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24854a1c KM |
1 | .\" Copyright (c) 1983 Regents of the University of California. |
2 | .\" All rights reserved. The Berkeley software License Agreement | |
3 | .\" specifies the terms and conditions for redistribution. | |
4 | .\" | |
58ad5548 | 5 | .\" @(#)telnet.1 6.5 (Berkeley) %G% |
24854a1c | 6 | .\" |
12f553b7 | 7 | .TH TELNET 1C "" |
24854a1c KM |
8 | .UC 5 |
9 | .SH NAME | |
58ad5548 | 10 | telnet \- user interface to the \s-1TELNET\s0 protocol |
24854a1c KM |
11 | .SH SYNOPSIS |
12 | telnet [ host [ port ] ] | |
13 | .SH DESCRIPTION | |
14 | .I Telnet | |
5c2bded5 GM |
15 | is used to communicate with another host using the |
16 | .B TELNET | |
17 | protocol. | |
18 | If | |
24854a1c KM |
19 | .I telnet |
20 | is invoked without arguments, it enters command mode, | |
21 | indicated by its prompt (\*(lqtelnet>\*(rq). | |
22 | In this mode, it accepts and executes the commands listed below. | |
23 | If it is invoked with arguments, it performs an | |
5c2bded5 | 24 | .B open |
24854a1c KM |
25 | command (see below) with those arguments. |
26 | .PP | |
27 | Once a connection has been opened, | |
28 | .I telnet | |
5c2bded5 GM |
29 | enters an input mode. |
30 | The input mode entered will be either \*(lqcharacter at a time\*(rq | |
31 | or \*(lqline by line\*(rq | |
32 | depending on what the remote system supports. | |
33 | .PP | |
34 | In \*(lqcharacter at a time\*(rq mode, most | |
35 | text typed is immediately sent to the remote host for processing. | |
36 | .PP | |
37 | In \*(lqline by line\*(rq mode, all text is echoed locally, | |
38 | and (normally) only completed lines are sent to the remote host. | |
39 | The \*(lqlocal echo character\*(rq (initially \*(lq^E\*(rq) may be used | |
40 | to turn off and on the local echo | |
41 | (this would mostly be used to enter passwords | |
42 | without the password being echoed). | |
43 | .PP | |
44 | In either mode, if the | |
45 | .I localchars | |
349a83e1 | 46 | toggle is TRUE (the default in line mode; see below), |
5c2bded5 GM |
47 | the user's |
48 | .IR quit , | |
49 | .IR intr , | |
50 | and | |
51 | .I flush | |
52 | characters are trapped locally, and sent as | |
53 | .B TELNET | |
54 | protocol sequences to the remote side. | |
55 | There are options (see | |
56 | .B toggle | |
57 | .I autoflush | |
58 | and | |
59 | .B toggle | |
60 | .I autosynch | |
61 | below) | |
62 | which cause this action to flush subsequent output to the terminal | |
63 | (until the remote host acknowledges the | |
64 | .B TELNET | |
65 | sequence) and flush previous terminal input | |
66 | (in the case of | |
67 | .I quit | |
68 | and | |
69 | .IR intr ). | |
70 | .PP | |
71 | While connected to a remote host, | |
24854a1c | 72 | .I telnet |
5c2bded5 | 73 | command mode may be entered by typing the |
24854a1c | 74 | .I telnet |
12f553b7 | 75 | \*(lqescape character\*(rq (initially \*(lq^]\*(rq). |
24854a1c KM |
76 | When in command mode, the normal terminal editing conventions are available. |
77 | .PP | |
5c2bded5 GM |
78 | .B COMMANDS |
79 | .PP | |
24854a1c | 80 | The following commands are available. |
5c2bded5 GM |
81 | Only enough of each command to uniquely identify it need be typed |
82 | (this is also true for arguments to the | |
83 | .BR mode , | |
84 | .BR set , | |
85 | .BR toggle , | |
86 | and | |
87 | .B display | |
88 | commands). | |
24854a1c KM |
89 | .PP |
90 | .TP | |
5c2bded5 GM |
91 | .B open \fIhost\fP \fR[\fP \fIport\fP \fR]\fP |
92 | .br | |
