1TELNET(1) BSD General Commands Manual TELNET(1)
2
4 telnet — user interface to the TELNET protocol
5
7 telnet [-8EFKLacdfrx] [-X authtype] [-b hostalias] [-e escapechar]
8 [-k realm] [-l user] [-n tracefile] [host [port]]
9
11 The telnet command is used to communicate with another host using the
12 TELNET protocol. If telnet is invoked without the host argument, it
13 enters command mode, indicated by its prompt (telnet>). In this mode, it
14 accepts and executes the commands listed below. If it is invoked with
15 arguments, it performs an open command with those arguments.
16 The options are as follows:
18 -7 Strip 8th bit on input and output. Telnet is 8-bit clean by
20 default but doesn't send the TELNET BINARY option unless forced.
21 -8 Specifies an 8-bit data path. This causes an attempt to negoti‐
23 ate the TELNET BINARY option on both input and output.
24 -E Stops any character from being recognized as an escape character.
26 -F If Kerberos V5 authentication is being used, the -F option allows
28 the local credentials to be forwarded to the remote system,
29 including any credentials that have already been forwarded into
30 the local environment.
31 -K Specifies no automatic login to the remote system.
33 -L Specifies an 8-bit data path on output. This causes the BINARY
35 option to be negotiated on output.
36 -X atype
38 Disables the atype type of authentication.
39 -a Attempt automatic login. Currently, this sends the user name via
41 the USER variable of the ENVIRON option if supported by the
42 remote system. The name used is that of the current user as
43 returned by getlogin(2) if it agrees with the current user ID,
44 otherwise it is the name associated with the user ID.
45 -b hostalias
47 Uses bind(2) on the local socket to bind it to an aliased address
48 (see ifconfig(8) and the ``alias'' specifier) or to the address
49 of another interface than the one naturally chosen by connect(2).
50 This can be useful when connecting to services which use IP
51 addresses for authentication and reconfiguration of the server is
52 undesirable (or impossible).
53 -c Disables the reading of the user's .telnetrc file. (See the
55 toggle skiprc command on this man page.)
56 -d Sets the initial value of the debug toggle to TRUE.
58 -e escapechar
60 Sets the initial telnet escape character to escapechar. If
61 escapechar is omitted, then there will be no escape character.
62 -f If Kerberos V5 authentication is being used, the -f option allows
64 the local credentials to be forwarded to the remote system.
65 -k realm
67 If Kerberos authentication is being used, the -k option requests
68 that telnet obtain tickets for the remote host in realm realm
69 instead of the remote host's realm, as determined by
70 krb_realmofhost(3).
71 -l user
73 When connecting to the remote system, if the remote system under‐
74 stands the ENVIRON option, then user will be sent to the remote
75 system as the value for the variable USER. This option implies
76 the -a option. This option may also be used with the open com‐
77 mand.
78 -n tracefile
80 Opens tracefile for recording trace information. See the set
81 tracefile command below.
82 -r Specifies a user interface similar to rlogin(1). In this mode,
84 the escape character is set to the tilde (~) character, unless
85 modified by the -e option.
86 -x Turns on encryption of the data stream if possible.
88 host Indicates the official name, an alias, or the Internet address of
90 a remote host.
91 port Indicates a port number (address of an application). If a number
93 is not specified, the default telnet port is used.
94 When in rlogin mode, a line of the form ~. disconnects from the remote
96 host; ~ is the telnet escape character. Similarly, the line ~^Z suspends
97 the telnet session. The line ~^] escapes to the normal telnet escape
98 prompt.
99 Once a connection has been opened, telnet will attempt to enable the
101 TELNET LINEMODE option. If this fails, telnet will revert to one of two
102 input modes: either ``character at a time'' or ``old line by line''
103 depending on what the remote system supports.
104 When LINEMODE is enabled, character processing is done on the local sys‐
106 tem, under the control of the remote system. When input editing or char‐
107 acter echoing is to be disabled, the remote system will relay that infor‐
108 mation. The remote system will also relay changes to any special charac‐
109 ters that happen on the remote system, so that they can take effect on
110 the local system.
111 In ``character at a time'' mode, most text typed is immediately sent to
113 the remote host for processing.
114 In ``old line by line'' mode, all text is echoed locally, and (normally)
116 only completed lines are sent to the remote host. The ``local echo char‐
117 acter'' (initially ``^E'') may be used to turn off and on the local echo
118 (this would mostly be used to enter passwords without the password being
119 echoed).
