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Adrian Georgescu, 03/12/2009 07:50 pm

= MSRP API =

<acronym title="WikiStart, Sip*, depth=3">TOC</acronym>

Message Session Relay Protocol (MSRP) is a protocol for transmitting a series of related instant messages in the context of a session. Message sessions are treated like any other media stream when set up via a rendezvous or session creation protocol such as the Session Initiation Protocol (SIP).

The MSRP protocol is implemented by [http://devel.ag-projects.com/cgi-bin/darcsweb.cgi?r=python-msrplib;a=summary msrplib] Python package.

Architecture

{{{msrplib}}} is based upon [http://twistedmatrix.com twisted] and [http://devel.ag-projects.com/~denis/eventlet/ eventlet] and provides a set of
classes for establishing and managing MSRP connection.

The library consist of the following modules:

'''msrplib.transport'''::
 Defines {{{MSRPTransport}}} class, which provides low level control over MSRP connection.
'''msrplib.connect'''::
 Defines means to establish a connection, bind it, and provide a usable {{{MSRPTransport}}} instance.
'''msrplib.session'''::
 Defines {{{MSRPSession}}} class, which provides high level control over a MSRP connection.
'''msrplib.protocol'''::
 Provides representation and parsing of MSRP entities - chunks and URIs.
'''msrplib.trafficlog'''::
 Defines {{{Logger}}} class that is used through out the library to log the connection state.
Usage

{{{msrplib.connect}}} provides a number of classes to establish a connection, so the first
thing to do is to select which one applies to your situation:

1. Calling endpoint, not using a relay ({{{ConnectorDirect}}})
    2. Answering endpoint, not using a relay ({{{AcceptorDirect}}})
    3. Calling endpoint, using a relay ({{{ConnectorRelay}}})
    4. Answering endpoint, using a relay ({{{AcceptorRelay}}})

The answering endpoint may skip using the relay if sure that it's accessible
directly. The calling endpoint is unlikely to need the relay.

Once you have an instance of the right class (use the convenience functions {{{get_connector()}}} and {{{get_acceptor()}}} to get one), the procedure to establish the
connection is the same:

{{{
full_local_path = connector.prepare()
try:
... put full_local_path in SDP 'a:path' attribute
... get full_remote_path from remote's 'a:path: attribute
... (the order of the above steps is reversed if you're the
... answering party, but that does not affect connector's usage)
msrptransport = connector.complete(full_remote_path)
finally:
connector.cleanup()
}}}

To customize connection's parameters, create a new {{{protocol.URI}}} object and pass
it to prepare() function, e.g. {{{
local_uri = protocol.URI
connector.prepare(local_uri)
}}}

{{{prepare()}}} may update {{{local_uri}}} in place with the actual connection parameters
used (e.g. if you specified port=0). 'port' attribute of {{{local_uri}}} is currently
only respected by {{{AcceptorDirect}}}.

Note that, acceptors and connectors are one-use only. Which means, that {{{AcceptorDirect}}}
will open a port just to handle one incoming connection and close it right after.
If your application behaves more like a server, i.e. opens a port and listens on it
constantly, use {{{MSRPServer}}} class.

Components

=== a connector or acceptor ===

==== attributes ==== ==== methods ====

=== transport.MSRPTransport === ==== attributes ==== ==== methods ====

=== session.MSRPSession === ==== attributes ==== ==== methods ====

=== connect.MSRPServer === ==== attributes ==== ==== methods ====