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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, tcp17007, tcp17008, tcp17009, tcp17010, tcp17013, tcp17019, tcp17020 – listen for calls on a network device

SYNOPSIS

aux/listen [-iq] [-d srvdir] [-t trustsrvdir] [-n namespace] [-p maxprocs] [-a addr] [proto]

aux/listen1 [ -1tv ] [-p maxprocs] [-n namespace] addr cmd [ args... ]

DESCRIPTION

Listen listens on a network for inbound calls to local services. 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, usually by executing /lib/namespace, but -n selects an alternate 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). Option -q suppresses affirmative log information. Option -i suppresses the periodic scan of the service directories for changes.

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 tcp565.

At least the following services are available in /bin/service.

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).  

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 cpu(1) and import(4)). Not usable by user none.  

like tcp17007, but serves the root of the tree, forgoing the negotiation for which subtree to serve.  

rx remote execution.  

server for cpu(1) command.  

server for old cpu(1) command for compatibility with old clients.  

server for rcpu(1), replaces rx, import(4) and cpu(1) using TLS for encryption.  

TLS encrypted 9P fileserver (t9fs) for srvtls (see srv(4)).  

echo any bytes received (bit mirror)  

consume any bytes received (bit bucket)  

chargen service.  

FTP daemon  

telnet terminal connection.  

mail delivery.  

TCP port for DNS.  

POP3 port.  

Ident port (always reports none).  

IMAP4rev1 port.  

CIFS/SMB file sharing.  

rlogin terminal connection.  

LP daemon; see lp(8).  

report the address of the incoming call.  

Secure IMAP4rev1 port.  

Secure POP3 port.  

PPTP (point-to-point tunnelling protocol) service.  

At least the following services are available in /bin/service.auth, the usual trustsrvdir.

validate a SecureNet box.  

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 network 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

by convention, TCP device bind point  

SOURCE

/sys/src/cmd/aux/listen*.c
/rc/bin/service*

SEE ALSO

authsrv(6), dial(2)

BUGS

Srvdir, trustsrvdir and namespace must all be absolute path names.