outside. If a door is locked, you cannot access the outside world.

Telnet syntax

telnet [host [port]]

host Specifies the hostname or IP address of the remote computer.
port Specifies the port number or service name.

Commands available through the actual telnet program:

close Close current connection.
display Display operating parameters.
open Connect to a site.
quit Exit telnet.
set Set options (Type ‘set ?’ for a list).

NTLM Turn ON NTLM Authentication.
LOCAL_ECHO Turn ON LOCAL_ECHO.
TERM x (where x is ANSI, VT100, VT52, or VTNT)
CRLF Send both CR and LF
status Print status information.
unset Unset options (Type ‘unset ?’ for a list).

NTLM Turn OFF NTLM Authentication.
LOCAL_ECHO Turn OFF LOCAL_ECHO.
CRLF Send only CR (no LF is sent)
?/help Print help information.

Linux

  1. Open the your terminal application
  2. At the shell prompt, type: telnet exampleserver.com 23
  3. On a normal Unix machine the port is just the second argument on the command line.

Windows

  1. Click the start button
  2. Choose “run” from the start menu
  3. Type “cmd.exe” in to the run box
  4. At the cmd prompt, type: telnet exampleserver.com 23

Mac OS X

  1. Open the Applications menu or folder
  2. Select the Utilities folder
  3. Start the Terminal.app application
  4. At the shell prompt, type: telnet exampleserver.com 23
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How to Enable and disable phpinfo()

The phpinfo() function is mostly disabled in the shared hosting service due to security reasons. phpinfo()is disabled, as it displays information which can be used to compromise the server. By disabling the phpinfo() one can take a step to secure the server, but it becomes difficult for debugging.

phpinfo()
phpinfo()

Here are steps for enabling and disabling the phpinfo() :-

You want to enable phpinfo

Considering you have access to the server’s php.ini file then edit this file in any editor e.g. vim. Search and change the disable_functions directive from disable_functions = phpinfo to disable_functions =

Considering you don’t have access to your server’s php.ini file (most likely case), you may be able to create your own php.ini file. And change the disable_functions directive that way in your own version of php.ini. If that doesn’t work, learn “How to debug php application with phpinfo() disabled ?

You want to disable phpinfo

Considering you have access to the server’s php.ini file, then change the line that includes the disable_functions directive so that it says disable_functions = phpinfo

Considering you don’t have access to your server’s php.ini file, you may be able to create your own php.ini file and change the disable_functions directive that way. Or, add a line in the application that says

ini_set('disable_functions', 'phpinfo');
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