Overview

Terminal access enables a terminal to use an asynchronous interface to access a front-end processor (FEP) or another terminal through a router.

The following types of network devices are used in terminal access:

• Terminal—A character device that is generally connected to another device through a serial interface cable. A user inputs characters by using the terminal keyboard. Then the characters are transferred to another device through the serial interface cable. After processing the characters, the device returns the result to the terminal, which displays the result on its screen.

• Initiator—Sends a connection request and serves as the client of the connection. Generally, a router is used as an initiator

• Receiver—Responds to a connection request and serves as the server of the connection. A receiver can be an FEP or a router. An FEP is a system installed with an application program for banking, postal service, taxation, customs, civil aviation, and so on. A FEP can be a Unix server or a Linux server.

• Relay server—Provides similar functions as a receiver, except that the relay server is not directly connected to terminals. Instead, the relay server is connected to multiple initiators simultaneously and manages them in different forwarding groups according to the listening port number. Data received from an initiator is forwarded to other initiators in the same group.

After a connection is established, the router, functioning as either the terminal access initiator or receiver, can transparently transmit the data from the terminal to the peer over the connection. Transparent means that no manual or extra operation is required.

Connections between an initiator and a receiver can use either TCP or UDP.