telnet.1.txt

经典的unix下telnet的c代码

command; however, if the remote side does not support the
.Dv LOGOUT
option, nothing happens.
If, however, the remote side does support the
.Dv LOGOUT
option, this command should cause the remote side to close the
.Tn TELNET
connection.
If the remote side also supports the concept of
suspending a user's session for later reattachment,
the logout argument indicates that you
should terminate the session immediately.
.It Ic mode Ar type
.Ar type
is one of several options, depending on the state of the
.Tn TELNET
session.
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.
.Bl -tag -width Ar
.It Ic character
Disable the
.Dv TELNET LINEMODE
option, or, if the remote side does not understand the
.Dv LINEMODE
option, then enter ``character at a time'' mode.
.It Ic line
Enable the
.Dv TELNET LINEMODE
option, or, if the remote side does not understand the
.Dv LINEMODE
option, then attempt to enter ``old-line-by-line'' mode.
.It Ic isig Pq Ic \-isig
Attempt to enable (disable) the
.Dv TRAPSIG
mode of the
.Dv LINEMODE
option.
This requires that the
.Dv LINEMODE
option be enabled.
.It Ic edit Pq Ic \-edit
Attempt to enable (disable) the
.Dv EDIT
mode of the
.Dv LINEMODE
option.
This requires that the
.Dv LINEMODE
option be enabled.
.It Ic softtabs Pq Ic \-softtabs
Attempt to enable (disable) the
.Dv SOFT_TAB
mode of the
.Dv LINEMODE
option.
This requires that the
.Dv LINEMODE
option be enabled.
.It Ic litecho Pq Ic \-litecho
Attempt to enable (disable) the
.Dv LIT_ECHO
mode of the
.Dv LINEMODE
option.
This requires that the
.Dv LINEMODE
option be enabled.
.It Ic \&?
Prints out help information for the
.Ic mode
command.
.El
.It Xo
.Ic open Ar host
.Op Fl l Ar user
.Oo Op Fl
.Ar port Oc
.Xc
Open a connection to the named host.
If no port number
is specified,
.Nm
will attempt to contact a
.Tn TELNET
server at the default port.
The host specification may be either a host name (see
.Xr hosts 5 )
or an Internet address specified in the ``dot notation'' (see
.Xr inet 3 ) .
The
.Fl l
option may be used to specify the user name
to be passed to the remote system via the
.Ev ENVIRON
option.
When connecting to a non-standard port,
.Nm
omits any automatic initiation of
.Tn TELNET
options.
When the port number is preceded by a minus sign,
the initial option negotiation is done.
After establishing a connection, the file
.Pa \&.telnetrc
in the
user's home directory is opened.
Lines beginning with a ``#'' are
comment lines.
Blank lines are ignored.
Lines that begin
without whitespace are the start of a machine entry.
The first thing on the line is the name of the machine that is
being connected to.
The rest of the line, and successive
lines that begin with whitespace are assumed to be
.Nm
commands and are processed as if they had been typed
in manually to the
.Nm
command prompt.
.It Ic quit
Close any open
.Tn TELNET
session and exit
.Nm telnet .
An end-of-file (in command mode) will also close a session and exit.
.It Ic send Ar arguments
Sends one or more special character sequences to the remote host.
The following are the arguments which may be specified
(more than one argument may be specified at a time):
.Bl -tag -width escape
.It Ic abort
Sends the
.Dv TELNET ABORT
(Abort
processes)
sequence.
.It Ic ao
Sends the
.Dv TELNET AO
(Abort Output) sequence, which should cause the remote system to flush
all output
.Em from
the remote system
.Em to
the user's terminal.
.It Ic ayt
Sends the
.Dv TELNET AYT
(Are You There)
sequence, to which the remote system may or may not choose to respond.
.It Ic brk
Sends the
.Dv TELNET BRK
(Break) sequence, which may have significance to the remote
system.
.It Ic ec
Sends the
.Dv TELNET EC
(Erase Character)
sequence, which should cause the remote system to erase the last character
entered.
.It Ic el
Sends the
.Dv TELNET EL
(Erase Line)
sequence, which should cause the remote system to erase the line currently
being entered.
.It Ic eof
Sends the
.Dv TELNET EOF
(End Of File)
sequence.
.It Ic eor
Sends the
.Dv TELNET EOR
(End of Record)
sequence.
.It Ic escape
Sends the current
.Nm
escape character (initially ``^]'').
.It Ic ga
Sends the
.Dv TELNET GA
(Go Ahead)
sequence, which likely has no significance to the remote system.
.It Ic getstatus
If the remote side supports the
.Dv TELNET STATUS
command,
.Ic getstatus
will send the subnegotiation to request that the server send
its current option status.
.It Ic ip
Sends the
.Dv TELNET IP
(Interrupt Process) sequence, which should cause the remote
system to abort the currently running process.
.It Ic nop
Sends the
.Dv TELNET NOP
(No OPeration)
sequence.
.It Ic susp
Sends the
.Dv TELNET SUSP
(SUSPend process)
sequence.
.It Ic synch
Sends the
.Dv TELNET SYNCH
sequence.
This sequence causes the remote system to discard all previously typed
(but not yet read) input.
