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What is Telnet?

Telnet is a Network Protocol which allows a person on one computer log into another computer remotely which is on same network. Telnet was developed in 1969, for the next 14 years it was improved and in 1983 it became part of Internet Standard# 8. Once a connection is established to the remote computer (host) , you can access files and data just as local user on remote host.

Telnet is a client-server protocol which requires a Telnet client and Telnet Server for communication. Using telnet client software on local computer, connection can be initiated to the telnet server which is the remote host. Once the connection is successfully established to the remote host, local computer can access resources as
if it is the local terminal connected to the telnet server. Telnet enables a user at one site to establish TCP connection to remote server. It uses TCP port number 23.Since Telnet uses TCP (Transmission Control Protocol) it is reliable and connection-oriented protocol.

What has changed since the development of Telnet?

Prior to the invent of Telnet, if someone wanted to access the server he had to walk to the server room to connect and gain access to it. At most places only one or two person was allowed at a time inside the server room due to which lot of time was lost in waiting for the entry inside the server location. Post the development of Telnet, we got the privilege of gaining the access of the server remotely which saves lot of time and effort in travelling to the server location. It also allowed multiple users to connect to the telnet server at the same time simultaneously.

Working of Telnet:

. A user on the local computer can initiate telnet program by typing below on command prompt:

Telnet xx.xxx.xxx.xxx 

This command is Telnet followed by either the host name or it’s IP Address.

. This command makes the Telnet client on local computer establish a TCP connection with the Telnet Server on remote host.
. Once the connection is established, one character at a time is sent to the Telnet Server upon each keystroke on Client’s end.
. Remote host treats the remote user as a local users who is logged into it.
. Remote host send the output back to the Telnet Server, which forwards it to the Telnet client and is displayed on the local user’s screen.

Limitations of Telnet:

When Telnet was invented there were no high speed internet , no hackers, no encryption and so Telnet became really popular which was widely used especially to gain access to remote system within a closed Network. But with the advancement of internet , there were loopholes that came up when people started using Telnet more often. The biggest drawback of using Telnet is it is Not Secure. The data sent and received using Telnet is in plain text and can be hacked easily. Even the personal information like username and password is sent in simple text format which could be sniffed and used to gain unauthorized access.
This gave birth to a more secure protocol known as SSH.

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