Since Telnet connections are practically standard TCP connections, the client can be employed to use or test other services that rely on TCP as a transport protocol. For example, with a simple request, you can check the functionality of an HTTP server or (as mentioned earlier) the status of an e-mail server. This versatility is enhanced by the fact that the connection protocol can be used across platforms. There are only a few devices that do not support the official IETF standard. Whether or not the client and server computers rely on the same operating system is also irrelevant. A further advantage of Telnet is that it allows unrestricted access to a controlled system’s resources if permission has been given.
The latter point, however, presents a high-security risk when combined with a previously unmentioned disadvantage: neither the connection setup nor the data transmission is encrypted when the Telnet protocol is used. All information you send can, therefore, be intercepted by third parties in plain text, including the login information required for remote access. This means that hackers won’t have much trouble taking over the system.
An overview of the advantages and disadvantages: