protocol

The

command is used to communicate with another host using the

protocol. If

is invoked without the

argument, it enters command mode, indicated by its prompt

In this mode, it accepts and executes the commands listed below. If it is invoked with arguments, it performs an

command with those arguments.

Use IPv4 to connect to hosts.

Use IPv6 to connect to hosts.

Specifies an 8-bit data path. This causes an attempt to negotiate the

option on both input and output.

Specifies an 8-bit data path on output. This causes the BINARY option to be negotiated on output.

Sets the initial

escape character to

If

is omitted, then there will be no escape character.

Stops any character from being recognized as an escape character.

Attempt automatic login. Currently, this sends the user name via the

variable of the

option if supported by the remote system. The name used is that of the current user as returned by

if it agrees with the current user ID, otherwise it is the name associated with the user ID.

Specifies no automatic login to the remote system.

When connecting to the remote system, if the remote system understands the

option, then

will be sent to the remote system as the value for the variable USER. This option implies the

option. This option may also be used with the

command.

Opens

for recording trace information. See the

command below.

Specifies a user interface similar to

In this mode, the escape character is set to the tilde (~) character, unless modified by the -e option.

Disables the reading of the user's

file. (See the

command on this man page.)

Sets the initial value of the

toggle to

Turns on encryption of the data stream if possible.

Disables the

type of authentication.

If Kerberos authentication is being used, the

option requests that telnet obtain tickets for the remote host in realm realm instead of the remote host's realm, as determined by

Indicates the official name, an alias, or the Internet address of a remote host.

Indicates a port number (address of an application). If a number is not specified, the default

port is used.

When in rlogin mode, a line of the form ~. disconnects from the remote host; ~ is the telnet escape character. Similarly, the line ~^Z suspends the telnet session. The line ~^] escapes to the normal telnet escape prompt.

Once a connection has been opened,

will attempt to enable the

option. If this fails, then

will revert to one of two input modes: either character at a time or old line by line depending on what the remote system supports.

When

is enabled, 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 immediately 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 (this would mostly be used to enter passwords without the password being echoed).

If the

option is enabled, or if the

toggle is

(the default for old line by line; see below), the user's

and

characters are trapped locally, and sent as

protocol sequences to the remote side. If

has ever been enabled, then the user's

and

are also sent as

protocol sequences, and

is sent as a

instead of

There are options (see

and

below) which cause this action to flush subsequent output to the terminal (until the remote host acknowledges the

sequence) and flush previous terminal input (in the case of

and

While connected to a remote host,

command mode may be entered by typing the

escape character (initially ^]). When in command mode, the normal terminal editing conventions are available.

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

and

commands).

The auth command manipulates the information sent through the

option. Valid arguments for the auth command are as follows:

Disables the specified type of authentication. To obtain a list of available types, use the

command.

Enables the specified type of authentication. To obtain a list of available types, use the

command.

Lists the current status of the various types of authentication.

Close a

session and return to command mode.

Displays all, or some, of the

and

values (see below).

The encrypt command manipulates the information sent through the

option.

Note: Because of export controls, the

option is not supported outside of the United States and Canada.

Valid arguments for the encrypt command are as follows:

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

command.

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

command.

This is the same as the

command.

This is the same as the

command.

This is the same as the

command.

This is the same as the

command.

Attempts to start encryption. If you omit

and

both input and output are enabled. To obtain a list of available types, use the

command.

Lists the current status of encryption.

Stops encryption. If you omit input and output, encryption is on both input and output.

Sets the default type of encryption to be used with later

or

commands.

The

command is used to manipulate the the variables that my be sent through the

option. The initial set of variables is taken from the users environment, with only the

and

variables being exported by default. The

variable is also exported if the

or

options are used.
Valid arguments for the

command are:

Define the variable

to have a value of

Any variables defined by this command are automatically exported. The

may be enclosed in single or double quotes so that tabs and spaces may be included.

Remove

from the list of environment variables.

Mark the variable

to be exported to the remote side.

Mark the variable

to not be exported unless explicitly asked for by the remote side.

List the current set of environment variables. Those marked with a

will be sent automatically, other variables will only be sent if explicitly requested.

Prints out help information for the

command.

Sends the

option to the remote side. This command is similar to a

command; however, if the remote side does not support the

option, nothing happens. If, however, the remote side does support the

option, this command should cause the remote side to close the

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.

is one of several options, depending on the state of the

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.

Disable the

option, or, if the remote side does not understand the

option, then enter character at a time mode.

Enable the

option, or, if the remote side does not understand the

option, then attempt to enter old-line-by-line mode.