This sequence is sent as
.Tn TCP
urgent
data (and may not work if the remote system is a
.Bx 4.2
system -- if
it doesn't work, a lower case ``r'' may be echoed on the terminal).
.It Ic do Ar cmd
Sends the
.Dv TELNET DO
.Ar cmd
sequence.
.Ar cmd
can be either a decimal number between 0 and 255,
or a symbolic name for a specific
.Dv TELNET
command.
.Ar cmd
can also be either
.Ic help
or
.Ic ?\&
to print out help information, including
a list of known symbolic names.
.It Ic dont Ar cmd
Sends the
.Dv TELNET DONT
.Ar cmd
sequence.
.Ar cmd
can be either a decimal number between 0 and 255,
or a symbolic name for a specific
.Dv TELNET
command.
.Ar cmd
can also be either
.Ic help
or
.Ic ?\&
to print out help information, including
a list of known symbolic names.
.It Ic will Ar cmd
Sends the
.Dv TELNET WILL
.Ar cmd
sequence.
.Ar cmd
can be either a decimal number between 0 and 255,
or a symbolic name for a specific
.Dv TELNET
command.
.Ar cmd
can also be either
.Ic help
or
.Ic ?\&
to print out help information, including
a list of known symbolic names.
.It Ic wont Ar cmd
Sends the
.Dv TELNET WONT
.Ar cmd
sequence.
.Ar cmd
can be either a decimal number between 0 and 255,
or a symbolic name for a specific
.Dv TELNET
command.
.Ar cmd
can also be either
.Ic help
or
.Ic ?\&
to print out help information, including
a list of known symbolic names.
.It Ic \&?
Prints out help information for the
.Ic send
command.
.El
.It Ic set Ar argument value
.It Ic unset Ar argument value
The
.Ic set
command will set any one of a number of
.Nm
variables to a specific value or to
.Dv TRUE .
The special value
.Ic off
turns off the function associated with
the variable; this is equivalent to using the
.Ic unset
command.
The
.Ic unset
command will disable or set to
.Dv FALSE
any of the specified functions.
The values of variables may be interrogated with the
.Ic display
command.
The variables which may be set or unset, but not toggled, are
listed here.
In addition, any of the variables for the
.Ic toggle
command may be explicitly set or unset using
the
.Ic set
and
.Ic unset
commands.
.Bl -tag -width escape
.It Ic ayt
If
.Tn TELNET
is in
.Ic localchars
mode, or
.Dv LINEMODE
is enabled, and the status character is typed, a
.Dv TELNET AYT
sequence (see
.Ic send ayt
preceding) is sent to the
remote host.
The initial value for the "Are You There"
character is the terminal's status character.
.It Ic 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
echoing of entered characters (for entering, say, a password).
.It Ic eof
If
.Nm
is operating in
.Dv LINEMODE
or ``old 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
.Ic eof
character is taken to be the terminal's
.Ic eof
character.
.It Ic erase
If
.Nm
is in
.Ic localchars
mode (see
.Ic toggle
.Ic localchars
below),
and if
.Nm
is operating in ``character at a time'' mode, then when this
character is typed, a
.Dv TELNET EC
sequence (see
.Ic send
.Ic ec
above)
is sent to the remote system.
The initial value for the
.Ic erase
character is taken to be
the terminal's
.Ic erase
character.
.It Ic escape
This is the
.Nm
escape character (initially ``^['') which causes entry
into
.Nm
command mode (when connected to a remote system).
.It Ic flushoutput
If
.Nm
is in
.Ic localchars
mode (see
.Ic toggle
.Ic localchars
below)
and the
.Ic flushoutput
character is typed, a
.Dv TELNET AO
sequence (see
.Ic send
.Ic ao
above)
is sent to the remote host.
The initial value for the
.Ic flush
character is taken to be
the terminal's
.Ic flush
character.
.It Ic forw1
.It Ic forw2
If
.Tn TELNET
is operating in
.Dv LINEMODE ,
these are the
characters that, when typed, cause partial lines to be
forwarded to the remote system.
The initial value for
the forwarding characters are taken from the terminal's
eol and eol2 characters.
.It Ic interrupt
If
.Nm
is in
.Ic localchars
mode (see
.Ic toggle
.Ic localchars
below)
and the
.Ic interrupt
character is typed, a
.Dv TELNET IP
sequence (see
.Ic send
.Ic ip
above)
is sent to the remote host.
The initial value for the
.Ic interrupt
character is taken to be
the terminal's
.Ic intr
character.
.It Ic kill
If
.Nm
is in
.Ic localchars
mode (see
.Ic toggle
.Ic localchars
below),
and if
.Nm
is operating in ``character at a time'' mode, then when this
character is typed, a
.Dv TELNET EL
sequence (see
.Ic send
.Ic el
above)
is sent to the remote system.
The initial value for the
.Ic kill
character is taken to be
the terminal's
.Ic kill
character.
.It Ic lnext
If
.Nm
is operating in
.Dv LINEMODE
or ``old line by line'' mode, then this character is taken to
be the terminal's
.Ic lnext
character.
The initial value for the
.Ic lnext
character is taken to be
the terminal's
.Ic lnext
character.
.It Ic quit
If
.Nm
is in
.Ic localchars
mode (see
.Ic toggle
.Ic localchars
below)