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Remote log-in with Telnet.

Remote Log-in with Telnet

Last month's column discussed file transfer on the Internet using File Transfer Protocol (FTP). Another fundamental TCP/IP application for Internet use is remote log-in.

Remote log-in is a basic interactive resource sharing service. It enables users to connect to any machine on the Internet and conduct a session as if they were directly attached to the remote system. Telnet is the standard TCP/IP remote log-in protocol.

Just like FTP, Telnet can be used to connect to a system where you have an account or to any system that allows remote connection from anonymous users. This enables you to access all kinds of services and resources available on other computer systems. These range from campus wide information systems (CWIS), library catalogs, full-text databases, bulletin boards systems, and even weather forecasts.

These resources run on everything from personal computers and workstations to minicomputers and mainframes. When you consider the countless makes and models of dissimilar computers on the Internet, each with its own particular settings and parameters, you might think connecting would be a nightmare.

Users of personal computer communications software are well acquainted with the problems in getting two computers to communicate. A remote system, whether it be the campus mainframe, another PC, or a commercial system such as CompuServe or DIALOG, requires the right settings before communication can be established. Baud rate, data and parity bits, duplex, flow control, and terminal emulation are just a few of the parameters that must be correctly matched. Telnet handles the problem of settings transparently by using a virtual terminal interface in which the local and remote computers handle all the details.

Virtual Terminals

The central component of Telnet is a character-oriented device called a Network Virtual Terminal consisting of two modules, User Telnet and Server Telnet. User Telnet interacts with the terminal input/output module to communicate with a local terminal. It converts the characteristics of real terminals to the network-standard virtual terminals and vice versa. Server Telnet interacts with an application, acting as a surrogate terminal handler, so that remote terminals appear as local to the application program.

The user initiates a session to a remote system from a local terminal, and a server awaits or listens for a connection from a remote user. Telnet allows users or servers to request or respond to option settings, although most Telnet sessions choose to operate in an ASCII full-duplex mode. This makes it possible for any dumb ASCII terminal to access remote systems, although Telnet has options to support other types of data streams, such as the transmission of 3270 data when communicating with IBM equipment.

Thankfully, the user can remain blissfully unaware of these technical details and just use the program. In this respect Telnet is easier to use than standard communications programs such as Crosstalk or Smartcom, as it requires no fiddling with parameters when making a connection.

Using Telnet

Telnet is basically a communications program that runs over TCP/IP, and, like most applications, there are a number of versions. Many UNIX systems include Telnet as part of the operating system. There are a number of vendors supplying Telnet for large VAX or IBM systems, as well as implementations for personal computers. There are even public domain and shareware versions for MS-DOS, Windows 3.0, and the Macintosh. While each version of Telnet has certain features, the basic operations are similar.

To connect to another computer, run Telnet and supply the address of the remote system (see Figure 1). The address is usually an Internet domain name. For example, is the address of the Colorado Research Libraries network. Some versions of Telnet cannot use Internet domain names and require the actual IP numeric address. Using such a program requires you to know that is the IP address for CARL. To find an IP number when the domain name is known, consult The User's Directory of Computer Networks by Tracey LaQuey.

Once a connection is established, what happens next depends on the remote system. In the case of anonymous log-ins the server Telnet program can be linked to an application program so that the remote user is automatically placed in the program. This is a good way to make OPACs available.

Other systems have the remote user enter commands or select from a menu of services. Once connected you must know the commands used by the interface on the remote service. This can be a real problem when connecting to unfamiliar programs such as library OPACs.

If you find Telnet rather primitive and spartan, there are some options. Users of personal computers can use a communications program that supports TCP/IP such as the new version 3.11 of Kermit. Macintosh users can use Telnet Driver from InterCon Systems. This product provides TCP/IP capabilities to several popular Macintosh serial communication programs. It enables them to communicate with a remote system over a virtual terminal connection as if they were connected by a serial line. Users would probably prefer using a familiar program for all communications sessions instead of using different ones for serial and TCP/IP sessions.

Terminal Problems

In the old days when everyone used terminal programs that asked you to press PF12 or the Gold key, there were few problems, as those were actual keys on the keyboard. Most programs running on large computer systems still assume the use of one kind of terminal or another. This is particularly true of many OPACs.

But the extensive use of personal computers has caused a few problems in that the keys are different. Most communications programs provide key mapping by translating terminal keys to the personal computer keyboard. For example, when ProComm emulates a VT-100 terminal, it uses F1 as the PF1 key, shifted F10 as the Enter key, and shift F4 as the keypad dash key.

The same problem exists with Telnet, which, depending on the type of remote system, uses two types of terminal emulation. The usual mode of operation is the DEC VT-100. When connected to IBM 370-type computers, 3270 emulation is used.

Many versions of Telnet set the terminal emulation automatically upon connection, although some allow this to be negotiated. Programs written for IBM 3270 dedicated terminals seem to make extensive use of function keys which must be mapped to the existing keyboard. The results can be difficult to use, although some versions of Telnet allow you to customize the keys to your liking.

Another problem is that some server programs require connection to a particular port. For example, the University of Michigan's weather server ( requires you to connect to port 3000 and the method of doing this seems to vary with each version of Telnet. Finally, some programs, including OPACs, assume you are using a directly connected terminal and provide no way to exit the program.

Telnet provides a way of sending escape sequences that can be used to break the connection to a remote computer, but each version of Telnet seems to use a different key, from ALT-X to CTRL-Q to F10. Consult the documentation for your particular version. Once you are familiar with the nuances of Telnet, you are ready to try some of the services on net.

Available Services

One of the biggest obstacles to using the Internet is finding out what services are available. Billy Barron at the University of North Texas produces UNT's "Accessing On-Line Bibliographic Databases," which not only lists library OPACs on the Internet (along with some databases), but also provides details on using the various library systems and even an appendix of Telnet escape sequences.

This invaluable document is available for anonymous FTP from in the LIBRARIES directory. WordPerfect 5.1, PostScript, and ASCII formats are available. The same site also contains Art St. George's list of "Internet-Accessible Library Catalogues & Databases." For a list of Canadian libraries, retrieve the file CDN_INTERNET_LIBS.TXT from in the LIBSOFT directory.

Besides library OPACs and databases, there are also many bulletin board systems on the Internet. A list of available systems is in the file INTERNET_BBS.TXT at LIBSOFT and a list of campuswide information services (WAIS) is in the file WAIS.TXT in the same directory. These lists should provide enough information to get you started.

Future Trends

The character-oriented design of Telnet limits it to character-based applications. Its long-term future is uncertain as most current program development is based on bit-mapped graphics systems such as Windows, Motif, or Open Desktop. And while the X-windows interface standard offers a way to use graphics across the Internet, its widespread adoption would require much faster connections for optimal response time and the increased data flow may overload existing links.

Even though the International Standards Organization has an improved Virtual Terminal specification, the final solution may be the implementation of a client/server model in which the interface resides on the local system. For the Internet to fulfill its promise of an information superhighway, some standards will have to be developed.

During the first generation of online information systems, we have struggled to learn dozens of different online and CD-ROM interfaces. For the information age to become a reality, the next generation of systems must separate the data from the interface. Some progress has been made in this area, and next month's column on full-text databases will fill in some more details. [Figure 1 Omitted]

Gord Nickerson is the information systems support officer at the School of Library and Information Science, Elborn College, University of Western Ontario.
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Title Annotation:Networked Resources; communications program
Author:Nickerson, Gord
Publication:Computers in Libraries
Article Type:Evaluation
Date:Nov 1, 1991
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