Attempt to enable (disable) the

mode of the

option. This requires that the

option be enabled.

Attempt to enable (disable) the

mode of the

option. This requires that the

option be enabled.

Attempt to enable (disable) the

mode of the

option. This requires that the

option be enabled.

Attempt to enable (disable) the

mode of the

option. This requires that the

option be enabled.

Prints out help information for the

command.

Open a connection to the named host. If no port number is specified,

will attempt to contact a

server at the default port. The host specification may be either a host name (see

or an Internet address specified in the dot notation (see

The

option may be used to specify the user name to be passed to the remote system via the

option. When connecting to a non-standard port,

omits any automatic initiation of

options. When the port number is preceded by a minus sign, the initial option negotiation is done. After establishing a connection, the file

in the users home directory is opened. Lines beginning with a # are comment lines. Blank lines are ignored. Lines that begin without white space 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 white space are assumed to be

commands and are processed as if they had been typed in manually to the

command prompt.

Close any open

session and exit

An end of file (in command mode) will also close a session and exit.

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):

Sends the

(Abort processes) sequence.

Sends the

(Abort Output) sequence, which should cause the remote system to flush all output

the remote system

the user's terminal.

Sends the

(Are You There) sequence, to which the remote system may or may not choose to respond.

Sends the

(Break) sequence, which may have significance to the remote system.

Sends the

(Erase Character) sequence, which should cause the remote system to erase the last character entered.

Sends the

(Erase Line) sequence, which should cause the remote system to erase the line currently being entered.

Sends the

(End Of File) sequence.

Sends the

(End of Record) sequence.

Sends the current

escape character (initially ^).

Sends the

(Go Ahead) sequence, which likely has no significance to the remote system.

If the remote side supports the

command,

will send the subnegotiation to request that the server send its current option status.

Sends the

(Interrupt Process) sequence, which should cause the remote system to abort the currently running process.

Sends the

(No OPeration) sequence.

Sends the

(SUSPend process) sequence.

Sends the

sequence. This sequence causes the remote system to discard all previously typed (but not yet read) input. This sequence is sent as

urgent data (and may not work if the remote system is a

system -- if it doesn't work, a lower case r may be echoed on the terminal).

Sends the

sequence.

can be either a decimal number between 0 and 255, or a symbolic name for a specific

command.

can also be either

or

to print out help information, including a list of known symbolic names.

Prints out help information for the

command.

The

command will set any one of a number of

variables to a specific value or to

The special value

turns off the function associated with the variable, this is equivalent to using the

command. The

command will disable or set to

any of the specified functions. The values of variables may be interrogated with the

command. The variables which may be set or unset, but not toggled, are listed here. In addition, any of the variables for the

command may be explicitly set or unset using the

and

commands.

If

is in localchars mode, or

is enabled, and the status character is typed, a

sequence (see

preceding) is sent to the remote host. The initial value for the "Are You There" character is the terminal's status character.

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).

If

is operating in

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 eof character is taken to be the terminal's

character.

If

is in

mode (see

below),

if

is operating in character at a time mode, then when this character is typed, a

sequence (see

above) is sent to the remote system. The initial value for the erase character is taken to be the terminal's

character.

This is the

escape character (initially ^[) which causes entry into

command mode (when connected to a remote system).

If

is in

mode (see

below) and the

character is typed, a

sequence (see

above) is sent to the remote host. The initial value for the flush character is taken to be the terminal's

character.

If

is operating in

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.

If

is in

mode (see

below) and the

character is typed, a

sequence (see

above) is sent to the remote host. The initial value for the interrupt character is taken to be the terminal's

character.

If

is in

mode (see

below),

if

is operating in character at a time mode, then when this character is typed, a

sequence (see

above) is sent to the remote system. The initial value for the kill character is taken to be the terminal's

character.

If

is operating in

or old line by line mode, then this character is taken to be the terminal's

character. The initial value for the lnext character is taken to be the terminal's

character.

If

is in

mode (see

below) and the

character is typed, a

sequence (see

above) is sent to the remote host. The initial value for the quit character is taken to be the terminal's

character.

If

is operating in

or old line by line mode, then this character is taken to be the terminal's

character. The initial value for the reprint character is taken to be the terminal's

character.

This is the rlogin escape character. If set, the normal

escape character is ignored unless it is preceded by this character at the beginning of a line. This character, at the beginning of a line followed by a "." closes the connection; when followed by a ^Z it suspends the telnet command. The initial state is to disable the rlogin escape character.