93 | Open a connection to the named host. | |
94 | If no port number | |
24854a1c KM |
95 | is specified, |
96 | .I telnet | |
5c2bded5 GM |
97 | will attempt to contact a |
98 | .B TELNET | |
99 | server at the default port. | |
24854a1c KM |
100 | The host specification may be either a host name (see |
101 | .IR hosts (5)) | |
5c2bded5 GM |
102 | or an Internet address specified in the \*(lqdot notation\*(rq (see |
103 | .IR inet (3N)). | |
24854a1c KM |
104 | .TP |
105 | .B close | |
5c2bded5 GM |
106 | .br |
107 | Close a | |
108 | .B TELNET | |
109 | session and return to command mode. | |
24854a1c KM |
110 | .TP |
111 | .B quit | |
5c2bded5 GM |
112 | .br |
113 | Close any open | |
114 | .B TELNET | |
115 | session and exit | |
24854a1c | 116 | .IR telnet . |
3c604e97 | 117 | An end of file (in command mode) will also close a session and exit. |
24854a1c KM |
118 | .TP |
119 | .B z | |
5c2bded5 | 120 | .br |
24854a1c KM |
121 | Suspend |
122 | .IR telnet . | |
123 | This command only works when the user is using the | |
124 | .IR csh (1). | |
125 | .TP | |
5c2bded5 GM |
126 | .B mode \fItype\fP |
127 | .br | |
128 | .I Type | |
129 | is either | |
130 | .I line | |
131 | (for \*(lqline by line\*(rq mode) | |
132 | or | |
133 | .I character | |
134 | (for \*(lqcharacter at a time\*(rq mode). | |
135 | The remote host is asked for permission to go into the requested mode. | |
136 | If the remote host is capable of entering that mode, the requested | |
137 | mode will be entered. | |
24854a1c KM |
138 | .TP |
139 | .B status | |
5c2bded5 | 140 | .br |
24854a1c KM |
141 | Show the current status of |
142 | .IR telnet . | |
143 | This includes the peer one is connected to, as well | |
5c2bded5 GM |
144 | as the current mode. |
145 | .TP | |
146 | .B display \fR[\fP \fIargument...\fP \fR]\fP | |
147 | .br | |
148 | Displays all, or some, of the | |
149 | .B set | |
150 | and | |
151 | .B toggle | |
152 | values (see below). | |
153 | .TP | |
154 | .B ? \fR[\fP \fIcommand\fP \fR]\fP | |
155 | .br | |
24854a1c KM |
156 | Get help. With no arguments, |
157 | .I telnet | |
158 | prints a help summary. | |
159 | If a command is specified, | |
160 | .I telnet | |
5c2bded5 GM |
161 | will print the help information for just that command. |
162 | .TP | |
163 | .B send \fIarguments\fP | |
164 | .br | |
165 | Sends one or more special character sequences to the remote host. | |
166 | The following are the arguments which may be specified | |
167 | (more than one argument may be specified at a time): | |
168 | .RS | |
169 | .TP | |
170 | .I escape | |
171 | .br | |
172 | Sends the current | |
173 | .I telnet | |
174 | escape character (initially \*(lq^]\*(rq). | |
175 | .TP | |
176 | .I synch | |
177 | .br | |
178 | Sends the | |
179 | .B TELNET SYNCH | |
180 | sequence. | |
181 | This sequence causes the remote system to discard all previously typed | |
182 | (but not yet read) input. | |
183 | This sequence is sent as TCP urgent | |
184 | data (and may not work if the remote system is a 4.2 BSD system -- if | |
185 | it doesn't work, a lower case \*(lqr\*(rq may be echoed on the terminal). | |
186 | .TP | |
187 | .I brk | |
188 | .br | |
189 | Sends the | |
190 | .B TELNET BRK | |
191 | (Break) sequence, which may have significance to the remote | |
192 | system. | |
193 | .TP | |
194 | .I ip | |
195 | .br | |
196 | Sends the | |
197 | .B TELNET IP | |
349a83e1 | 198 | (Interrupt Process) sequence, which should cause the remote |
5c2bded5 GM |
199 | system to abort the currently running process. |