120 If the LINEMODE option is enabled, or if the localchars toggle is TRUE
122 (the default for ``old line by line''; see below), the user's quit, intr,
123 and flush characters are trapped locally, and sent as TELNET protocol
124 sequences to the remote side. If LINEMODE has ever been enabled, then
125 the user's susp and eof are also sent as TELNET protocol sequences, and
126 quit is sent as a TELNET ABORT instead of BREAK. There are options (see
127 toggle autoflush and toggle autosynch below) which cause this action to
128 flush subsequent output to the terminal (until the remote host acknowl‐
129 edges the TELNET sequence) and flush previous terminal input (in the case
130 of quit and intr).
131 While connected to a remote host, telnet command mode may be entered by
133 typing the telnet ``escape character'' (initially ``^]''). When in com‐
134 mand mode, the normal terminal editing conventions are available. Note
135 that the escape character will return to the command mode of the initial
136 invocation of telnet that has the controlling terminal. Use the send
137 escape command to switch to command mode in subsequent telnet processes
138 on remote hosts.
139 The following telnet commands are available. Only enough of each command
141 to uniquely identify it need be typed (this is also true for arguments to
142 the mode, set, toggle, unset, slc, environ, and display commands).
143 auth argument [...]
145 The auth command manipulates the information sent through the
146 TELNET AUTHENTICATE option. Valid arguments for the auth com‐
147 mand are as follows:
148 disable type Disables the specified type of authentication.
150 To obtain a list of available types, use the
151 auth disable ? command.
152 enable type Enables the specified type of authentication.
154 To obtain a list of available types, use the
155 auth enable ? command.
156 status Lists the current status of the various types of
158 authentication.
159 close Close a TELNET session and return to command mode.
161 display argument [...]
163 Displays all, or some, of the set and toggle values (see
164 below).
165 encrypt argument [...]
167 The encrypt command manipulates the information sent through
168 the TELNET ENCRYPT option.
169 Valid arguments for the encrypt command are as follows:
171 disable type [input|output]
173 Disables the specified type of encryption. If
174 you omit input and output, both input and output
175 are disabled. To obtain a list of available
176 types, use the encrypt disable ? command.
177 enable type [input|output]
179 Enables the specified type of encryption. If
180 you omit input and output, both input and output
181 are enabled. To obtain a list of available
182 types, use the encrypt enable ? command.
183 input This is the same as the encrypt start input com‐
185 mand.
186 -input This is the same as the encrypt stop input com‐
188 mand.
189 output This is the same as the encrypt start output
191 command.
192 -output This is the same as the encrypt stop output com‐
194 mand.
195 start [input|output]
197 Attempts to start encryption. If you omit input
198 and output, both input and output are enabled.
199 To obtain a list of available types, use the
200 encrypt enable ? command.
201 status Lists the current status of encryption.
203 stop [input|output]
205 Stops encryption. If you omit input and output,
206 encryption is on both input and output.
207 type type Sets the default type of encryption to be used
209 with later encrypt start or encrypt stop com‐
210 mands.
211 environ arguments [...]
213 The environ command is used to manipulate the variables that
214 may be sent through the TELNET ENVIRON option. The initial
215 set of variables is taken from the users environment, with
216 only the DISPLAY and PRINTER variables being exported by
217 default. The USER variable is also exported if the -a or -l
218 options are used.
219 Valid arguments for the environ command are:
220 define variable value
222 Define the variable variable to have a value of
223 value. Any variables defined by this command are
224 automatically exported. The value may be enclosed
225 in single or double quotes so that tabs and spaces
226 may be included.
227 undefine variable
229 Remove variable from the list of environment vari‐
230 ables.
231 export variable
233 Mark the variable variable to be exported to the
234 remote side.
235 unexport variable
237 Mark the variable variable to not be exported
238 unless explicitly asked for by the remote side.
239 list List the current set of environment variables.
241 Those marked with a * will be sent automatically,
242 other variables will only be sent if explicitly
243 requested.
244 ? Prints out help information for the environ com‐
246 mand.
