.TH LISTEN 8
.SH NAME
listen, listen1, tcp7, tcp9, tcp19, tcp21, tcp22, tcp23, tcp25, tcp53, tcp110, tcp113, tcp143, tcp513, tcp515, tcp564, tcp565, tcp566, tcp567, tcp993, tcp995, tcp1723, tcp17007, tcp17008, tcp17009, tcp17010, tcp17013 \- listen for calls on a network device
.SH SYNOPSIS
.B aux/listen
.RB [ -iq ]
.RB [ -d
.IR srvdir ]
.RB [ -t
.IR trustsrvdir ]
.RB [ -n
.IR namespace ]
.RI [ net ]
.PP
.B aux/listen1
[
.B -tv
]
.I addr
.I cmd
[
.I args...
]
.SH DESCRIPTION
.I listen
listens on a network for inbound calls to local services.
.I Net
is the network protocol on which to listen, by default
.BR /net/tcp .
The services available are executable, non-empty files in
.I srvdir
or
.IR trustsrvdir .
If neither
.I srvdir
nor
.I trustsrvdir
is given,
.I listen
looks for executable files in
.BR /bin/service .
Services found in
.I srvdir
are executed as user
.BR none ;
services found in
.I trustsrvdir
are executed as the user who started
.IR listen .
When changing user to
.BR none ,
a new namespace is created,
usually by executing
.BR /lib/namespace ,
but
.B -n
selects an alternate
.IR namespace .
Option
.B -q
suppresses affirmative log information.
Option
.B -i
suppresses the periodic scan of the service directories for changes.
.PP
Service names are made by concatenating the name of
the network with the name of the service or port.
For example,
an inbound call on the TCP network for port 565 executes service
.BR tcp565 .
These programs are
.IR exec ed
with arguments consisting of
service
(e.g.,
.LR tcp25 ),
protocol
(e.g.,
.LR tcp ),
and the directory of this network connection,
with the network connection's
.B data
file bound to
.B /dev/cons
and opened read/write as file descriptors 0, 1 and 2.
.PP
At least the following services are available in
.BR /bin/service .
.TF \ tcp0000
.TP
.B tcp564
serve a piece of the name space using the Plan 9 file system protocol,
with authentication via
.I Tauth
(in
.IR attach (5)),
no encryption,
and multiplex multiple users on a single connection
(used by
.IR srv (4),
and also by Unix systems to see Plan 9 files).
.TP
.B tcp17007
serve a piece of the name space using the Plan 9 file system protocol,
with authentication at the start,
optional SSL encryption,
and no multiplexing of users
(typically used by
.IR cpu (1)
and
.IR import (4)).
Not usable by user
.IR none .
.TP
.B tcp17008
like
.BR tcp17007 ,
but serves the root of the tree,
forgoing the negotiation for which subtree to serve.
.TP
.B tcp17009
.I rx
remote execution.
.TP
.B tcp17010
server for
.IR cpu (1)
command.
.TP
.B tcp17013
server for old
.IR cpu (1)
command for compatibility with old clients.
.TP
.B tcp7
echo any bytes received (bit mirror)
.TP
.B tcp9
consume any bytes received (bit bucket)
.TP
.B tcp19
.B chargen
service.
.TP
.B tcp21
FTP daemon
.TP
.B tcp22
.IR ssh (1)
`secure shell' encrypted terminal connection or file transfer.
.TP
.B tcp23
.B telnet
terminal connection.
.TP
.B tcp25
mail delivery.
.TP
.B tcp53
TCP port for DNS.
.TP
.B tcp110
POP3 port.
.TP
.B tcp113
.B Ident
port (always reports
.BR none ).
.TP
.B tcp143
IMAP4rev1 port.
.TP
.B tcp513
.B rlogin
terminal connection.
.TP
.B tcp515
LP daemon; see
.IR lp (8).
.TP
.B tcp565
report the address of the incoming call.
.TP
.B tcp993
Secure IMAP4rev1 port.
.TP
.B tcp995
Secure POP3 port.
.TP
.B tcp1723
PPTP (point-to-point tunnelling protocol) service.
.PD
.PP
At least the following services are available in
.BR /bin/service.auth ,
the usual
.IR trustsrvdir .
.TF \ tcp0000
.TP
.B tcp566
validate a SecureNet box.
.TP
.B tcp567
Plan 9 authentication-ticket service.
.PD
.PP
.I Listen1
is a lightweight listener intended for personal use,
modeled from Inferno's
.\" write out this way so automatic programs
.\" don't try to make it into a real man page reference.
\fIlisten\fR(1).
.I Listen1
announces on
.IR address ,
running
.I cmd
.I args...
for each incoming connection;
the network directory is passed in the environment
as 
.BR $net .
Option
.B -t
causes
.I listen1
to run as the invoking user; the default
is to become
.B none
before listening.
Option
.B -v
causes verbose logging on standard output.
See
.B /rc/bin/tlssrvtunnel
for an example.
.SH FILES
.TF /env/sysname
.TP
.B /net/tcp
by convention, TCP device bind point
.SH SOURCE
.B /sys/src/cmd/aux/listen*.c
.br
.B /rc/bin/service*
.SH "SEE ALSO"
.IR authsrv (6),
.IR dial (2)
.SH BUGS
.IR Srvdir ,
.IR trustsrvdir
and
.I namespace
must all be absolute path names.