User Commands telnet(1)
NAME
telnet - user interface to a remote system using the TELNET
protocol
SYNOPSIS
telnet [-8EFKLacdfrx] [-X atype] [-e escapechar]
[-k realm] [-l user] [-n file]
[ [ [!] @hop1 [@hop2...] @] host [port]
DESCRIPTION
The telnet utility communicates with another host using the
TELNET protocol. If telnet is invoked without arguments, it
enters command mode, indicated by its prompt, telnet>. In
this mode, it accepts and executes its associated commands.
See USAGE. If it is invoked with arguments, it performs an
open command with those arguments.
If, for example, a host is specified as @hop1@hop2@host, the
connection goes through hosts hop1 and hop2, using loose
source routing to end at host. If a leading ! is used, the
connection follows strict source routing. Notice that when
telnet uses IPv6, it can only use loose source routing, and
the connection ignores the !.
Once a connection has been opened, telnet enters input mode.
In this mode, text typed is sent to the remote host. The
input mode entered will be either "line mode", "character at
a time", or "old line by line", depending upon what the
remote system supports.
In "line mode", character processing is done on the local
system, under the control of the remote system. When input
editing or character echoing is to be disabled, the remote
system will relay that information. The remote system will
also relay changes to any special characters that happen on
the remote system, so that they can take effect on the local
system.
In "character at a time" mode, most text typed is immedi-
ately sent to the remote host for processing.
In "old line by line" mode, all text is echoed locally, and
(normally) only completed lines are sent to the remote host.
The "local echo character" (initially ^E) may be used to
turn off and on the local echo. (Use this mostly to enter
passwords without the password being echoed.).
SunOS 5.11 Last change: 17 Aug 2006 1
User Commands telnet(1)
If the "line mode" option is enabled, or if the localchars
toggle is TRUE (the default in "old line by line" mode), the
user's quit, intr, and flush characters are trapped locally,
and sent as TELNET protocol sequences to the remote side. If
"line mode" has ever been enabled, then the user's susp and
eof are also sent as TELNET protocol sequences. quit is then
sent as a TELNET ABORT instead of BREAK. The options toggle
autoflush and toggle autosynch cause this action to flush
subsequent output to the terminal (until the remote host
acknowledges the TELNET sequence); and to flush previous
terminal input, in the case of quit and intr.
While connected to a remote host, the user can enter telnet
command mode by typing the telnet escape character (ini-
tially ^]). When in command mode, the normal terminal edit-
ing conventions are available. Pressing RETURN at the telnet
command prompt causes telnet to exit command mode.
OPTIONS
The following options are supported:
-8
Specifies an 8-bit data path. Negotiating the TELNET
BINARY option is attempted for both input and output.
-a
Attempts automatic login. This sends the user name by
means of the USER variable of the ENVIRON option, if
supported by the remote system. The name used is that of
the current user as returned by getlogin(3C) if it
agrees with the current user ID. Otherwise, it is the
name associated with the user ID.
-c
Disables the reading of the user's telnetrc file. (See
the toggle skiprc command on this reference page.)
-d
Sets the initial value of the debug toggle to TRUE.
-e escapechar
Sets the initial escape character to escapechar.
SunOS 5.11 Last change: 17 Aug 2006 2
User Commands telnet(1)
escapechar may also be a two character sequence con-
sisting of ^ (Control key) followed by one character. If
the second character is ?, the DEL character is
selected. Otherwise, the second character is converted
to a control character and used as the escape character.
If escapechar is defined as the null string (that is,
-e ''), this is equivalent to -e '^@' (Control-@). To
specify that no character can be the escape character,
use the -E option.
-E
Stops any character from being recognized as an escape
character.
-f
Forwards a copy of the local credentials to the remote
system.
-F
Forwards a forwardable copy of the local credentials to
the remote system.
-k realm
If Kerberos authentication is being used, requests that
telnet obtain tickets for the remote host in realm
instead of the remote host's default realm as determined
inkrb5.conf(4).