247 logout Sends the TELNET LOGOUT option to the remote side. This com‐
249 mand is similar to a close command; however, if the remote
250 side does not support the LOGOUT option, nothing happens. If,
251 however, the remote side does support the LOGOUT option, this
252 command should cause the remote side to close the TELNET con‐
253 nection. If the remote side also supports the concept of sus‐
254 pending a user's session for later reattachment, the logout
255 argument indicates that you should terminate the session imme‐
256 diately.
257 mode type type is one of several options, depending on the state of the
259 TELNET session. The remote host is asked for permission to go
260 into the requested mode. If the remote host is capable of
261 entering that mode, the requested mode will be entered.
262 character Disable the TELNET LINEMODE option, or, if the
264 remote side does not understand the LINEMODE
265 option, then enter ``character at a time'' mode.
266 line Enable the TELNET LINEMODE option, or, if the
268 remote side does not understand the LINEMODE
269 option, then attempt to enter ``old-line-by-
270 line'' mode.
271 isig (-isig) Attempt to enable (disable) the TRAPSIG mode of
273 the LINEMODE option. This requires that the
274 LINEMODE option be enabled.
275 edit (-edit) Attempt to enable (disable) the EDIT mode of the
277 LINEMODE option. This requires that the
278 LINEMODE option be enabled.
279 softtabs (-softtabs)
281 Attempt to enable (disable) the SOFT_TAB mode of
282 the LINEMODE option. This requires that the
283 LINEMODE option be enabled.
284 litecho (-litecho)
286 Attempt to enable (disable) the LIT_ECHO mode of
287 the LINEMODE option. This requires that the
288 LINEMODE option be enabled.
289 ? Prints out help information for the mode com‐
291 mand.
292 open host [-l user] [[-] port]
294 Open a connection to the named host. If no port number is
295 specified, telnet will attempt to contact a TELNET server at
296 the default port. The host specification may be either a host
297 name (see hosts(5)) or an Internet address specified in the
298 ``dot notation'' (see inet(3)). The -l option may be used to
299 specify the user name to be passed to the remote system via
300 the ENVIRON option. When connecting to a non-standard port,
301 telnet omits any automatic initiation of TELNET options. When
302 the port number is preceded by a minus sign, the initial
303 option negotiation is done. After establishing a connection,
304 the file .telnetrc in the user's home directory is opened.
305 Lines beginning with a ``#'' are comment lines. Blank lines
306 are ignored. Lines that begin without whitespace are the
307 start of a machine entry. The first thing on the line is the
308 name of the machine that is being connected to. The rest of
309 the line, and successive lines that begin with whitespace are
310 assumed to be telnet commands and are processed as if they had
311 been typed in manually to the telnet command prompt.
312 quit Close any open TELNET session and exit telnet. An end-of-file
314 (in command mode) will also close a session and exit.
315 send arguments
317 Sends one or more special character sequences to the remote
318 host. The following are the arguments which may be specified
319 (more than one argument may be specified at a time):
320 abort Sends the TELNET ABORT (Abort processes) sequence.
322 ao Sends the TELNET AO (Abort Output) sequence, which
324 should cause the remote system to flush all output
325 from the remote system to the user's terminal.
326 ayt Sends the TELNET AYT (Are You There) sequence, to
328 which the remote system may or may not choose to
329 respond.
330 brk Sends the TELNET BRK (Break) sequence, which may have
332 significance to the remote system.
333 ec Sends the TELNET EC (Erase Character) sequence, which
335 should cause the remote system to erase the last char‐
336 acter entered.
337 el Sends the TELNET EL (Erase Line) sequence, which
339 should cause the remote system to erase the line cur‐
340 rently being entered.
341 eof Sends the TELNET EOF (End Of File) sequence.
343 eor Sends the TELNET EOR (End of Record) sequence.
345 escape Sends the current telnet escape character (initially
347 ``^]'').
348 ga Sends the TELNET GA (Go Ahead) sequence, which likely
350 has no significance to the remote system.
351 getstatus
353 If the remote side supports the TELNET STATUS command,
354 getstatus will send the subnegotiation to request that
355 the server send its current option status.
356 ip Sends the TELNET IP (Interrupt Process) sequence,
358 which should cause the remote system to abort the cur‐
359 rently running process.
360 nop Sends the TELNET NOP (No OPeration) sequence.
362 susp Sends the TELNET SUSP (SUSPend process) sequence.
