Chapter 2 Virtual Terminal

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In order to issue interactive commands to a remote operating system or to a subsystem available on a remote computer, you must establish a session on the remote node. The Virtual Terminal service (VT) makes the fact that the session is remote almost entirely transparent. You enter commands and receive system/subsystem responses at your local terminal just as if your session were local. When you edit text in a remote editor subsystem, the text appears in the proper format on your local terminal screen. In reality, input and output to your local terminal pass through a "virtual" (as opposed to actual, physical) terminal configured on the remote system. Your remote commands are transmitted over network connections, sent to the virtual terminal, and subsequently executed on the remote system.

Using the Virtual Terminal service, you can take advantage of a remote system's processing capabilities. For example, if a program needs to be run on a remote node, you can use VT to access it, edit the program, and then compile, load, and run it directly on the remote node.

The Reverse Virtual Terminal service enables an application process within a node to communicate with a real terminal that is on its network or internetwork. The application's home node sets up a virtual terminal for each real terminal that the application needs access to. Information sent from a terminal to the application process (or vice versa) passes through the appropriate virtual terminal. With Reverse VT, the application process can accept input from all nodes, though individual sessions are not established on each node.

Figure 2-1 “Virtual Terminal Service” is a schematic illustration of the Virtual Terminal (and Reverse Virtual Terminal) service. By using the NS 3000/iX Virtual Terminal service on a network, you can log on to any session-accepting node in the network from your own local node. All systems are transparently accessible to each other.

Figure 2-1 Virtual Terminal Service

In addition to your local session, you can also create multiple remote sessions on your own local node or on remote nodes. Optionally, you can configure your own remote prompts, so that you can identify each remote environment by its prompt.

In order to create a remote session, you can use either REMOTE :nodename followed by a logon, or, you can use DSLINE nodename followed by a REMOTE HELLO user.acct. After using either the DSLINE command or the REMOTE HELLO command, you then use the REMOTE command in order to be able to use commands in the remote environment. The following pages will explain how to use these commands.

For recommended programming practices for VT-connected devices, refer to the Asynchronous Serial Communications Programmer's Reference Manual.

Chapter 2 Virtual Terminal

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