-K
Specifies no automatic login to the remote system.
-l user
When connecting to a remote system that understands the
ENVIRON option, then user will be sent to the remote
system as the value for the ENVIRON variable USER.
-L
Specifies an 8-bit data path on output. This causes the
SunOS 5.11 Last change: 17 Aug 2006 3
User Commands telnet(1)
BINARY option to be negotiated on output.
-n tracefile
Opens tracefile for recording trace information. See the
set tracefile command below.
-r
Specifies a user interface similar to rlogin. In this
mode, the escape character is set to the tilde (~) char-
acter, unless modified by the -e option. The rlogin
escape character is only recognized when it is preceded
by a carriage return. In this mode, the telnet escape
character, normally '^]', must still precede a telnet
command. The rlogin escape character can also be fol-
lowed by '.\r' or '^Z', and, like rlogin(1), closes or
suspends the connection, respectively. This option is an
uncommitted interface and may change in the future.
-x
Turns on encryption of the data stream. When this option
is turned on, telnet will exit with an error if authen-
tication cannot be negotiated or if encryption cannot be
turned on.
-X atype
Disables the atype type of authentication.
USAGE
telnet Commands
The commands described in this section are available with
telnet. It is necessary to type only enough of each command
to uniquely identify it. (This is also true for arguments to
the mode, set, toggle, unset, environ, and display com-
mands.)
auth argument ...
The auth command manipulates the information sent
through the TELNET AUTHENTICATE option. Valid arguments
for the auth command are as follows:
disable type
SunOS 5.11 Last change: 17 Aug 2006 4
User Commands telnet(1)
Disables the specified type of authentication. To
obtain a list of available types, use the auth dis-
able ? command.
enable type
Enables the specified type of authentication. To
obtain a list of available types, use the auth
enable ? command.
status
Lists the current status of the various types of
authentication.
open [-l user ] [ [!] @hop1 [@hop2 ...]@host [ port ]
Open a connection to the named host. If no port number
is specified, telnet will attempt to contact a TELNET
server at the default port. The host specification may
be either a host name (see hosts(4)) or an Internet
address specified in the "dot notation" (see inet(7P) or
inet6(7P)). If the host is specified as @hop1@hop2@host,
the connection goes through hosts hop1 and hop2, using
loose source routing to end at host. The @ symbol is
required as a separator between the hosts specified. If
a leading ! is used with IPv4, the connection follows
strict source routing.
The -l option passes the user as the value of the
ENVIRON variable USER to the remote system.
close
Close any open TELNET session and exit telnet. An EOF
(in command mode) will also close a session and exit.
encrypt
The encrypt command manipulates the information sent
through the TELNET ENCRYPT option.
Valid arguments for the encrypt command are as follows:
disable type [inputoutput]
SunOS 5.11 Last change: 17 Aug 2006 5
User Commands telnet(1)
Disables the specified type of encryption. If you
omit the input and output, both input and output are
disabled. To obtain a list of available types, use
the encrypt disable ? command.
enable type [inputoutput]
Enables the specified type of encryption. If you
omit input and output, both input and output are
enabled. To obtain a list of available types, use
the encrypt enable ? command.
input
This is the same as the encrypt start input command.
-input
This is the same as the encrypt stop input command.
output
This is the same as the encrypt start output com-
mand.
-output
This is the same as the encrypt stop output command.
start [inputoutput]
Attempts to start encryption. If you omit input and
output, both input and output are enabled. To obtain
a list of available types, use the encrypt enable ?
command.
status
Lists the current status of encryption.
stop [inputoutput]
Stops encryption. If you omit input and output,
encryption is on both input and output.
