What does VTN do?

Network Virtual Terminal (NVT) is a network virtual terminal protocol, which means that all terminals on the network provide similar interfaces to any host process. In this way, any terminal supported by the network and any host system on the network can be used together.

TELNET uses symmetric data representation. When each client sends data, it maps the character representation of its local terminal to the character representation of VTN, and when receiving data, it maps the representation of VTN to the local character set.

principle of operation

At both ends of the client/server system where Telnet connection is established, information is transmitted in local format. The client program converts the user's input into a unified standard network virtual terminal format, and then transmits it to the remote server through the network in the form of TCP datagram. The server program converts the information in the network virtual terminal format into the local server operating system format.

The server provides the corresponding service according to the user's request, and finally returns the execution result to the client program in the same process, which converts it into the client format and displays it on the user's screen.

Through the shielding effect of the network virtual terminal, the interoperability between heterogeneous operating systems can be realized, and the consistency of the network can be realized again at the high level of the network. Corresponding to the network virtual terminal, IP protocol realizes the consistency of physical network at the lower level of the network.

Refer to the above contents: Baidu Encyclopedia -VTN, Baidu Encyclopedia-Network Virtual Terminal.