Description of the new interface protocol (version 2.00)
  ========================================================

The protocol is mainly specified by its implementation in files

common/commonTypes.ml (generic types)
commmon/gui_proto.ml (GUI protocol)

The specification should be moved in an human readable form to this file in
the future.

Basic ideas:
============

  The GUI must connect to the core via a TCP socket. Binary messages are
sent on this socket, with the following format:

| size of content (4 bytes) | content |

size of content: 4 bytes integer (in network order, ie
  1025 = 1 + 256 * 4 = |   1 |   4 |  0 |  0 | ), indicating the length
  of the content of the message

content: the content of the message. the content starts by a 2 bytes integer,
  which is the opcode of the message, followed with the arguments.
  If the opcode is not known by the GUI, the GUI can simply discard the whole
  message, and continue with other messages (this way, partial implementations
  of the protocol should work for simple functions).

  | opcode (2 bytes) | arguments |

When connected, both sides start by sending a 0-opcode message, with
a 4-bytes argument indicating the version of the protocol used 
(CoreProtocol and GuiProtocol messages in the gui_proto.ml file).

Then, they should use the smallest protocol version, so that all messages 
should be understandandable by both sides (the core should always remain
backward compatible in the future with old versions of this GUI protocol).

Current version of the protocol is 0.

The remaining of this file will describe encoding and meaning of messages.
Some remarks:

 - In the core, all data structures have unique identifiers (an integer)
   in their types (one result and one server can have the same number, but
   not two different results). Thus, these identifiers are often used
   between the GUI and the core.

 - The basic core engine uses the following types:

      network: a peer to peer network (donkey, open napster, gnutella, ...)
      search: a search (network independant)

      server: a server on a given network
      file: a file being downloaded on a given network
      client: a source for a file being downloaded, or a friend
      result: the result of a search, or a browse operation on a friend
      user: another peer connected on a server, or a source for a result of 
             a search (it will become a client if we download its files or
             if it becomes a friend)
      room: a chat room, with many users connected to dialog.

Basic encoding:
===============

  For basic types, the following encoding is used in the messages:

int8: one byte
int16: two bytes in network order
int/int32: 4 bytes in network order
                      1025 = 1 + 256 * 4  =     |   1 |   4 |  0 |  0 | 

string: an int16 for the length, followed by the characters of the string
  without 0 at the end.

bool: an int8, with 0 for FALSE and 1 for TRUE.

float: a string (see above), ASCII representation of the float.

list or arrays of values: an int16 for the number of elements, followed by
   the elements, without separators. 

records, pairs, tuples: the fields are encoded without separators.

md4: the 16 bytes corresponding to the hash.

Messages from Core to GUI for protocol 0
========================================
CoreProtocol (opcode 0) + int32 (protocol version)

    Indicates the most up-to-date version of the protocol understood by the 
    core.

Options_info (opcode 1) + a list of string pairs

    Indicates the names of some options and their associated value (converted
    to a string).

DefineSearches (opcode 3) + query description list

    Indicates to the GUI predefined or user-defined queries formats.
    See buf_query in gui_proto.ml to see how queries are encoded exactly.

Result_info (opcode 4) + result description

    Describes a result. The result is not associated with a search.
    Another message is used to associate the result (number) with a search.

    result format: see buf_result in gui_proto.ml.

etc...

Messages from GUI to Core for protocol 0
========================================