1TELNET(1C) TELNET(1C)
2
6 telnet - user interface to the TELNET protocol
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9 telnet [ host [ port ] ]
10
12 Telnet is used to communicate with another host using the TELNET proto‐
13 col. If telnet is invoked without arguments, it enters command mode,
14 indicated by its prompt (“telnet>”). In this mode, it accepts and exe‐
15 cutes the commands listed below. If it is invoked with arguments, it
16 performs an open command (see below) with those arguments.
17 Once a connection has been opened, telnet enters an input mode. The
19 input mode entered will be either “character at a time” or “line by
20 line” depending on what the remote system supports.
21 In “character at a time” mode, most text typed is immediately sent to
23 the remote host for processing.
24 In “line by line” mode, all text is echoed locally, and (normally) only
26 completed lines are sent to the remote host. The “local echo charac‐
27 ter” (initially “^E”) may be used to turn off and on the local echo
28 (this would mostly be used to enter passwords without the password
29 being echoed).
30 In either mode, if the localchars toggle is TRUE (the default in line
32 mode; see below), the user's quit, intr, and flush characters are
33 trapped locally, and sent as TELNET protocol sequences to the remote
34 side. There are options (see toggle autoflush and toggle autosynch
35 below) which cause this action to flush subsequent output to the termi‐
36 nal (until the remote host acknowledges the TELNET sequence) and flush
37 previous terminal input (in the case of quit and intr).
38 While connected to a remote host, telnet command mode may be entered by
40 typing the telnet “escape character” (initially “^]”). When in command
41 mode, the normal terminal editing conventions are available.
42 COMMANDS
44 The following commands are available. Only enough of each command to
46 uniquely identify it need be typed (this is also true for arguments to
47 the mode, set, toggle, and display commands).
48 open host [ port ]
50 Open a connection to the named host. If no port number is spec‐
51 ified, telnet will attempt to contact a TELNET server at the
52 default port. The host specification may be either a host name
53 (see hosts(5)) or an Internet address specified in the “dot
54 notation” (see inet(3N)).
55 close
57 Close a TELNET session and return to command mode.
58 quit
60 Close any open TELNET session and exit telnet. An end of file
61 (in command mode) will also close a session and exit.
62 z
64 Suspend telnet. This command only works when the user is using
65 the csh(1).
66 mode type
68 Type is either line (for “line by line” mode) or character (for
69 “character at a time” mode). The remote host is asked for per‐
70 mission to go into the requested mode. If the remote host is
71 capable of entering that mode, the requested mode will be
72 entered.
73 status
75 Show the current status of telnet. This includes the peer one
76 is connected to, as well as the current mode.
77 display [ argument... ]
79 Displays all, or some, of the set and toggle values (see below).
80 ? [ command ]
82 Get help. With no arguments, telnet prints a help summary. If
83 a command is specified, telnet will print the help information
84 for just that command.
85 send arguments
87 Sends one or more special character sequences to the remote
88 host. The following are the arguments which may be specified
89 (more than one argument may be specified at a time):
90 escape
92 Sends the current telnet escape character (initially
93 “^]”).
94 synch
96 Sends the TELNET SYNCH sequence. This sequence causes
97 the remote system to discard all previously typed (but
98 not yet read) input. This sequence is sent as TCP urgent
99 data (and may not work if the remote system is a 4.2 BSD
100 system -- if it doesn't work, a lower case “r” may be
101 echoed on the terminal).
102 brk
104 Sends the TELNET BRK (Break) sequence, which may have
105 significance to the remote system.
106 ip
108 Sends the TELNET IP (Interrupt Process) sequence, which
109 should cause the remote system to abort the currently
110 running process.
111 ao
113 Sends the TELNET AO (Abort Output) sequence, which should
114 cause the remote system to flush all output from the
115 remote system to the user's terminal.
116 ayt
118 Sends the TELNET AYT (Are You There) sequence, to which
119 the remote system may or may not choose to respond.
120 ec
122 Sends the TELNET EC (Erase Character) sequence, which
123 should cause the remote system to erase the last charac‐
124 ter entered.
125 el
127 Sends the TELNET EL (Erase Line) sequence, which should
128 cause the remote system to erase the line currently being
129 entered.
130 ga
132 Sends the TELNET GA (Go Ahead) sequence, which likely has
133 no significance to the remote system.
134 nop
136 Sends the TELNET NOP (No OPeration) sequence.
137 ?
139 Prints out help information for the send command.
140 set argument value
142 Set any one of a number of telnet variables to a specific value.
143 The special value “off” turns off the function associated with
144 the variable. The values of variables may be interrogated with
145 the display command. The variables which may be specified are:
146 echo
148 This is the value (initially “^E”) which, when in “line
149 by line” mode, toggles between doing local echoing of
150 entered characters (for normal processing), and suppress‐
151 ing echoing of entered characters (for entering, say, a
152 password).
