Tuesday, May 27, 2008

Terminal Emulation

Terminal emulation is a way to make your Windows PC look like a simple asynchronous terminal. Using your Windows PC as a terminal is a simple way to allow you to connect to a UNIX machine. You can then input commands from your PC’s keyboard and receive output display on your PC screen. Microsoft provides two built-in terminal emulators, HyperTerminal (for dial-up connections) and the telnet client (for direct LAN connections). In addition, there are a number of third-party software packages that provide terminal emulation services on Windows machines.

Logging In to Your UNIX System from Your PC

A simple way to use DOS and the UNIX System together is to treat them as two distinct systems, and to simply access the UNIX System from your personal computer using a terminal emulation program to turn your PC into a UNIX System terminal. You can run whatever programs are important to you in a Windows environment and turn your personal computer into a UNIX System terminal when you wish to log in to your UNIX System.

When you run a terminal emulator, your personal computer becomes a virtual terminal. You do not have access to most features of Windows and cannot run most Windows application programs while using the emulator without escaping the emulator environment and going back to Windows. However, you can run selected commands that manipulate files, like COPY, RENAME, and ERASE. These commands are usually preceded by some command to let the emulator recognize it as a DOS command.

You can also do simple file transfers. Most terminal emulators have features that allow you to upload files to your UNIX system from the personal computer, and to download files from your UNIX system to your personal computer. Numerous terminal emulators are available for Windows machines, some of which come packaged together with an operating system environment. The next section briefly discusses the use of telnet, Dial-Up Networking, and an example of a commercially available product called NetTerm as ways to access UNIX machines.

Microsoft Windows Terminal Emulators

To access your UNIX machine, you need to establish a connection between your PC and the UNIX machine you want to connect to. The type of connection you establish depends on whether you are on a LAN (local area network), or remote (not directly connected). Microsoft has implemented both ways of accessing remote computers, including UNIX machines, as part of its environment. In particular, Microsoft includes a built-in telnet function for connecting to another machine over a LAN and a service called Dial-Up Networking for connecting over a phone line. Both of these are discussed in the next sections.

The Microsoft terminal emulation programs lack some important features, so other vendors, such as InterSoft International, have created third-party applications that run as terminal emulators on Windows machines, such as NetTerm, which provide richer feature sets than the standard Microsoft software.

Using telnet to Access Your UNIX System

The telnet application allows you to connect one machine to another machine using the TCP/IP protocol, regardless of the operating systems on the machines.

If you are connected to a LAN, you can access a UNIX machine simply by using the built-in telnet application on your Windows machine. There are three ways to access the program. The first is to use your Start bar and select the Run icon. You can then type in a command such as:


which will open up a telnet connection to the UNIX machine at that address on your LAN. If you have a DNS name for the machine you can alternatively type its name, for example, to connect to the machine named hoviserve:

telnet hoviserve

Another way is to access telnet via your web browser. Selecting a URL that begins with the string “telnet://” displays the same telnet session window as in the previous two methods.

Once you have opened up the telnet session, you log in to your UNIX machine by supplying your login ID and password as normal.

Using Dial-Up Networking to Access Your UNIX System

If you are accessing your UNIX system remotely (not on a LAN), you need to establish a dial-up connection. Windows has a feature called Dial-Up Networking that allows you to do this. To set up an icon to allow you to connect to a UNIX machine, you need to know a few things ahead of time. You need to know the dial-up number for the system you want to access, and some information about where you are calling from and what type of phone service you have (for instance, does it include call waiting). You also need to know what speed modem you are using, and which COM port it is connected to. After selecting the Network and Dial-up Connections header from the ones available under My Computer, you complete the information

fields on the pop-up window (note that this is the same function as HyperTerminal). When they are complete, you are asked to save the configuration in a file. You should give the file a unique name, one that describes the UNIX system to which this information pertains, such as the computer name (for instance, flipper, if your UNIX machine name is flipper). You should then move this file to your desktop, so that it is available for use without your having to hunt for it.

To connect to a UNIX system from your Windows environment, select the Dial-Up Networking icon that is associated with that particular system (you may have multiple icons and multiple configuration settings for each UNIX system that you connect to) and use the pop-up windows that appear to automatically dial for you. Once you are connected, go through the usual UNIX System login procedure.

Using Packages Such as NetTerm to Access Your UNIX System

Third-party applications perform the same basic connecting functions as the built-in Microsoft ones but provide more flexibility in configuration and options that are not available with the Microsoft telnet implementation. One such package is NetTerm, by InterSoft International. NetTerm allows you to create and maintain a phone directory of many machines, each of which may have different characteristics. For instance, you can configure your desktop look (number of lines, number of lines to scroll, line width, and so on). You can also configure the keyboard mappings. This is especially useful if you want to use keys that are not part of the standard ones you normally use in typing.

Once you have such a package installed and configured, you can store it on your desktop so that it can be run by double-clicking the associated icon.

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