200 | .TP | |
201 | .I ao | |
202 | .br | |
203 | Sends the | |
204 | .B TELNET AO | |
205 | (Abort Output) sequence, which should cause the remote system to flush | |
206 | all output | |
207 | .B from | |
208 | the remote system | |
209 | .B to | |
210 | the user's terminal. | |
211 | .TP | |
212 | .I ayt | |
213 | .br | |
214 | Sends the | |
215 | .B TELNET AYT | |
216 | (Are You There) | |
349a83e1 | 217 | sequence, to which the remote system may or may not choose to respond. |
5c2bded5 GM |
218 | .TP |
219 | .I ec | |
220 | .br | |
221 | Sends the | |
222 | .B TELNET EC | |
223 | (Erase Character) | |
224 | sequence, which should cause the remote system to erase the last character | |
225 | entered. | |
226 | .TP | |
227 | .I el | |
228 | .br | |
229 | Sends the | |
230 | .B TELNET EL | |
231 | (Erase Line) | |
232 | sequence, which should cause the remote system to erase the line currently | |
233 | being entered. | |
234 | .TP | |
235 | .I ga | |
236 | .br | |
237 | Sends the | |
238 | .B TELNET GA | |
239 | (Go Ahead) | |
240 | sequence, which likely has no significance to the remote system. | |
241 | .TP | |
242 | .I nop | |
243 | .br | |
244 | Sends the | |
245 | .B TELNET NOP | |
246 | (No OPeration) | |
247 | sequence. | |
248 | .TP | |
249 | .I ? | |
250 | .br | |
251 | Prints out help information for the | |
252 | .B send | |
253 | command. | |
254 | .RE | |
255 | .TP | |
256 | .B set \fIargument value\fP | |
257 | .br | |
258 | Set any one of a number of | |
259 | .I telnet | |
260 | variables to a specific value. | |
261 | The special value \*(lqoff\*(rq turns off the function associated with | |
262 | the variable. | |
349a83e1 MK |
263 | The values of variables may be interrogated with the |
264 | .B display | |
265 | command. | |
5c2bded5 GM |
266 | The variables which may be specified are: |
267 | .RS | |
268 | .TP | |
269 | .I echo | |
270 | .br | |
271 | This is the value (initially \*(lq^E\*(rq) which, when in | |
272 | \*(lqline by line\*(rq mode, toggles between doing local echoing | |
273 | of entered characters (for normal processing), and suppressing | |
274 | echoing of entered characters (for entering, say, a password). | |
275 | .TP | |
276 | .I escape | |
277 | .br | |
278 | This is the | |
279 | .I telnet | |
280 | escape character (initially \*(lq^[\*(rq) which causes entry | |
281 | into | |
282 | .I telnet | |
283 | command mode (when connected to a remote system). | |
284 | .TP | |
285 | .I interrupt | |
286 | .br | |
287 | If | |
288 | .I telnet | |
289 | is in | |
290 | .I localchars | |
291 | mode (see | |
292 | .B toggle | |
293 | .I localchars | |
294 | below) | |
295 | and the | |
296 | .I interrupt | |
297 | character is typed, a | |
298 | .B TELNET IP | |
299 | sequence (see | |
300 | .B send | |
301 | .I ip | |
302 | above) | |
303 | is sent to the remote host. | |
304 | The initial value for the interrupt character is taken to be | |
305 | the terminal's | |
306 | .B intr | |
307 | character. | |
308 | .TP | |
309 | .I quit | |
310 | .br | |
311 | If | |
312 | .I telnet | |
313 | is in | |
314 | .I localchars | |
315 | mode (see | |
316 | .B toggle | |
317 | .I localchars | |
318 | below) | |
319 | and the | |
320 | .I quit | |
321 | character is typed, a | |
322 | .B TELNET BRK | |
323 | sequence (see | |
324 | .B send | |
325 | .I brk | |
326 | above) | |
327 | is sent to the remote host. | |
328 | The initial value for the quit character is taken to be | |
329 | the terminal's | |
330 | .B quit | |
