1. What are telnet and tn3270
2. Logging into a remote computer
3. Logging out of a remote computer
4. Additional commands

Telnet is a program that allows a user on one computer to establish an interactive session with another computer on a network. The two computers must be connected to the Internet. The tn3270 program is a telnet program used to connect to an IBM mainframe and emulate a 3270 terminal. You will use this program to connect to NERDC services. Use telnet to connect to NERDC NERSP, however.

Telnet has two parts: the client and the server. The telnet client is a program on the computer you are using or are logged into. The telnet server is a program on a remote computer that you want to connect to.

This handout describes the general capabilities of most telnet clients and servers. However, not all telnet programs are alike and you may find that the telnet client or the server you are connected to has slightly different behavior. In particular, the commands in this handout are presented in command line format, like that used on many large computers. IBM PC and Macintosh client software, such as HostExplorer or Macintosh Telnet, present a graphical, window-oriented interface. To use any telnet or tn3270 program, however, you must supply the hostname, that is, the Internet name for the computer you want to connect to.

On most large computers, type the telnet command to start the telnet client program or tn3270 to start the tn3270 client program:

telnet hostname

or

tn3270 hostname

The hostname is the computer you wish to connect to. For example, to connect to the CIRCA Grove computer type:

telnet grove.ufl.edu

If you are using a microcomputer, open the icon for the telnet software. You may have to select a command from the File menu to type in the hostname.

The telnet client program will start running and will connect you to the remote computer. You can log in as you normally would and use the remote computer.

When you are finished using the remote computer, log out of the system as you normally would. The telnet or tn3270 program will automatically finish running.

You can start the telnet or tn3270 program without automatically connecting to a remote computer. Type the telnet command or tn3270 command without a hostname:

telnet

or

tn3270

You will now see the telnet or tn3270 prompt:

telnet>

or

tn3270>

From this prompt you can use use the telnet or tn3270 commands that your particular client program provides. Most clients will allow you to log into and out of different remote computers without exiting the telnet program. This saves time since the telnet program only has to be loaded once. Another common feature is the ability to transfer files between your computer and the remote computer.

These commands differ from system to system. You will need to determine how they work on your system. Most clients will respond with a list of available commands if you enter help or a ? at the telnet or tn3270 prompt. For example:

telnet> ?