TELNET(1C) RISC/os Reference Manual TELNET(1C)
NAME
telnet - user interface to the TELNET protocol
SYNOPSIS
telnet [ host [ port ] ]
DESCRIPTION
telnet is used to communicate 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 the commands listed
below. If it is invoked with arguments, it performs an open
command (see below) with those arguments.
Once a connection has been opened, telnet enters an input
mode. The input mode entered will be either "character at a
time" or "line by line" depending on what the remote system
supports.
In "character at a time" mode, most text typed is immedi-
ately sent to the remote host for processing.
In "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 (this would mostly be used to
enter passwords without the password being echoed).
In either mode, if the localchars toggle is TRUE (the
default in line mode; see below), the user's quit, intr, and
flush characters are trapped locally, and sent as TELNET
protocol sequences to the remote side. There are options
(see toggle autoflush and toggle autosynch below) which
cause this action to flush subsequent output to the terminal
(until the remote host acknowledges the TELNET sequence) and
flush previous terminal input (in the case of quit and
intr).
While connected to a remote host, telnet command mode may be
entered by typing the telnet "escape character" (initially
"^]"). When in command mode, the normal terminal editing
conventions are available.
Commands
The following commands are available. Only enough of each
command to uniquely identify it need be typed (this is also
true for arguments to the mode, set, toggle, and display
commands).
open host [ port ] Open a connection to the named host. If
no port number is specified, telnet will
attempt to contact a TELNET server at
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the default port. The host specifica-
tion may be either a host name (see
hosts(4)) or an Internet address speci-
fied in the "dot notation" (see
inet(3N)).
close Close a TELNET session and return to
command mode.
quit Close any open TELNET session and exit
telnet. An end of file (in command
mode) will also close a session and
exit.
z Suspend telnet. This command only works
when the user is using the csh(1).
mode type type is either line (for "line by line"
mode) or character (for "character at a
time" mode). The remote host is asked
for permission to go into the requested
mode. If the remote host is capable of
entering that mode, the requested mode
will be entered.
status Show the current status of telnet. This
includes the peer one is connected to,
as well as the current mode.
display [ argument... ]
Displays all, or some, of the set and
toggle values (see below).
? [ 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 arguments Sends one or more special character
sequences to the remote host. The fol-
lowing are the arguments which may be
specified (more than one argument may be
specified at a time):
escape
Sends the current telnet escape
character (initially "^]").
synch
Sends the TELNET SYNCH sequence.
This sequence causes the remote
system to discard all previously
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typed (but not yet read) input.
This sequence is sent as TCP urgent
data (and may not work if the
remote system is a 4.2 BSD system
-- if it doesn't work, a lower case
"r" may be echoed on the terminal).
brk Sends the TELNET BRK (Break)
sequence, which may have signifi-
cance to the remote system.
ip Sends the TELNET IP (Interrupt Pro-
cess) sequence, which should cause
the remote system to abort the
currently running process.
ao Sends the TELNET AO (Abort Output)
sequence, which should cause the
remote system to flush all output
from the remote system to the
user's terminal.
ayt Sends the TELNET AYT (Are You
There) sequence, to which the
remote system may or may not choose
to respond.
ec Sends the TELNET EC (Erase Charac-
ter) sequence, which should cause
the remote system to erase the last
character entered.
el Sends the TELNET EL (Erase Line)
sequence, which should cause the
remote system to erase the line
currently being entered.
ga Sends the TELNET GA (Go Ahead)
sequence, which likely has no sig-
nificance to the remote system.
nop Sends the TELNET NOP (No OPeration)
sequence.
? Prints out help information for the
send command.
set argument value Set any one of a number of telnet vari-
ables to a specific value. The special
value "off" turns off the function asso-
ciated with the variable. The values of
variables may be interrogated with the
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display command. The variables which
may be specified are:
echo This is the value (initially "^E")
which, when in "line by line" mode,
toggles between doing local echoing
of entered characters (for normal
processing), and suppressing echo-
ing of entered characters (for
entering, say, a password).
escape
This is the telnet escape character
(initially "^[") which causes entry
into telnet command mode (when con-
nected to a remote system).
interrupt
If telnet is in localchars mode
(see toggle localchars below) and
the interrupt character is typed, a
TELNET IP sequence (see send ip
above) is sent to the remote host.
The initial value for the interrupt
character is taken to be the
terminal's intr character.
quit If telnet is in localchars mode
(see toggle localchars below) and
the quit character is typed, a TEL-
NET BRK sequence (see send brk
above) 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
(see toggle localchars below) and
the flushoutput character is typed,
a TELNET AO sequence (see send ao
above) is sent to the remote host.
The initial value for the flush
character is taken to be the
terminal's flush character.
erase
If telnet is in localchars mode
(see toggle localchars below), and
if telnet is operating in "charac-
ter at a time" mode, then when this
character is typed, a TELNET EC
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sequence (see send ec above) is
sent to the remote system. The
initial value for the erase charac-
ter is taken to be the terminal's
erase character.
kill If telnet is in localchars mode
(see toggle localchars below), and
if telnet is operating in "charac-
ter at a time" mode, then when this
character is typed, a TELNET EL
sequence (see send el above) is
sent to the remote system. The
initial value for the kill charac-
ter is taken to be the terminal's
kill character.
eof If telnet is operating in "line by
line" mode, entering this character
as the first character on a line
will cause this character to be
sent to the remote system. The
initial value of the eof character
is taken to be the terminal's eof
character.
toggle arguments... Toggle (between TRUE and FALSE) 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 arguments are:
localchars
If this is TRUE, then the flush,
interrupt, quit, erase, and kill
characters (see set above) are
recognized locally, and transformed
into (hopefully) appropriate TELNET
control sequences (respectively ao,
ip, brk, ec, and el; see send
above). The initial value for this
toggle is TRUE in "line by line"
mode, and FALSE in "character at a
time" mode.
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 above for
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details), telnet refuses to display
any data on the user's terminal
until the remote system ack-
nowledges (via a TELNET timing Mark
option) that it has processed those
TELNET sequences. The initial
value for this toggle is TRUE if
the terminal user had not done an
"stty noflsh", otherwise FALSE (see
stty(1)).
autosynch
If autosynch and localchars are
both TRUE, then when either the
intr or quit characters is typed
(see set above for descriptions of
the intr and quit characters), the
resulting TELNET sequence sent is
followed by the TELNET SYNCH
sequence. This procedure should
cause the remote system to begin
throwing away all previously typed
input until both of the TELNET
sequences have been read and acted
upon. The initial value of this
toggle is FALSE.
crmod
Toggle carriage return mode. When
this mode is enabled, most carriage
return characters received from the
remote host will be mapped into a
carriage 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 not very useful
unless the remote host only sends
carriage return, but never line
feed. The initial value for this
toggle is FALSE.
debug
Toggles socket level debugging
(useful only to the superuser).
The initial value for this toggle
is FALSE.
options
Toggles the display of some inter-
nal telnet protocol processing
(having to do with TELNET options).
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The initial value for this toggle
is FALSE.
netdata
Toggles the display of all network
data (in hexadecimal format). The
initial value for this toggle is
FALSE.
? Displays the legal toggle commands.
ERRORS
There is no adequate way for dealing with flow control.
On some remote systems, echo has to be turned off manually
when in "line by line" mode.
There is enough settable state to justify a .telnetrc file.
No capability for a .telnetrc file is provided.
In "line by line" mode, the terminal's eof character is only
recognized (and sent to the remote system) when it is the
first character on a line.
ORIGIN
4.3 BSD
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