331 | character. | |
332 | .TP | |
333 | .I flushoutput | |
334 | .br | |
335 | If | |
336 | .I telnet | |
337 | is in | |
338 | .I localchars | |
339 | mode (see | |
340 | .B toggle | |
341 | .I localchars | |
342 | below) | |
343 | and the | |
344 | .I flushoutput | |
345 | character is typed, a | |
346 | .B TELNET AO | |
347 | sequence (see | |
348 | .B send | |
349 | .I ao | |
350 | above) | |
351 | is sent to the remote host. | |
352 | The initial value for the flush character is taken to be | |
353 | the terminal's | |
354 | .B flush | |
355 | character. | |
356 | .TP | |
357 | .I erase | |
358 | .br | |
359 | If | |
360 | .I telnet | |
361 | is in | |
362 | .I localchars | |
363 | mode (see | |
364 | .B toggle | |
365 | .I localchars | |
366 | below), | |
367 | .B and | |
368 | if | |
369 | .I telnet | |
370 | is operating in \*(lqcharacter at a time\*(rq mode, then when this | |
371 | character is typed, a | |
372 | .B TELNET EC | |
373 | sequence (see | |
374 | .B send | |
375 | .I ec | |
376 | above) | |
377 | is sent to the remote system. | |
378 | The initial value for the erase character is taken to be | |
379 | the terminal's | |
380 | .B erase | |
381 | character. | |
382 | .TP | |
383 | .I kill | |
384 | .br | |
385 | If | |
386 | .I telnet | |
387 | is in | |
388 | .I localchars | |
389 | mode (see | |
390 | .B toggle | |
391 | .I localchars | |
392 | below), | |
393 | .B and | |
394 | if | |
395 | .I telnet | |
396 | is operating in \*(lqcharacter at a time\*(rq mode, then when this | |
397 | character is typed, a | |
398 | .B TELNET EL | |
399 | sequence (see | |
400 | .B send | |
401 | .I el | |
402 | above) | |
403 | is sent to the remote system. | |
404 | The initial value for the kill character is taken to be | |
405 | the terminal's | |
406 | .B kill | |
407 | character. | |
408 | .TP | |
409 | .I eof | |
410 | .br | |
411 | If | |
412 | .I telnet | |
413 | is operating in \*(lqline by line\*(rq mode, entering this character | |
414 | as the first character on a line will cause this character to be | |
415 | sent to the remote system. | |
416 | The initial value of the eof character is taken to be the terminal's | |
417 | .B eof | |
418 | character. | |
419 | .RE | |
420 | .TP | |
421 | .B toggle \fIarguments...\fP | |
422 | .br | |
423 | Toggle (between | |
424 | TRUE | |
425 | and | |
426 | FALSE) | |
427 | various flags that control how | |
428 | .I telnet | |
429 | responds to events. | |
430 | More than one argument may be specified. | |
349a83e1 MK |
431 | The state of these flags may be interrogated with the |
432 | .B display | |
433 | command. | |
5c2bded5 GM |
434 | Valid arguments are: |
435 | .RS | |
436 | .TP | |
437 | .I localchars | |
438 | .br | |
439 | If this is | |
440 | TRUE, | |
441 | then the | |
442 | .IR flush , | |
443 | .IR interrupt , | |
444 | .IR quit , | |
445 | .IR erase , | |
446 | and | |
447 | .I kill | |
448 | characters (see | |
449 | .B set | |
450 | above) are recognized locally, and transformed into (hopefully) appropriate | |
451 | .B TELNET | |
452 | control sequences | |
453 | (respectively | |
454 | .IR ao , | |
455 | .IR ip , | |
456 | .IR brk , | |
457 | .IR ec , | |
458 | and | |
459 | .IR el ; | |
460 | see | |
461 | .B send | |
462 | above). | |
463 | The initial value for this toggle is TRUE in \*(lqline by line\*(rq mode, | |
464 | and FALSE in \*(lqcharacter at a time\*(rq mode. | |
465 | .TP | |
5c2bded5 GM |
466 | .I autoflush |
467 | .br | |
468 | If | |
469 | .I autoflush | |
470 | and | |
