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NAME

       nameserv::protocol - Name service facility, client/server protocol

SYNOPSIS

       Bind name data

       Release

       Search pattern

       ProtocolVersion

       ProtocolFeatures

       Search/Continuous/Start tag pattern

       Search/Continuous/Stop tag

       Search/Continuous/Change tag add|remove response

_________________________________________________________________

DESCRIPTION

       The packages nameserv::server, nameserv, and nameserv::common provide a simple unprotected
       name service facility for use in small trusted environments.

       Please read Name service facility, introduction first.

       This document contains the specification of the network protocol which is used  by  client
       and  server  to talk to each other, enabling implementations of the same protocol in other
       languages.

NANO NAME SERVICE PROTOCOL VERSION 1

       This protocol defines the basic set of messages to be supported by a  name  service,  also
       called the Core feature.

   BASIC LAYER
       The  basic  communication  between  client  and  server is done using the remote-execution
       protocol specified by the Tcl package comm.  The relevant document specifying its  on-the-
       wire protocol can be found in comm_wire.

       All  the scripts exchanged via this protocol are single commands in list form and thus can
       be interpreted as plain  messages  instead  of  as  Tcl  commands.  The  commands/messages
       specified in the next section are the only commands understood by the server-side. Command
       and variable substitutions are not allowed within the messages, i.e. arguments have to  be
       literal values.

       The protocol is synchronous. I.e. for each message sent a response is expected, and has to
       be generated. All messages are sent by the client.  The server  does  not  sent  messages,
       only responses to messages.

   MESSAGE LAYER
       Bind name data
              The  client  sends this message when it registers itself at the service with a name
              and some associated data. The server has to send an error response if the  name  is
              already in use. Otherwise the response has to be an empty string.

              The server has to accept multiple names for the same client.

       Release
              The  client  sends  this  message  to unregister all names it is known under at the
              service. The response has to be an empty string, always.

       Search pattern
              The client sends this message to search the service for names  matching  the  glob-
              pattern. The response has to be a dictionary containing the matching names as keys,
              and mapping them to the data associated with it at Bind-time.

       ProtocolVersion
              The client sends this message to query the service for the highest version  of  the
              name  service  protocol  it  supports.  The  response  has to be a positive integer
              number.

              Servers supporting only Nano Name Service Protocol Version 1 have to return 1.

       ProtocolFeatures
              The client sends this message to query the service for the  features  of  the  name
              service  protocol  it  supports.  The  response has to be a list containing feature
              names.

              Servers supporting only Nano Name Service Protocol Version 1 have to return {Core}.

NANO NAME SERVICE PROTOCOL EXTENSION: CONTINUOUS SEARCH

       This protocol defines an extended set of messages to be supported by a name service,  also
       called  the  Search/Continuous  feature.  This feature defines additional messages between
       client and server, and is otherwise identical to version 1 of the protocol. See  the  last
       section for the details of our foundation.

       A  service  supporting this feature has to put the feature name Search/Continuous into the
       list of features returned by the message ProtocolFeatures.

       For this extension the protocol is asynchronous. No direct response is expected for any of
       the  messages  in the extension. Furthermore the server will start sending messages on its
       own, instead of only responses to messages, and the client has to be able to handle  these
       notifications.

       Search/Continuous/Start tag pattern
              The client sends this message to start searching the service for names matching the
              glob-pattern.  In contrast to the regular Search request this one asks  the  server
              to  continuously  monitor  the  database  for  the addition and removal of matching
              entries and to notify the client of all such  changes.  The  particular  search  is
              identified by the tag.

              No direct response is expected, rather the clients expect to be notified of changes
              via explicit Search/Continuous/Result messages generated by the service.

              It is further expected  that  the  tag  information  is  passed  unchanged  to  the
              Search/Continuous/Result  messages.  This tagging of the results enables clients to
              start multiple searches and distinguish between the different results.

       Search/Continuous/Stop tag
              The client sends this message to stop the continuous search identified by the tag.

       Search/Continuous/Change tag add|remove response
              This message is sent by the service to clients with active continuous  searches  to
              transfer  found  changes. The first such message for a new continuous search has to
              contains the current set of matching entries.

              To ensure this a service has to generate an add-message with an empty  response  if
              there were no matching entries at the time.

              The  response  has  to  be  a dictionary containing the matching names as keys, and
              mapping them to the data associated with it  at  Bind-time.   The  argument  coming
              before  the  response tells the client whether the names in the response were added
              or removed from the service.

BUGS, IDEAS, FEEDBACK

       This document, and the package it describes,  will  undoubtedly  contain  bugs  and  other
       problems.   Please  report  such  in  the  category  nameserv  of  the  Tcllib SF Trackers
       [http://sourceforge.net/tracker/?group_id=12883].   Please  also  report  any  ideas   for
       enhancements you may have for either package and/or documentation.

SEE ALSO

       comm_wire(3tcl), nameserv(3tcl), nameserv::server(3tcl)

KEYWORDS

       comm, name service, protocol

CATEGORY

       Networking

COPYRIGHT

       Copyright (c) 2007-2008 Andreas Kupries <andreas_kupries@users.sourceforge.net>