telnetd - protocol server [-a authmode] [-B] [-D] [debugmode] [-edebug] [-h] [-Iinitid] [-l] [-k] [-n] [-rlowpty-highpty] [-s] [-S tos] [-u len] [-U] [-X authtype] [-debug [port]] [--version]

DESCRIPTION
The command is a server which supports the standard virtual terminal 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 command accepts the following options: -a authmode 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 the option. There are several valid values for 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. Encryption is required. This should be used in conjunction with one of the other authentication options and is probably not useful alone. This disables the authentication code. All user verification will happen through the program. Specifies bftp server mode. In this mode, causes login to start a session rather than the user's normal shell. In bftp daemon mode, normal logins are not supported, and it must be used on a port other than the normal port. -D debugmode 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. Enables debugging on each socket created by (see in If has been compiled with support for data encryption, then the option may be used to enable encryption debugging code. Disables the printing of host-specific information before login has been completed. -I initid This option is only applicable to systems prior to 7.0. It specifies the from to use when init starts login sessions. The default is fe. This option is only useful if has been compiled with both linemode and kludge linemode support. If the option is specified, then if the remote client does not support the option, then will operate in character at a time mode. It will still support kludge linemode, but will only go into kludge linemode if the remote client requests it. (This is done by by the client sending and The option is most useful when there are remote clients that do not support kludge linemode, but pass the heuristic (if they respond with in response to a for kludge linemode support. Specifies line mode. Tries to force clients to use line-at-a-time mode. If the option is not supported, it will go into kludge linemode. 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. -r lowpty-highpty This option is only enabled when is compiled for It specifies an inclusive range of pseudo-terminal devices to use. If the system has sysconf variable configured, the default pty search range is 0 to otherwise, the default range is 0 to 128. Either or may be omitted to allow changing either end of the search range. If is omitted, the - character is still required so that can differentiate from This option is only enabled if is compiled with support for SecurID cards. It causes the option to be passed on to and thus is only useful if supports the flag to indicate that only SecurID validated logins are allowed, and is usually useful for controlling remote logins from outside of a firewall. -S tos -u len This option is used to specify the size of the field in the structure that holds the remote host name. If the resolved host name is longer than the dotted decimal value will be used instead. This allows hosts with very long host names that overflow this field to still be uniquely identified. Specifying indicates that only dotted decimal addresses should be put into the file. This option causes to refuse connections from addresses that cannot be mapped back into a symbolic name via the routine. -X authtype 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 Prints out the KerbNet release version of the binary and then exits. 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 “cooked” mode, and with and 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.
(UNICOS systems only)
(if supported)
(if supported) (if supported) TELNET 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 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.