471 | .I localchars | |
472 | are both | |
473 | TRUE, | |
474 | then when the | |
475 | .IR ao , | |
476 | .IR intr , | |
477 | or | |
478 | .I quit | |
479 | characters are recognized (and transformed into | |
480 | .B TELNET | |
481 | sequences; see | |
482 | .B set | |
483 | above for details), | |
484 | .I telnet | |
485 | refuses to display any data on the user's terminal | |
486 | until the remote system acknowledges (via a | |
487 | .B TELNET | |
488 | .I Timing Mark | |
489 | option) | |
490 | that it has processed those | |
491 | .B TELNET | |
492 | sequences. | |
493 | The initial value for this toggle is TRUE if the terminal user had not | |
494 | done an "stty noflsh", otherwise FALSE (see | |
495 | .IR stty(1)). | |
496 | .TP | |
349a83e1 MK |
497 | .I autosynch |
498 | If | |
499 | .I autosynch | |
500 | and | |
501 | .I localchars | |
502 | are both | |
503 | TRUE, | |
504 | then when either the | |
505 | .I intr | |
506 | or | |
507 | .I quit | |
508 | characters is typed (see | |
509 | .B set | |
510 | above for descriptions of the | |
511 | .I intr | |
512 | and | |
513 | .I quit | |
514 | characters), the resulting | |
515 | .B TELNET | |
516 | sequence sent is followed by the | |
517 | .B TELNET SYNCH | |
518 | sequence. | |
519 | This procedure | |
520 | .B should | |
521 | cause the remote system to begin throwing away all previously | |
522 | typed input until both of the | |
523 | .B TELNET | |
524 | sequences have been read and acted upon. | |
525 | The initial value of this toggle is FALSE. | |
526 | .TP | |
5c2bded5 GM |
527 | .I crmod |
528 | .br | |
529 | Toggle carriage return mode. | |
530 | When this mode is enabled, most carriage return characters received from | |
531 | the remote host will be mapped into a carriage return followed by | |
532 | a line feed. | |
533 | This mode does not affect those characters typed by the user, only | |
534 | those received from the remote host. | |
535 | This mode is not very useful unless the remote host | |
536 | only sends carriage return, but never line feed. | |
537 | The initial value for this toggle is FALSE. | |
538 | .TP | |
539 | .I debug | |
540 | .br | |
541 | Toggles socket level debugging (useful only to the | |
542 | .IR super user ). | |
543 | The initial value for this toggle is FALSE. | |
544 | .TP | |
545 | .I options | |
546 | .br | |
547 | Toggles the display of some internal | |
548 | .I telnet | |
549 | protocol processing (having to do with | |
550 | .B TELNET | |
551 | options). | |
552 | The initial value for this toggle is FALSE. | |
553 | .TP | |
554 | .I netdata | |
555 | .br | |
556 | Toggles the display of all network data (in hexadecimal format). | |
557 | The initial value for this toggle is FALSE. | |
558 | .TP | |
559 | .I ? | |
560 | .br | |
561 | Displays the legal | |
562 | .B toggle | |
563 | commands. | |
564 | .RE | |
24854a1c | 565 | .SH BUGS |
5c2bded5 GM |
566 | .PP |
567 | There is no adequate way for dealing with flow control. | |
568 | .PP | |
569 | On some remote systems, echo has to be turned off manually when in | |
570 | \*(lqline by line\*(rq mode. | |
571 | .PP | |
572 | There is enough settable state to justify a | |
573 | .RI . telnetrc | |
574 | file. | |
575 | .PP | |
576 | No capability for a | |
577 | .RI . telnetrc | |
578 | file is provided. | |
579 | .PP | |
580 | In \*(lqline by line\*(rq mode, the terminal's | |
581 | .I eof | |
582 | character is only recognized (and sent to the remote system) | |
583 | when it is the first character on a line. |