SunOS 5.11 Last change: 17 Aug 2006 6
User Commands telnet(1)
type type
Sets the default type of encryption to be used with
later encrypt start or encrypt stop commands.
quit
Same as close.
z
Suspend telnet. This command only works when the user is
using a shell that supports job control, such as sh(1).
mode type
The remote host is asked for permission to go into the
requested mode. If the remote host is capable of enter-
ing that mode, the requested mode will be entered. The
argument type is one of the following:
character
Disable the TELNET LINEMODE option, or, if the
remote side does not understand the LINEMODE option,
then enter "character at a time" mode.
line
Enable the TELNET LINEMODE option, or, if the remote
side does not understand the LINEMODE option, then
attempt to enter "old-line-by-line" mode.
isig (-isig)
Attempt to enable (disable) the TRAPSIG mode of the
LINEMODE option. This requires that the LINEMODE
option be enabled.
edit (-edit)
Attempt to enable (disable) the EDIT mode of the
LINEMODE option. This requires that the LINEMODE
option be enabled.
SunOS 5.11 Last change: 17 Aug 2006 7
User Commands telnet(1)
softtabs (-softtabs)
Attempt to enable (disable) the SOFTAB mode of the
LINEMODE option. This requires that the LINEMODE
option be enabled.
litecho (-litecho)
Attempt to enable (disable) the LITECHO mode of the
LINEMODE option. This requires that the LINEMODE
option be enabled.
?
Prints out help information for the mode command.
status
Show the current status of telnet. This includes the
peer one is connected to, as well as the current mode.
display
[argument...] Display all, or some, of the set and tog-
gle values (see toggle argument...).
?
[command] Get help. With no arguments, telnet prints a
help summary. If a command is specified, telnet will
print the help information for just that command.
send argument...
Send one or more special character sequences to the
remote host. The following are the arguments that can be
specified (more than one argument may be specified at a
time):
escape
Send the current telnet escape character (initially
^]).
SunOS 5.11 Last change: 17 Aug 2006 8
User Commands telnet(1)
synch
Send the TELNET SYNCH sequence. This sequence dis-
cards all previously typed, but not yet read, input
on the remote system. This sequence is sent as TCP
urgent data and may not work if the remote system is
a 4.2 BSD system. If it does not work, a lowercase
"r" may be echoed on the terminal.
brk or break
Send the TELNET BRK (Break) sequence, which may have
significance to the remote system.
ip
Send the TELNET IP (Interrupt Process) sequence,
which aborts the currently running process on the
remote system.
abort
Send the TELNET ABORT (Abort Process) sequence.
ao
Send the TELNET AO (Abort Output) sequence, which
flushes all output from the remote system to the
user's terminal.
ayt
Send the TELNET AYT (Are You There) sequence, to
which the remote system may or may not respond.
ec
Send the TELNET EC (Erase Character) sequence, which
erases the last character entered.
el
Send the TELNET EL (Erase Line) sequence, which
should cause the remote system to erase the line
currently being entered.
SunOS 5.11 Last change: 17 Aug 2006 9
User Commands telnet(1)
eof
Send the TELNET EOF (End Of File) sequence.
eor
Send the TELNET EOR (End Of Record) sequence.
ga
Send the TELNET GA (Go Ahead) sequence, which prob-
ably has no significance for the remote system.
getstatus
If the remote side supports the TELNET STATUS com-
mand, getstatus will send the subnegotiation to
request that the server send its current option
status.
nop
Send the TELNET NOP (No Operation) sequence.
susp
Send the TELNET SUSP (Suspend Process) sequence.
do option
dont option
will option
wont option
Send the TELNET protocol option negotiation indi-
cated. Option may be the text name of the protocol
option, or the number corresponding to the option.
The command will be silently ignored if the option
negotiation indicated is not valid in the current
state. If the option is given as help or ?, the list
of option names known is listed. This command is
mostly useful for unusual debugging situations.
?
Print out help information for the send command.
SunOS 5.11 Last change: 17 Aug 2006 10
User Commands telnet(1)
set argument [value]
unset argument
Set any one of a number of telnet variables to a
specific value. The special value off turns off the
function associated with the variable. The values of
variables may be interrogated with the display command.