364 synch Sends the TELNET SYNCH sequence. This sequence causes
366 the remote system to discard all previously typed (but
367 not yet read) input. This sequence is sent as TCP
368 urgent data (and may not work if the remote system is
369 a 4.2BSD system -- if it doesn't work, a lower case
370 ``r'' may be echoed on the terminal).
371 do cmd Sends the TELNET DO cmd sequence. cmd can be either a
373 decimal number between 0 and 255, or a symbolic name
374 for a specific TELNET command. cmd can also be either
375 help or ? to print out help information, including a
376 list of known symbolic names.
377 dont cmd
379 Sends the TELNET DONT cmd sequence. cmd can be either
380 a decimal number between 0 and 255, or a symbolic name
381 for a specific TELNET command. cmd can also be either
382 help or ? to print out help information, including a
383 list of known symbolic names.
384 will cmd
386 Sends the TELNET WILL cmd sequence. cmd can be either
387 a decimal number between 0 and 255, or a symbolic name
388 for a specific TELNET command. cmd can also be either
389 help or ? to print out help information, including a
390 list of known symbolic names.
391 wont cmd
393 Sends the TELNET WONT cmd sequence. cmd can be either
394 a decimal number between 0 and 255, or a symbolic name
395 for a specific TELNET command. cmd can also be either
396 help or ? to print out help information, including a
397 list of known symbolic names.
398 ? Prints out help information for the send command.
400 set argument value
402 unset argument value
404 The set command will set any one of a number of telnet vari‐
405 ables to a specific value or to TRUE. The special value off
406 turns off the function associated with the variable; this is
407 equivalent to using the unset command. The unset command will
408 disable or set to FALSE any of the specified functions. The
409 values of variables may be interrogated with the display com‐
410 mand. The variables which may be set or unset, but not tog‐
411 gled, are listed here. In addition, any of the variables for
412 the toggle command may be explicitly set or unset using the
413 set and unset commands.
414 ayt If TELNET is in localchars mode, or LINEMODE is
416 enabled, and the status character is typed, a TELNET
417 AYT sequence (see send ayt preceding) is sent to the
418 remote host. The initial value for the "Are You
419 There" character is the terminal's status character.
420 echo This is the value (initially ``^E'') which, when in
422 ``line by line'' mode, toggles between doing local
423 echoing of entered characters (for normal processing),
424 and suppressing echoing of entered characters (for
425 entering, say, a password).
426 eof If telnet is operating in LINEMODE or ``old line by
428 line'' mode, entering this character as the first
429 character on a line will cause this character to be
430 sent to the remote system. The initial value of the
431 eof character is taken to be the terminal's eof char‐
432 acter.
433 erase If telnet is in localchars mode (see toggle localchars
435 below), and if telnet is operating in ``character at a
436 time'' mode, then when this character is typed, a
437 TELNET EC sequence (see send ec above) is sent to the
438 remote system. The initial value for the erase char‐
439 acter is taken to be the terminal's erase character.
440 escape This is the telnet escape character (initially ``^['')
442 which causes entry into telnet command mode (when con‐
443 nected to a remote system).
444 flushoutput
446 If telnet is in localchars mode (see toggle localchars
447 below) and the flushoutput character is typed, a
448 TELNET AO sequence (see send ao above) is sent to the
449 remote host. The initial value for the flush charac‐
450 ter is taken to be the terminal's flush character.
451 forw1
453 forw2 If TELNET is operating in LINEMODE, these are the
455 characters that, when typed, cause partial lines to be
456 forwarded to the remote system. The initial value for
457 the forwarding characters are taken from the termi‐
458 nal's eol and eol2 characters.
459 interrupt
461 If telnet is in localchars mode (see toggle localchars
462 below) and the interrupt character is typed, a TELNET
463 IP sequence (see send ip above) is sent to the remote
464 host. The initial value for the interrupt character
465 is taken to be the terminal's intr character.
466 kill If telnet is in localchars mode (see toggle localchars
468 below), and if telnet is operating in ``character at a
469 time'' mode, then when this character is typed, a
470 TELNET EL sequence (see send el above) is sent to the
471 remote system. The initial value for the kill charac‐
472 ter is taken to be the terminal's kill character.
473 lnext If telnet is operating in LINEMODE or ``old line by
475 line'' mode, then this character is taken to be the
476 terminal's lnext character. The initial value for the
477 lnext character is taken to be the terminal's lnext
478 character.
