LISTEN(8) LISTEN(8)
NAME
listen, listen1, tcp7, tcp9, tcp19, tcp21, tcp23, tcp25,
tcp53, tcp110, tcp113, tcp143, tcp445, tcp513, tcp515,
tcp564, tcp565, tcp566, tcp567, tcp993, tcp995, tcp1723,
tcp17019, tcp17020 - listen for calls on a network device
SYNOPSIS
aux/listen [-iq] [-d srvdir] [-t trustsrvdir] [-n namespace]
[-p maxprocs] [-o copt] [-O sopt] [-a addr] [proto]
aux/listen1 [ -1tv ] [-n namespace] [-p maxprocs] [-o copt]
[-O sopt] addr cmd [ args... ]
DESCRIPTION
Listen listens on a network for inbound calls to local ser-
vices. Proto is the network protocol on which to listen, by
default tcp. Incoming calls to any address * are accepted
unless addr is specified with the -a option. The services
available are executable, non-empty files in srvdir or
trustsrvdir. If neither srvdir nor trustsrvdir is given,
listen looks for executable files in /bin/service. Services
found in srvdir are executed as user none; services found in
trustsrvdir are executed as the user who started listen.
When changing user to none, a new namespace is created, usu-
ally by executing /lib/namespace, but -n selects an alter-
nate namespace. The -p option limits the number of processes
that listen spawns to service the connections. If the
maxprocs limit is reached, listen will log the event and
delay servicing until the number of connection processes
drops below the limit again. A maxprocs smaller or equal
zero means no limit (default). The -o and -O options cause
protocol-specific control messages to be written to the con-
trol file of the listening server connection -O or the
incoming client connection -o. They can be specified multi-
ple times. See ip(3) for details. Option -q suppresses
affirmative log information. Option -i suppresses the peri-
odic scan of the service directories for changes.
Service names are made by concatenating the name of the net-
work with the name of the service or port. For example, an
inbound call on the TCP network for port 565 executes ser-
vice tcp565.
Services may have individual namespace(6) files specified
within srvdir. If provided, the namespace is used as the
parent for each connection to the corresponding service.
Namespace files are found by appending a .namespace suffix
to the service name.
At least the following services are available in
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LISTEN(8) LISTEN(8)
/bin/service.
tcp564 serve a piece of the name space using the Plan 9
file system protocol, with authentication via
Tauth (in attach(5)), no encryption, and multiplex
multiple users on a single connection (used by
srv(4), and also by Unix systems to see Plan 9
files).
tcp17019 server for rcpu(1), replaces rx, import and cpu
using TLS for encryption.
tcp17020 TLS encrypted 9P fileserver (t9fs) for srvtls (see
srv(4)).
tcp7 echo any bytes received (bit mirror)
tcp9 consume any bytes received (bit bucket)
tcp19 chargen service.
tcp21 FTP daemon
tcp23 telnet terminal connection.
tcp25 mail delivery.
tcp53 TCP port for DNS.
tcp110 POP3 port.
tcp113 Ident port (always reports none).
tcp143 IMAP4rev1 port.
tcp445 CIFS/SMB file sharing.
tcp513 rlogin terminal connection.
tcp515 LP daemon; see lp(8).
tcp565 report the address of the incoming call.
tcp993 Secure IMAP4rev1 port.
tcp995 Secure POP3 port.
tcp1723 PPTP (point-to-point tunnelling protocol) service.
At least the following services are available in
/bin/service.auth, the usual trustsrvdir.
tcp566 validate a SecureNet box.
tcp567 Plan 9 authentication-ticket service.
Listen1 is a lightweight listener intended for personal use,
modeled from Inferno's listen(1). It announces on address,
running cmd args... for each incoming connection; the net-
work directory is passed in the environment as $net. Option
-t causes listen1 to run as the invoking user; the default
is to become none before listening. Option -1 arms a one-
shot listener; it terminates listen1 upon receiving a single
call. Option -v causes verbose logging on standard output.
See /rc/bin/tlssrvtunnel for an example.
FILES
/net/tcp by convention, TCP device bind point
SOURCE
/sys/src/cmd/aux/listen*.c
/rc/bin/service*
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LISTEN(8) LISTEN(8)
SEE ALSO
authsrv(6), dial(2), ip(3)
BUGS
Srvdir, trustsrvdir and namespace must all be absolute path
names.
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