If value is omitted, the value is taken to be true, or
"on". If the unset form is used, the value is taken to
be false, or off. The variables that may be specified
are:
echo
This is the value (initially ^E) that, when in "line
by line" mode, toggles between local echoing of
entered characters for normal processing, and
suppressing echoing of entered characters, for exam-
ple, entering a password.
escape
This is the telnet escape character (initially ^])
that enters telnet command mode when connected to a
remote system.
interrupt
If telnet is in localchars mode (see toggle, local-
chars) and the interrupt character is typed, a TEL-
NET IP sequence (see send and ip) is sent to the
remote host. The initial value for the interrupt
character is taken to be the terminal's intr charac-
ter.
quit
If telnet is in localchars mode and the quit charac-
ter is typed, a TELNET BRK sequence (see send, brk)
is sent to the remote host. The initial value for
the quit character is taken to be the terminal's
quit character.
flushoutput
If telnet is in localchars mode and the flushoutput
character is typed, a TELNET AO sequence (see send,
ao) is sent to the remote host. The initial value
SunOS 5.11 Last change: 17 Aug 2006 11
User Commands telnet(1)
for the flush character is taken to be the
terminal's flush character.
erase
If telnet is in localchars mode and operating in
"character at a time" mode, then when the erase
character is typed, a TELNET EC sequence (see send,
ec) is sent to the remote system. The initial value
for the erase character is taken to be the
terminal's erase character.
kill
If telnet is in localchars mode and operating in
"character at a time" mode, then when the kill char-
acter is typed, a TELNET EL sequence (see send, el)
is sent to the remote system. The initial value for
the kill character is taken to be the terminal's
kill character.
eof
If telnet is operating in "line by line"/ mode,
entering the eof character as the first character on
a line sends this character to the remote system.
The initial value of eof is taken to be the
terminal's eof character.
ayt
If telnet is in localchars mode, or LINEMODE is
enabled, and the status character is typed, a TELNET
AYT ("Are You There") sequence is sent to the remote
host. (See send, ayt above.) The initial value for
ayt is the terminal's status character.
forw1
forw2
If telnet is operating in LINEMODE, and the forw1 or
forw2 characters are typed, this causes the forward-
ing of partial lines to the remote system. The ini-
tial values for the forwarding characters come from
the terminal's eol and eol2 characters.
SunOS 5.11 Last change: 17 Aug 2006 12
User Commands telnet(1)
lnext
If telnet is operating in LINEMODE or "old line by
line" mode, then the lnext character is assumed to
be the terminal's lnext character. The initial value
for the lnext character is taken to be the
terminal's lnext character.
reprint
If telnet is operating in LINEMODE or "old line by
line" mode, then the reprint character is assumed to
be the terminal's reprint character. The initial
value for reprint is taken to be the terminal's
reprint character.
rlogin
This is the rlogin escape character. If set, the
normal telnet escape character is ignored, unless it
is preceded by this character at the beginning of a
line. The rlogin character, at the beginning of a
line followed by a "." closes the connection. When
followed by a ^Z, the rlogin command suspends the
telnet command. The initial state is to disable the
rlogin escape character.
start
If the TELNET TOGLE-FLOW-CONTROL option has been
enabled, then the start character is taken to be the
terminal's start character. The initial value for
the kill character is taken to be the terminal's
start character.
stop
If the TELNET TOGLE-FLOW-CONTROL option has been
enabled, then the stop character is taken to be the
terminal's stop character. The initial value for the
kill character is taken to be the terminal's stop
character.
susp
If telnet is in localchars mode, or LINEMODE is
enabled, and the suspend character is typed, a
SunOS 5.11 Last change: 17 Aug 2006 13
User Commands telnet(1)
TELNET SUSP sequence (see send, susp above) is sent
to the remote host. The initial value for the
suspend character is taken to be the terminal's
suspend character.
tracefile
This is the file to which the output, generated when
the netdata or the debug option is TRUE, will be
written. If tracefile is set to "-", then tracing
information will be written to standard output (the
default).
worderase
If telnet is operating in LINEMODE or "old line by
line" mode, then this character is taken to be the
terminal's worderase character. The initial value
for the worderase character is taken to be the
terminal's worderase character.