479 quit If telnet is in localchars mode (see toggle localchars
481 below) and the quit character is typed, a TELNET BRK
482 sequence (see send brk above) is sent to the remote
483 host. The initial value for the quit character is
484 taken to be the terminal's quit character.
485 reprint
487 If telnet is operating in LINEMODE or old line by
488 line'' mode, then this character is taken to be the
489 terminal's reprint character. The initial value for
490 the reprint character is taken to be the terminal's
491 reprint character.
492 rlogin This is the rlogin escape character. If set, the nor‐
494 mal TELNET escape character is ignored unless it is
495 preceded by this character at the beginning of a line.
496 This character, at the beginning of a line, followed
497 by a "." closes the connection; when followed by a ^Z
498 it suspends the telnet command. The initial state is
499 to disable the rlogin escape character.
500 start If the TELNET TOGGLE-FLOW-CONTROL option has been
502 enabled, then this character is taken to be the termi‐
503 nal's start character. The initial value for the
504 start character is taken to be the terminal's start
505 character.
506 stop If the TELNET TOGGLE-FLOW-CONTROL option has been
508 enabled, then this character is taken to be the termi‐
509 nal's stop character. The initial value for the stop
510 character is taken to be the terminal's stop charac‐
511 ter.
512 susp If telnet is in localchars mode, or LINEMODE is
514 enabled, and the suspend character is typed, a TELNET
515 SUSP sequence (see send susp above) is sent to the
516 remote host. The initial value for the suspend char‐
517 acter is taken to be the terminal's suspend character.
518 tracefile
520 This is the file to which the output, caused by
521 netdata or option tracing being TRUE, will be written.
522 If it is set to “-”, then tracing information will be
523 written to standard output (the default).
524 worderase
526 If telnet is operating in LINEMODE or ``old line by
527 line'' mode, then this character is taken to be the
528 terminal's worderase character. The initial value for
529 the worderase character is taken to be the terminal's
530 worderase character.
531 ? Displays the legal set (unset) commands.
533 skey sequence challenge
535 The skey command computes a response to the S/Key challenge.
536 See skey(1) for more information on the S/Key system.
537 slc state The slc command (Set Local Characters) is used to set or
539 change the state of the special characters when the TELNET
540 LINEMODE option has been enabled. Special characters are
541 characters that get mapped to TELNET commands sequences (like
542 ip or quit) or line editing characters (like erase and kill).
543 By default, the local special characters are exported.
544 check Verify the current settings for the current spe‐
546 cial characters. The remote side is requested to
547 send all the current special character settings,
548 and if there are any discrepancies with the local
549 side, the local side will switch to the remote
550 value.
551 export Switch to the local defaults for the special char‐
553 acters. The local default characters are those of
554 the local terminal at the time when telnet was
555 started.
556 import Switch to the remote defaults for the special
558 characters. The remote default characters are
559 those of the remote system at the time when the
560 TELNET connection was established.
561 ? Prints out help information for the slc command.
563 status Show the current status of telnet. This includes the peer one
565 is connected to, as well as the current mode.
566 toggle arguments [...]
568 Toggle (between TRUE and FALSE) various flags that control how
569 telnet responds to events. These flags may be set explicitly
570 to TRUE or FALSE using the set and unset commands listed
571 above. More than one argument may be specified. The state of
572 these flags may be interrogated with the display command.
573 Valid arguments are:
574 authdebug Turns on debugging information for the authenti‐
576 cation code.
577 autoflush If autoflush and localchars are both TRUE, then
579 when the ao or quit characters are recognized
580 (and transformed into TELNET sequences; see set
581 above for details), telnet refuses to display
582 any data on the user's terminal until the remote
583 system acknowledges (via a TELNET TIMING MARK
584 option) that it has processed those TELNET
585 sequences. The initial value for this toggle is
586 TRUE if the terminal user had not done an "stty
587 noflsh", otherwise FALSE (see stty(1)).
588 autodecrypt When the TELNET ENCRYPT option is negotiated, by
590 default the actual encryption (decryption) of
591 the data stream does not start automatically.
592 The autoencrypt (autodecrypt) command states
593 that encryption of the output (input) stream
594 should be enabled as soon as possible.
595 autologin If the remote side supports the TELNET
597 AUTHENTICATION option TELNET attempts to use it
598 to perform automatic authentication. If the
599 AUTHENTICATION option is not supported, the
600 user's login name are propagated through the
601 TELNET ENVIRON option. This command is the same
602 as specifying a option on the open command.
