The
program is a server which supports the
interactive communication protocol.
is normally invoked by the internet server (see
for requests to connect to the
port as indicated by the
file (see
The
option may be used to start up
manually, instead of through
If started up this way,
may be specified to run
on an alternate
port number.
The
program accepts the following options:
This option may be used for specifying what mode should
be used for authentication.
Note that this option is only useful if
has been compiled with support for authentication, which is not
available in the current version. The following values of
are understood:
Turns on authentication debugging code.
Only allow connections when the remote user can provide valid
authentication information to identify the remote user, and is allowed
access to the specified account without providing a password.
Only allow connections when the remote user can provide valid
authentication information to identify the remote user. The
command will provide any additional user verification needed if the
remote user is not allowed automatic access to the specified account.
Only allow connections that supply some authentication information.
This option is currently not supported by any of the existing
authentication mechanisms, and is thus the same as specifying
This is the default state. Authentication information is not
required. If no or insufficient authentication information is
provided, then the
program will provide the necessary user verification.
This disables the authentication code. All user verification will
happen through the
program.
This option may be used for debugging purposes. This allows
to print out debugging information to the connection, allowing the
user to see what
is doing. There are several possible values for
Prints information about the negotiation of
options.
Prints the
information, plus some additional information about what processing is
going on.
Displays the data stream received by
Displays data written to the pty.
Has not been implemented yet.
If
has been compiled with support for encryption, then the
option may be used to enable encryption debugging code.
Disables the printing of host-specific information before
login has been completed.
This option may be used to specify a different login program.
By default,
is used.
Disable
keep-alives. Normally
enables the
keep-alive mechanism to probe connections that
have been idle for some period of time to determine
if the client is still there, so that idle connections
from machines that have crashed or can no longer
be reached may be cleaned up.
This option is only enabled if
is compiled with support for
cards.
It causes the
option to be passed on to
and thus is only useful if
supports the
flag to indicate that only
validated logins are allowed. This is usually useful for controlling
remote logins from outside of a firewall.
Sets the IP type-of-service (TOS) option for the telnet
connection to the value
This option is only valid if
has been built with support for the authentication option.
It disables the use of
authentication, and
can be used to temporarily disable
a specific authentication type without having to recompile
If the file
is present,
will display its contents before the login prompt of a telnet session (see
operates by allocating a pseudo-terminal device (see
for a client, then creating a login process which has
the slave side of the pseudo-terminal as
and
manipulates the master side of the pseudo-terminal,
implementing the
protocol and passing characters
between the remote client and the login process.
When a
session is started up,
sends
options to the client side indicating
a willingness to do the
following
options, which are described in more detail below:
DO AUTHENTICATION
WILL ENCRYPT
DO TERMINAL TYPE
DO TSPEED
DO XDISPLOC
DO NEW-ENVIRON
DO ENVIRON
WILL SUPPRESS GO AHEAD
DO ECHO
DO LINEMODE
DO NAWS
WILL STATUS
DO LFLOW
DO TIMING-MARK
The pseudo-terminal allocated to the client is configured
to operate in (lqcooked(rq mode, and with
enabled (see
has support for enabling locally the following
options:
When the
option is enabled, a
or
will be sent to the client to indicate the
current state of terminal echoing.
When terminal echo is not desired, a
is sent to indicate that
will take care of echoing any data that needs to be
echoed to the terminal, and then nothing is echoed.
When terminal echo is desired, a
is sent to indicate that
will not be doing any terminal echoing, so the
client should do any terminal echoing that is needed.
Indicates that the client is willing to send a
8 bits of data, rather than the normal 7 bits
of the Network Virtual Terminal.
Indicates that it will not be sending
go ahead, commands.
Indicates a willingness to send the client, upon
request, of the current status of all
options.
Whenever a
command is received, it is always responded
to with a
When a
is received, a
is sent in response, and the
session is shut down.
Only sent if
is compiled with support for data encryption, and
indicates a willingness to decrypt
the data stream.
has support for enabling remotely the following
options:
Sent to indicate that
is willing to receive an 8 bit data stream.
Requests that the client handle flow control
characters remotely.
This is not really supported, but is sent to identify a 4.2BSD
client, which will improperly respond with
If a
is received, a
will be sent in response.
Indicates a desire to be able to request the
name of the type of terminal that is attached
to the client side of the connection.
Indicates that it does not need to receive
the go ahead command.
Requests that the client inform the server when
the window (display) size changes.
Indicates a desire to be able to request information
about the speed of the serial line to which
the client is attached.
Indicates a desire to be able to request the name
of the X windows display that is associated with
the telnet client.
Indicates a desire to be able to request environment
variable information, as described in RFC 1572.
Indicates a desire to be able to request environment
variable information, as described in RFC 1408.
Only sent if
is compiled with support for linemode, and
requests that the client do line by line processing.
Only sent if
is compiled with support for both linemode and
kludge linemode, and the client responded with
If the client responds with
the it is assumed that the client supports
kludge linemode.
Note that the
option can be used to disable this.
Only sent if
is compiled with support for authentication, and
indicates a willingness to receive authentication
information for automatic login.
Only sent if
is compiled with support for data encryption, and
indicates a willingness to decrypt
the data stream.
FILES
"SEE ALSO"
STANDARDS
PROTOCOL SPECIFICATION
TELNET OPTION SPECIFICATIONS
TELNET BINARY TRANSMISSION
TELNET ECHO OPTION
TELNET SUPPRESS GO AHEAD OPTION
TELNET STATUS OPTION
TELNET TIMING MARK OPTION
TELNET EXTENDED OPTIONS - LIST OPTION
TELNET END OF RECORD OPTION
Telnet Window Size Option
Telnet Terminal Speed Option
Telnet Terminal-Type Option
Telnet X Display Location Option
Requirements for Internet Hosts -- Application and Support
Telnet Linemode Option
Telnet Remote Flow Control Option
Telnet Authentication Option
Telnet Authentication: Kerberos Version 4
Telnet Authentication: SPX
Telnet Environment Option Interoperability Issues
Telnet Environment Option
BUGS
Some
commands are only partially implemented.
Because of bugs in the original 4.2 BSD
performs some dubious protocol exchanges to try to discover if the remote
client is, in fact, a 4.2 BSD
Binary mode
has no common interpretation except between similar operating systems
(Unix in this case).
The terminal type name received from the remote client is converted to
lower case.
never sends
(go ahead) commands.
The source code is not comprehensible.