?
Displays the legal set and unset commands.
slc state
The slc (Set Local Characters) command is used to set or
change the state of special characters when the TELNET
LINEMODE option has been enabled. Special characters are
characters that get mapped to TELNET commands sequences
(like ip or quit) or line editing characters (like erase
and kill). By default, the local special characters are
exported. The following values for state are valid:
check
Verifies the settings for the current special char-
acters. The remote side is requested to send all the
current special character settings. If there are any
discrepancies with the local side, the local set-
tings will switch to the remote values.
export
Switches to the local defaults for the special
SunOS 5.11 Last change: 17 Aug 2006 14
User Commands telnet(1)
characters. The local default characters are those
of the local terminal at the time when telnet was
started.
import
Switches to the remote defaults for the special
characters. The remote default characters are those
of the remote system at the time when the TELNET
connection was established.
?
Prints out help information for the slc command.
toggle argument...
Toggle between TRUE and FALSE the various flags that
control how telnet responds to events. More than one
argument may be specified. The state of these flags may
be interrogated with the display command. Valid argu-
ments are:
authdebug Turns on debugging information for
the authentication code.
autodecrypt When the TELNET ENCRYPT option is
negotiated, by default the actual
encryption (decryption) of the data
stream does not start automatically.
The autoencrypt (autodecrypt) com-
mand states that encryption of the
output (input) stream should be
enabled as soon as possible.
autologin If the remote side supports the TEL-
NET AUTHENTICATION option, telnet
attempts to use it to perform
automatic authentication. If the
AUTHENTICATION option is not sup-
ported, the user's login name is
propagated through the TELNET
ENVIRON option. This command is the
same as specifying the -a option on
the open command.
SunOS 5.11 Last change: 17 Aug 2006 15
User Commands telnet(1)
autoflush If autoflush and localchars are both
TRUE, then when the ao, intr, or
quit characters are recognized (and
transformed into TELNET sequences;
see set for details), telnet refuses
to display any data on the user's
terminal until the remote system
acknowledges (using a TELNET Timing
Mark option) that it has processed
those TELNET sequences. The initial
value for this toggle is TRUE if the
terminal user has not done an "stty
noflsh". Otherwise, the value is
FALSE (see stty(1)).
autosynch If autosynch and localchars are both
TRUE, then when either the interrupt
or quit characters are typed (see
set for descriptions of interrupt
and quit), the resulting TELNET
sequence sent is followed by the
TELNET SYNCH sequence. This pro-
cedure should cause the remote sys-
tem to begin throwing away all pre-
viously typed input until both of
the TELNET sequences have been read
and acted upon. The initial value of
this toggle is FALSE.
binary Enable or disable the TELNET BINARY
option on both input and output.
inbinary Enable or disable the TELNET BINARY
option on input.
outbinary Enable or disable the TELNET BINARY
option on output.
crlf Determines how carriage returns are
sent. If the value is TRUE, then
carriage returns will be sent as
. If the value is FALSE,
then carriage returns will be send
as . The initial value for
this toggle is FALSE.
SunOS 5.11 Last change: 17 Aug 2006 16
User Commands telnet(1)
crmod Toggle RETURN mode. When this mode
is enabled, most RETURN characters
received from the remote host will
be mapped into a RETURN followed by
a line feed. This mode does not
affect those characters typed by the
user, only those received from the
remote host. This mode is useful
only for remote hosts that send
RETURN but never send LINEFED. The
initial value for this toggle is
FALSE.
debug Toggle socket level debugging (only
available to the super-user). The
initial value for this toggle is
FALSE.
encdebug Turns on debugging information for
the encryption code.
