TELNETD(1M) — Series 300 and 800 Only

NAME

telnetd − TELNET protocol server

SYNOPSIS

/etc/telnetd

DESCRIPTION

Telnetd is a server for the DARPA standard TELNET virtual terminal protocol. The Internet daemon executes telnetd when it receives a service request at the port listed in the services data base for “telnet” using the “tcp” protocol; see inetd(1m) and services(4).

Telnetd operates by allocating a pseudo-terminal device (see pty(7)) for a client, then creating a login process which has the slave side of the pseudo-terminal as stdin, stdout, and stderr. Telnetd manipulates the master side of the pseudo-terminal, implementing the TELNET protocol and passing characters between the client and login process.

When a TELNET session is started up, telnetd sends a TELNET option to the client side indicating a willingness to do “remote echo” of characters. The pseudo-terminal allocated to the client is configured as a normal terminal is for login, with the exception of echoing characters (see tty(7)). Aside from this initial setup, the only mode changes telnetd carries out are those required for echoing characters at the client side of the connection.

To start telnetd from the Internet daemon, the configuration file /etc/inetd.conf must contain an entry as follows:

telnet stream tcp nowait root /etc/telnetd telnetd

DIAGNOSTICS

If any error is encountered by telnetd in establishing the connection, then an error message is returned through the connection, after which the connection is closed and the server exits. Any errors generated by the login process or its descendents are passed through as ordinary data.

All ptys on remote host in use
The server was unable to obtain a pseudo-terminal for use with the login process. Either all pseudo-terminals were in use or the pty driver has not been properly set up; see pty(4).

Next step: Check the pty configuration of the host where telnetd is executing.

fork: No more processes
Telnetd was unable to fork a process to handle the incoming connection.

Next step: Wait a period of time and try again. If this message persists, then the server’s host may have runaway processes that are using all the entries in the process table.

/bin/login: ...
The login program could not be started via exec(2) for the reason indicated.

DEPENDENCIES

Implemented on the Series 300 and 800 only.

AUTHOR

UCB (University of California at Berkeley)

Museum

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