listen(5)

                                  listen(1M)
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   listen -- network listener port monitor 

Synopsis

   /usr/lib/saf/listen [-m devstem] net_spec

Description

   The listen port monitor ``listens'' to a network for service requests,
   accepts requests when they arrive, and invokes servers in response to
   those service requests.

Files

   /etc/saf/pmtag/ *
          service support files grouped according to port monitor tag (as
          listed by sacadm -l)

Usage

   The network listener process may be used with any connection-oriented
   network (more precisely, with any connection-oriented transport
   provider) that conforms to the Transport Interface (TLI)
   specification.

   The listener internally generates a pathname for the minor device for
   each connection; it is this pathname that is used in the utmp entry
   for a service, if one is created. By default, this pathname is the
   concatenation of the prefix /dev/netspec with the decimal
   representation of the minor device number. When the -m devstem option
   is specified, the listener will use devstem as the prefix for the
   pathname. In either case, the representation of the minor device
   number will be at least two digits (for example, 05 or 27), but will
   be longer when necessary to accommodate minor device numbers larger
   than 99.

  Server invocation

   When a connection indication is received, the listener creates a new
   transport endpoint and accepts the connection on that endpoint. Before
   giving the file descriptor for this new connection to the server, any
   designated STREAMS modules are pushed and the configuration script is
   executed, if one exists. This file descriptor is appropriate for use
   with either TLI (see especially t_sync(3xti)) or the sockets interface
   library.

   By default, a new instance of the server is invoked for each
   connection. When the server is invoked, file descriptor 0 refers to
   the transport endpoint, and is open for reading and writing. File
   descriptors 1 and 2 are copies of file descriptor 0; no other file
   descriptors are open. The service is invoked either with the user ID
   under which the service was registered with the listener, or as an
   authenticated ID if an authentication scheme was specified instead. If
   both an ID and authentication scheme are specified for the service in
   the listener's administrative file, the listener does the
   authentication, but then runs the service under the specified ID.

   Alternatively, a service may be registered so that the listener will
   pass connections to a standing server process through a FIFO or a
   named stream, instead of invoking the server anew for each connection.
   In this case, the connection is passed in the form of a file
   descriptor that refers to the new transport endpoint. Before the file
   descriptor is sent to the server, the listener interprets any
   configuration script registered for that service using doconfig(3iac),
   although doconfig is invoked with both the NORUN and NOASSIGN flags.
   The server receives the file descriptor for the connection in a
   strrecvfd structure via an I_RECVFD ioctl(2).

   For more details about the listener and its administration, see
   nlsadmin(1M).

Warnings

   When passing a connection to a standing server, the user and group IDs
   contained in the strrecvfd structure will be those for the listener;
   the user name under which the service was registered with the listener
   or the authenticated ID is not reflected in these IDs.

   When operating multiple instances of the listener on a single
   transport provider, there is a potential race condition in the binding
   of addresses during initialization of the listeners if any of their
   services have dynamically assigned addresses. This condition would
   appear as an inability of the listener to bind a static-address
   service to its otherwise valid address, and would result from a
   dynamic-address service having been bound to that address by a
   different instance of the listener.

References

   doconfig(3iac), nlsadmin(1M), nlsgetcall(3N), nlsprovider(3N),
   pmadm(1M), sac(1M), sacadm(1M), streamio(7)
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   © 2004 The SCO Group, Inc. All rights reserved.
   UnixWare 7 Release 7.1.4 - 25 April 2004
   
See also listen(3sock)