localchars If this toggle is TRUE, then the
flush, interrupt, quit, erase, and
kill characters (see set) are recog-
nized locally, and transformed into
appropriate TELNET control
sequences, respectively ao, ip, brk,
ec, and el (see send). The initial
value for this toggle is TRUE in
"line by line" mode, and FALSE in
"character at a time" mode. When the
LINEMODE option is enabled, the
value of localchars is ignored, and
assumed always to be TRUE. If
LINEMODE has ever been enabled, then
quit is sent as abort, and eof and
suspend are sent as eof and susp
(see send above).
netdata Toggle the display of all network
data (in hexadecimal format). The
initial value for this toggle is
FALSE.
options Toggle the display of some internal
TELNET protocol processing (having
to do with telnet options). The
SunOS 5.11 Last change: 17 Aug 2006 17
User Commands telnet(1)
initial value for this toggle is
FALSE.
prettydump When the netdata toggle is enabled,
if prettydump is enabled, the output
from the netdata command will be
formatted in a more user readable
format. Spaces are put between each
character in the output. The begin-
ning of any TELNET escape sequence
is preceded by an asterisk (*) to
aid in locating them.
skiprc When the skiprc toggle is TRUE, TEL-
NET skips the reading of the .tel-
netrc file in the user's home direc-
tory when connections are opened.
The initial value for this toggle is
FALSE.
termdata Toggles the display of all terminal
data (in hexadecimal format). The
initial value for this toggle is
FALSE.
verboseencrypt When the verboseencrypt flag is
TRUE, TELNET prints out a message
each time encryption is enabled or
disabled. The initial value for this
toggle is FALSE.
? Display the legal toggle commands.
environ argument...
The environ command is used to manipulate variables that
may be sent through the TELNET ENVIRON option. The ini-
tial set of variables is taken from the users environ-
ment. Only the DISPLAY and PRINTER variables are
exported by default. Valid arguments for the environ
command are:
define variable value
Define variable to have a value of value. Any
SunOS 5.11 Last change: 17 Aug 2006 18
User Commands telnet(1)
variables defined by this command are automatically
exported. The value may be enclosed in single or
double quotes, so that tabs and spaces may be
included.
undefine variable
Remove variable from the list of environment vari-
ables.
export variable
Mark the variable to be exported to the remote side.
unexport variable
Mark the variable to not be exported unless expli-
citly requested by the remote side.
list
List the current set of environment variables. Those
marked with an asterisk (*) will be sent automati-
cally. Other variables will be sent only if expli-
citly requested.
?
Prints out help information for the environ command.
logout
Sends the telnet logout option to the remote side. This
command is similar to a close command. However, if the
remote side does not support the logout option, nothing
happens. If, however, the remote side does support the
logout option, this command should cause the remote side
to close the TELNET connection. If the remote side also
supports the concept of suspending a user's session for
later reattachment, the logout argument indicates that
the remote side should terminate the session immedi-
ately.
SunOS 5.11 Last change: 17 Aug 2006 19
User Commands telnet(1)
FILES
$HOME/.telnetrc file that contains commands to be exe-
cuted before initiating a telnet session
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE VALUE
Availability SUNWtnetc
SEE ALSO
rlogin(1), sh(1), stty(1), getlogin(3C), hosts(4),
krb5.conf(4), nologin(4), telnetrc(4), attributes(5),
inet(7P), inet6(7P)
DIAGNOSTICS
NO LOGINS: System going down in N minutes
The machine is in the process of being shut down and
logins have been disabled.
NOTES
On some remote systems, echo has to be turned off manually
when in "line by line" mode.
In "old line by line" mode, or LINEMODE, the terminal's EOF
character is only recognized (and sent to the remote system)
when it is the first character on a line.
The telnet protocol only uses single DES for session
protection-clients request service tickets with single DES
session keys. The KDC must know that host service principals
that offer the telnet service support single DES, which, in
practice, means that such principals must have single DES
keys in the KDC database.
SunOS 5.11 Last change: 17 Aug 2006 20
|
