TELNET tipsThe Telnet protocol has been implemented on a variety of systems. Eachis different, so specific commands depend on your version. However, allversions function similarly, so there are a few general guidelines tofollow.The one common element across the disparate environments of the Internetis the TCP/IP software protocol suite, the basis of communications.Telnet, the terminal-handler portion of the TCP/IP protocol suite, isthe cornerstone of this striking communications technology. Telnethandles the remote login to another Internet host, so it is useful toknow something about the way it works.Telnet operates in a client/server environment in which one host (thecomputer you are using, running Client (User) Telnet) negotiates openinga session on another computer (the remote host, running Server Telnet).During the behind-the-scenes negotiation process, the two computersagree on the parameters governing the session. One of the first thingsthey settle is the terminal type to be used -- in general, aline-by-line network virtual terminal, for simplicity's sake. Virtualterminal, in this context, refers to a set of terminal characteristicsand sequences that both sides of a network connection agree to use totransmit data from terminals across the network, regardless of theterminal used. Finding Telnet CommandsTry typing "help" or "?" at the Telnet prompt to get a list of thecommands available in your Telnet software. Using Local versus Remote CommandsOnce you have established a remote session, all commands you type willbe sent to the Server Telnet on the remote host for execution.If you want a Telnet command issued in the remote environment to beacted on locally by your client Telnet, on most systems you wouldnormally precede the command with an escape sequence (a predeterminedcharacter or combination of characters that signal your Telnet softwareto execute the command that follows locally). For example, in NCSATelnet for pc-compatible microcomputers, the F10 key is the escapecharacter that alerts Telnet to execute locally the next command youtype (to turn local echo on or off, or to toggle capture on or off,etc.).The Telnet escape sequence by itself followed by [cr] returns youtemporarily to your local operating environment. On UNIX systems, theescape sequence is usually the control key (CNTL) and left bracket ([)pressed simultaneously. Logging OnTELNET [host] orTELNET [cr] followed by OPEN [host] at the prompt.The basic command set is simple. You also need to know either themachine domain name or the machine Internet address (a series ofnumbers). The numbers will always work; the names will work if they arein a software table available to your version of Telnet.IBM systems that use TN3270 may require you to type a carriage return,"DIAL VTAM," or just "VTAM" in response to the first prompt from theremote system. Logging OffLOGOFF or LOGOUT (also try QUIT, END, EXIT, STOP, etc.)CLOSE, prefixed by the escape sequence.ABORT, prefixed by the escape sequence--use as a last resort!To exit the remote system, first try that system's logoff command. Todetermine what the appropriate logoff command is, check the menus, help,and welcome screens when you first log on. Oftentimes, the logoffinformation is listed there but not always easy to retrieve later.Logging off the remote system may return you to your primary operatingenvironment (all the way out of Telnet), or you may be left in Telnet.If so, type "quit".But some information systems have no graceful exit for remote users. Inthat case, you have two options --- CLOSE or ABORT.CLOSE should be your next choice after LOGOFF. If you are unable toCLOSE the connection normally (e.g., if your remote session is hung),try the Telnet ABORT command to drop your connection locally.ABORT will return control to you in your local environment, but it maynot properly terminate your session on the remote machine. Since thiscan leave the port on the remote machine busy for an indefinite periodeven though you are no longer using it, ABORT should be used only as alast resort.In either case, you can also try escaping back to your local environmentand then issuing the termination commands. If one method doesn't work,try the other.Other commands may allow you to control your communications environment.Investigate the help systems both in your local Telnet and on the remotesystem at the outset. Using the BREAK KeyDon't be hasty with the Break key. Too many Breaks may cause yourTelnet session to be dropped!There is no standard BREAK key across versions of Telnet and in remoteinformation systems. Telnet is based on the concept of a networkvirtual terminal, in which the control functions (breaks, etc.) arecommunicated with characters regardless of terminal type (rather thanline conditions, used in the terminal server environment). Your localTelnet receives your break and sends out a character sequence which isreinterpreted on the other end, hopefully as the break you intended.Your Break may not always be understood by the remote system, so youshould try HELP or ? when you begin (at the Telnet prompt) to determinewhat your version of Telnet uses as BREAK.Tips: In UNIX, CNTL-C may work for BREAK. In the Mac environment, BREAKmay be a click down menu option or a character combination. In NCSATelnet (a popular PC version), BREAK is F10 followed by a lower caseletter "b". Using the Backspace KeyThe backspace character may not be recognized by the remote system.Investigate in your local Telnet how to set an erasing backspace. Type? at the Telnet prompt, or SET ? for a list of possibilities. Adjusting the Settings to your NeedsMost Telnet programs have the ability to SET or TOGGLE many of thesesettings on and off. Erasable backspace, local echo, carriage returninterpretation ([cr] or [cr][lf] -- i.e., carriage return or carriagereturn with line feed), and the escape character you use to return tothe local environment are things that you can usually SET or TOGGLE atthe Telnet prompt. Type ? and use Telnet's internal help system tochange a setting. Using Function KeysRemember that special function keys are local implementations and haveno significance in a remote session. Function keys such as INSERT,DELETE, ERASE END-OF-FIELD, PF, and PA keys may not be recognized in theremote environment. Even though function keys and control keycombinations may have significance on the remote system, they may varyfrom those on your local system. Even though function keys and control key
combinations may have significance on the remote system, they may vary