603 autosynch If autosynch and localchars are both TRUE, then
605 when either the intr or quit character is typed
606 (see set above for descriptions of the intr and
607 quit characters), the resulting TELNET sequence
608 sent is followed by the TELNET SYNCH sequence.
609 This procedure should cause the remote system to
610 begin throwing away all previously typed input
611 until both of the TELNET sequences have been
612 read and acted upon. The initial value of this
613 toggle is FALSE.
614 binary Enable or disable the TELNET BINARY option on
616 both input and output.
617 inbinary Enable or disable the TELNET BINARY option on
619 input.
620 outbinary Enable or disable the TELNET BINARY option on
622 output.
623 crlf If this is TRUE, then carriage returns will be
625 sent as <CR><LF>. If this is FALSE, then car‐
626 riage returns will be send as <CR><NUL>. The
627 initial value for this toggle is FALSE.
628 crmod Toggle carriage return mode. When this mode is
630 enabled, most carriage return characters
631 received from the remote host will be mapped
632 into a carriage return followed by a line feed.
633 This mode does not affect those characters typed
634 by the user, only those received from the remote
635 host. This mode is not very useful unless the
636 remote host only sends carriage return, but
637 never line feeds. The initial value for this
638 toggle is FALSE.
639 debug Toggles socket level debugging (useful only to
641 the superuser). The initial value for this tog‐
642 gle is FALSE.
643 encdebug Turns on debugging information for the encryp‐
645 tion code.
646 localchars If this is TRUE, then the flush, interrupt,
648 quit, erase, and kill characters (see set above)
649 are recognized locally, and transformed into
650 (hopefully) appropriate TELNET control sequences
651 (respectively ao, ip, brk, ec, and el; see send
652 above). The initial value for this toggle is
653 TRUE in ``old line by line'' mode, and FALSE in
654 ``character at a time'' mode. When the LINEMODE
655 option is enabled, the value of localchars is
656 ignored, and assumed to always be TRUE. If
657 LINEMODE has ever been enabled, then quit is
658 sent as abort, and eof and suspend are sent as
659 eof and susp (see send above).
660 netdata Toggles the display of all network data (in
662 hexadecimal format). The initial value for this
663 toggle is FALSE.
664 options Toggles the display of some internal telnet pro‐
666 tocol processing (having to do with TELNET
667 options). The initial value for this toggle is
668 FALSE.
669 prettydump When the netdata toggle is enabled, if
671 prettydump is enabled the output from the
672 netdata command will be formatted in a more user
673 readable format. Spaces are put between each
674 character in the output, and the beginning of
675 any TELNET escape sequence is preceded by a '*'
676 to aid in locating them.
677 skiprc When the skiprc toggle is TRUE, TELNET skips the
679 reading of the .telnetrc file in the user's home
680 directory when connections are opened. The ini‐
681 tial value for this toggle is FALSE.
682 termdata Toggles the display of all terminal data (in
684 hexadecimal format). The initial value for this
685 toggle is FALSE.
686 verbose_encrypt
688 When the verbose_encrypt toggle is TRUE, telnet
689 prints out a message each time encryption is
690 enabled or disabled. The initial value for this
691 toggle is FALSE.
692 ? Displays the legal toggle commands.
694 z Suspend telnet. This command only works when the user is
696 using the csh(1).
697 ! [command]
699 Execute a single command in a subshell on the local system.
700 If command is omitted, then an interactive subshell is
701 invoked.
702 ? [command]
704 Get help. With no arguments, telnet prints a help summary.
705 If a command is specified, telnet will print the help informa‐
706 tion for just that command.
707
709 telnet uses at least the HOME, SHELL, DISPLAY, and TERM environment vari‐
710 ables. Other environment variables may be propagated to the other side
711 via the TELNET ENVIRON option.
712
714 ~/.telnetrc user customized telnet startup values
715
717 The telnet command appeared in 4.2BSD.
718
720 On some remote systems, echo has to be turned off manually when in ``old
721 line by line'' mode.
722 In ``old line by line'' mode or LINEMODE the terminal's eof character is
724 only recognized (and sent to the remote system) when it is the first
725 character on a line.
726 Source routing is not supported yet for IPv6.
728BSD February 3, 1994 BSD