NAME

telnetd - DARPA TELNET protocol server

SYNOPSIS

in.telnetd

DESCRIPTION

telnetd is a server which supports the DARPA standard TELNET virtual terminal protocol. telnetd is invoked by the internet server [see inetd(1M)], normally for requests to connect to the TELNET port as indicated by the /etc/services file [see services(4)].

telnetd operates by allocating a pseudo-terminal device for a client, then creating a login process which has the slave side of the pseudo-terminal as its standard input, output, and error. telnetd manipulates the master side of the pseudo-terminal, implementing the TELNET protocol and passing characters between the remote client and the login process.

When a TELNET session is started up,  telnetd  sends  TELNET
options  to  the  client side indicating a willingness to do
remote echo of characters, to  suppress  go  ahead,  and  to
receive  terminal  type  information from the remote client.
If the remote client is willing, the remote terminal type is
propagated  in the environment of the created login process.
The pseudo-terminal allocated to the client is configured to
operate  in  "cooked" mode, and with XTABS, ICRNL, and ONLCR
enabled                                                 [see
termio(4)].   telnetd  is  willing  to  do:   echo,  binary,
suppress        go         ahead,         and         timing
mark.
telnetd is willing to have the remote  client  do:   binary,
terminal type, and suppress go ahead.

SEE ALSO

telnet(1)

Postel, Jon, and Joyce Reynolds, ``Telnet Protocol  Specifi-
cation,''  RFC 854, Network Information Center, SRI Interna-
tional, Menlo Park, Calif., May 1983.

NOTES

Some TELNET commands are only partially implemented.

The TELNET protocol allows for the exchange of the number of lines and columns on the user's terminal, but telnetd doesn't make use of them.

Binary mode has no common interpretation except between similar operating systems

The terminal type name received from the remote client is converted to lower case.

The packet interface to the pseudo-terminal should be used for more intelligent flushing of input and output queues.

telnetd never sends TELNET go ahead commands.

telnetd can only support 64 pseudo-terminals.