udpsvd(8)						      System Manager's Manual							 udpsvd(8)

NAME

       udpsvd - UDP/IP service daemon

SYNOPSIS

       udpsvd [-hpvv] [-u user] [-l name] [-i dir|-x cdb] [-t sec] host port prog

DESCRIPTION

       udpsvd creates an UDP/IP socket, binds it to the address host:port, and listens on the socket for incoming datagrams.

       If  a datagram is available on the socket, udpsvd conditionally starts a program, with standard input reading from the socket, and standard
       output redirected to standard error, to handle this, and possibly more datagrams.  udpsvd does not start the  program  if  another  program
       that  it  has started before still is running.  If the program exits, udpsvd again listens to the socket until a new datagram is available.
       If there are still datagrams available on the socket, the program is restarted immediately.

       udpsvd optionally checks for special intructions depending on the IP address or hostname of the client sending the datagram which  not  yet
       was handled by a running program, see ipsvd-instruct(5) for details.

   ATTENTION:
       UDP is a connectionless protocol.  Most programs that handle user datagrams, such as talkd(8), keep running after receiving a datagram, and
       process subsequent datagrams sent to the socket until a timeout is reached.  udpsvd only checks special instructions for  a  datagram  that
       causes  a  startup  of  the program; not if a program handling datagrams already is running.  It doesn't make much sense to restrict access
       through special instructions when using such a program.

       On the other hand, it makes perfectly sense with programs like tftpd(8), that fork to establish a separate connection to  the  client  when
       receiving the datagram.	In general it's adequate to set up special instructions for programs that support being run by tcpwrapper.

OPTIONS

       host   host either is a hostname, or a dotted-decimal IP address, or 0.	If host is 0, udpsvd accepts datagrams to any local IP address.

       port   udpsvd accepts datagrams to host:port.  port may be a name from /etc/services or a number.

       prog   prog  consists  of  one  or  more arguments.  udpsvd normally runs prog to handle a datagram, and possibly more, that is sent to the
	      socket, if there is no program that was started before by udpsvd still running and handling datagrams.

       -i dir read instructions for handling new connections from the instructions directory dir.  See ipsvd-instruct(5) for details.

       -x cdb read instructions for handling new connections from the constant database cdb.  The constant database normally is  created  from	an
	      instructions directory by running ipsvd-cdb(8).

       -t sec timeout.	 This  option  only  takes effect if the -i option is given.  While checking the instructions directory, check the time of
	      last access of the file that matches the clients address or hostname if any, discard and remove  the  file  if  it  wasn't  accessed
	      within the last sec seconds; udpsvd does not discard or remove a file if the user's write permission is not set, for those files the
	      timeout is disabled.  Default is 0, which means that the timeout is disabled.

       -l name
	      local hostname.  Do not look up the local hostname in DNS, but use name as hostname.  By default udpsvd looks up the local  hostname
	      once at startup.

       -u [:]user[:group]
	      drop  permissions.  Set uid and gid to the user's uid and gid, as found in /etc/passwd, before running prog.  If user is followed by
	      a colon and a group, set the gid to group's gid, as found in /etc/group, instead of user's gid.  If group consists of a  colon-sepa-
	      rated  list  of group names, set the group ids of all listed groups.  If user is prefixed with a colon, the user and all group argu-
	      ments are interpreted as uid and gids respectively, and not looked up in the password or group file.  All supplementary  groups  are
	      removed.

       -h     Look up the client's hostname in DNS.

       -p     paranoid.  After looking up the client's hostname in DNS, look up the IP addresses in DNS for that hostname, and forget the hostname
	      if none of the addresses match the client's IP address.  You should set this option if you use hostname based instructions.  The	-p
	      option implies the -h option.

       -v     verbose.	Print verbose messages to standard output.

       -vv    more verbose.  Print more verbose messages to standard output.

SEE ALSO

       ipsvd(7), tcpsvd(8), sslsvd(8), ipsvd-instruct(5), ipsvd-cdb(8)

       http://smarden.org/ipsvd/

AUTHOR

       Gerrit Pape <pape@smarden.org>

																	 udpsvd(8)