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 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). Option -q suppresses affir- mative log information. Option -i suppresses the periodic 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. At least the following services are available in /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). tcp17007 serve a piece of the name space using the Plan 9 LISTEN(8) LISTEN(8) file system protocol, with authentication at the start, optional SSL encryption, and no multiplex- ing of users (typically used by cpu(1) and import(4)). Not usable by user none. tcp17008 like tcp17007, but serves the root of the tree, forgoing the negotiation for which subtree to serve. tcp17009 rx remote execution. tcp17010 server for cpu(1) command. tcp17013 server for old cpu(1) command for compatibility with old clients. tcp17019 server for rcpu(1), replaces rx, import(4) and cpu(1) 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 LISTEN(8) LISTEN(8) 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.