If the

option has been enabled, then this character is taken to be the terminal's

character. The initial value for the kill character is taken to be the terminal's

character.

If the

option has been enabled, then this character is taken to be the terminal's

character. The initial value for the kill character is taken to be the terminal's

character.

If

is in

mode, or

is enabled, and the

character is typed, a

sequence (see

above) is sent to the remote host. The initial value for the suspend character is taken to be the terminal's

character.

This is the file to which the output, caused by

or

tracing being

will be written. If it is set to

then tracing information will be written to standard output (the default).

If

is operating in

or old line by line mode, then this character is taken to be the terminal's

character. The initial value for the worderase character is taken to be the terminal's

character.

Displays the legal

commands.

The

command (Set Local Characters) is used to set or change the state of the the special characters when the

option has been enabled. Special characters are characters that get mapped to

commands sequences (like

or

or line editing characters (like

and

By default, the local special characters are exported.

Verify the current settings for the current special characters. The remote side is requested to send all the current special character settings, and if there are any discrepancies with the local side, the local side will switch to the remote value.

Switch to the local defaults for the special characters. The local default characters are those of the local terminal at the time when

was started.

Switch to the remote defaults for the special characters. The remote default characters are those of the remote system at the time when the

connection was established.

Prints out help information for the

command.

Show the current status of

This includes the peer one is connected to, as well as the current mode.

Toggle (between

and

various flags that control how

responds to events. These flags may be set explicitly to

or

using the

and

commands listed above. More than one argument may be specified. The state of these flags may be interrogated with the

command. Valid arguments are:

Turns on debugging information for the authentication code.

If

and

are both

then when the

or

characters are recognized (and transformed into

sequences; see

above for details),

refuses to display any data on the user's terminal until the remote system acknowledges (via a

option) that it has processed those

sequences. The initial value for this toggle is

if the terminal user had not done an "stty noflsh", otherwise

(see

When the

option is negotiated, by default the actual encryption (decryption) of the data stream does not start automatically. The autoencrypt (autodecrypt) command states that encryption of the output (input) stream should be enabled as soon as possible.

Note: Because of export controls, the

option is not supported outside the United States and Canada.

If the remote side supports the

option

attempts to use it to perform automatic authentication. If the

option is not supported, the user's login name are propagated through the

option. This command is the same as specifying

option on the

command.

If

and

are both

then when either the

or

characters is typed (see

above for descriptions of the

and

characters), the resulting

sequence sent is followed by the

sequence. This procedure

cause the remote system to begin throwing away all previously typed input until both of the

sequences have been read and acted upon. The initial value of this toggle is

Enable or disable the

option on both input and output.

Enable or disable the

option on input.

Enable or disable the

option on output.

If this is

then carriage returns will be sent as

If this is

then carriage returns will be send as

The initial value for this toggle is

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

Toggles socket level debugging (useful only to the

The initial value for this toggle is

Turns on debugging information for the encryption code.

If this is

then the

and

characters (see

above) are recognized locally, and transformed into (hopefully) appropriate

control sequences (respectively

and

see

above). The initial value for this toggle is

in old line by line mode, and

in character at a time mode. When the

option is enabled, the value of

is ignored, and assumed to always be

If

has ever been enabled, then

is sent as

and

are sent as

see

above).

Toggles the display of all network data (in hexadecimal format). The initial value for this toggle is

Toggles the display of some internal

protocol processing (having to do with

options). The initial value for this toggle is

When the

toggle is enabled, if

is enabled the output from the

command will be formatted in a more user readable format. Spaces are put between each character in the output, and the beginning of any

escape sequence is preceded by a '*' to aid in locating them.

When the skiprc toggle is

skips the reading of the

file in the users home directory when connections are opened. The initial value for this toggle is

Toggles the display of all terminal data (in hexadecimal format). The initial value for this toggle is

When the

toggle is

prints out a message each time encryption is enabled or disabled. The initial value for this toggle is

Note: Because of export controls, data encryption is not supported outside of the United States and Canada.

Displays the legal

commands.

Suspend

This command only works when the user is using the

Execute a single command in a subshell on the local system. If

is omitted, then an interactive subshell is invoked.

Get help. With no arguments,

prints a help summary. If a command is specified,

will print the help information for just that command.

uses at least the

and

environment variables. Other environment variables may be propagated to the other side via the

option.

user customized telnet startup values

The

command appeared in

On some remote systems, echo has to be turned off manually when in old line by line mode.

In old line by line mode or

the terminal's

character is only recognized (and sent to the remote system) when it is the first character on a line.