153 escape
155 This is the telnet escape character (initially “^[”)
156 which causes entry into telnet command mode (when con‐
157 nected to a remote system).
158 interrupt
160 If telnet is in localchars mode (see toggle localchars
161 below) and the interrupt character is typed, a TELNET IP
162 sequence (see send ip above) is sent to the remote host.
163 The initial value for the interrupt character is taken to
164 be the terminal's intr character.
165 quit
167 If telnet is in localchars mode (see toggle localchars
168 below) and the quit character is typed, a TELNET BRK
169 sequence (see send brk above) is sent to the remote host.
170 The initial value for the quit character is taken to be
171 the terminal's quit character.
172 flushoutput
174 If telnet is in localchars mode (see toggle localchars
175 below) and the flushoutput character is typed, a TELNET
176 AO sequence (see send ao above) is sent to the remote
177 host. The initial value for the flush character is taken
178 to be the terminal's flush character.
179 erase
181 If telnet is in localchars mode (see toggle localchars
182 below), and if telnet is operating in “character at a
183 time” mode, then when this character is typed, a TELNET
184 EC sequence (see send ec above) is sent to the remote
185 system. The initial value for the erase character is
186 taken to be the terminal's erase character.
187 kill
189 If telnet is in localchars mode (see toggle localchars
190 below), and if telnet is operating in “character at a
191 time” mode, then when this character is typed, a TELNET
192 EL sequence (see send el above) is sent to the remote
193 system. The initial value for the kill character is
194 taken to be the terminal's kill character.
195 eof
197 If telnet is operating in “line by line” mode, entering
198 this character as the first character on a line will
199 cause this character to be sent to the remote system.
200 The initial value of the eof character is taken to be the
201 terminal's eof character.
202 toggle arguments...
204 Toggle (between TRUE and FALSE) various flags that control how
205 telnet responds to events. More than one argument may be speci‐
206 fied. The state of these flags may be interrogated with the
207 display command. Valid arguments are:
208 localchars
210 If this is TRUE, then the flush, interrupt, quit, erase,
211 and kill characters (see set above) are recognized
212 locally, and transformed into (hopefully) appropriate
213 TELNET control sequences (respectively ao, ip, brk, ec,
214 and el; see send above). The initial value for this tog‐
215 gle is TRUE in “line by line” mode, and FALSE in “charac‐
216 ter at a time” mode.
217 autoflush
219 If autoflush and localchars are both TRUE, then when the
220 ao, intr, or quit characters are recognized (and trans‐
221 formed into TELNET sequences; see set above for details),
222 telnet refuses to display any data on the user's terminal
223 until the remote system acknowledges (via a TELNET Timing
224 Mark option) that it has processed those TELNET
225 sequences. The initial value for this toggle is TRUE if
226 the terminal user had not done an "stty noflsh", other‐
227 wise FALSE (see stty(1)).
228 autosynch
230 If autosynch and localchars are both TRUE, then when
231 either the intr or quit characters is typed (see set
232 above for descriptions of the intr and quit characters),
233 the resulting TELNET sequence sent is followed by the
234 TELNET SYNCH sequence. This procedure should cause the
235 remote system to begin throwing away all previously typed
236 input until both of the TELNET sequences have been read
237 and acted upon. The initial value of this toggle is
238 FALSE.
239 crmod
241 Toggle carriage return mode. When this mode is enabled,
242 most carriage return characters received from the remote
243 host will be mapped into a carriage return followed by a
244 line feed. This mode does not affect those characters
245 typed by the user, only those received from the remote
246 host. This mode is not very useful unless the remote
247 host only sends carriage return, but never line feed.
248 The initial value for this toggle is FALSE.
249 debug
251 Toggles socket level debugging (useful only to the supe‐
252 ruser). The initial value for this toggle is FALSE.
253 options
255 Toggles the display of some internal telnet protocol pro‐
256 cessing (having to do with TELNET options). The initial
257 value for this toggle is FALSE.
258 netdata
260 Toggles the display of all network data (in hexadecimal
261 format). The initial value for this toggle is FALSE.
262 ?
264 Displays the legal toggle commands.
265
267 There is no adequate way for dealing with flow control.
268 On some remote systems, echo has to be turned off manually when in
270 “line by line” mode.
271 There is enough settable state to justify a .telnetrc file.
273 No capability for a .telnetrc file is provided.
275 In “line by line” mode, the terminal's eof character is only recognized
277 (and sent to the remote system) when it is the first character on a
278 line.
2794.2 Berkeley Distribution May 10, 1986 TELNET(1C)