Hi, I finished building a small layer in freevo for easy mbus access. It's in cvs now and you can test it by using the mbusctl helper to start or stop playback in Freevo. You need the latest version of pyNotifier and pyMbus, they were released today on www.mbus.org. You can also simply call 'make' in Freevo to download the files and let them install themself to ./lib.
Here two small howtos from the Docs dir. The first is the
configuration howto, the second the programming howto. Please test and
let me know what you think. Also give feedback on the interface.
[ Installation doc ]
This document describes how to setup mbus.
1. Configuration file
All known mbus implementations read the config file ~/.mbus or if
the environment variable MBUS set, the file to which this variable
points. When you first start freevo or a helper application a mbus
configuration file is created. Please check the variables later. If
you have mbus applications on different hosts, you need to change
SCOPE=HOSTLOCAL to SCOPE=LINKLOCAL.
All applications on the same bus must share most of the values in
the config file. If ADDRESS or PORT don't match, the applications
simply won't find each other, if HASHKEY is different, pymbus won't
deliver the messages. Do not activate ENCRYPTIONKEY, pyMbus doesn't
support encryption yet.
2. Multicast setup
Mbus communicates over multicast. Most Linux distributions enable
multicast in their default kernel. If you build your own kernel,
make sure multicast is enabled.
If no special route is given, the multicast traffic will be routed
through the default route. This may not what you want. E.g. eth0 is
the uplink and eth1 the private network, eth0 has the default route
but eth1 should be used for link local mbus communication. A second
problem may be that the firewall is blocking the communication and
not even host local communication is possible.
To set the default route for mbus for 224.255.222.240 (default)
type 'route add 224.255.222.240 <interface>' is root. For host
local usage use 'lo' as <interface>.
[ Coding howto ]
This document describes how to use the freevo mbus layer.
Freevo has a wrapper for the important mbus functions for easier
access inside helpers and plugins. By using the wrapper, the
application will join the mbus with the following naming scheme:
"app=freevo, type=home-theatre, module=name" with name being the name
of the helper or 'core' for the main freevo application.
You can also create more than one entity inside an application, a
howto for this will follow later.
First let's make an example how to use client server communication
over mbus. That's the only thing working right now in the wrapper,
events will come later. PyMbus supports much more than the mcomm
layer, so maybe it is necessary to import mbus in a plugin for special
stuff.
Creating a server:
To create a server you must inherit from mcomm.RPCServer. It is
possible to have more than one server on one bus, the class is only a
wrapper for easy access. Each function starting with __rpc_ and ending
with __ will be registered as rpc to the mbus entity. So let's say you
have a plugin listening to the rpc home.theatre.play, you would create
the following plugin:
| class PluginInterface(plugin.Plugin, mcomm.RPCServer):
| def __init__(self):
| plugin.Plugin.__init__(self)
| mcomm.RPCServer.__init__(self)
|
| def __rpc_play__(self, addr, val):
| file = self.parse_parameter(val, ( str, ))
|
| if not eventhandler.is_menu():
| return mcomm.RPCError('freevo not in menu mode')
|
| menuw = eventhandler.get()
| parent = menuw.menustack[-1].selected
|
| for p in plugin.mimetype(None):
| i = p.get(parent, [ file ] )
| if i and hasattr(i[0], 'play'):
| i[0].play(menuw=menuw)
| return mcomm.RPCReturn([])
|
| return mcomm.RPCError('no player found')
Simple, isn't it? Now, how does the client look like?
| freevo = mcomm.find('freevo')
|
| if not freevo:
| print 'freevo not running'
| sys.exit(0)
|
| try:
| freevo.play('/my/file.mp3')
| except mcomm.MException, e:
| print e
That's all. mcomm.find will wait on the bus until the freevo core
comes up (timeout 10 sec). Calling freevo.play will result in a mbus
call home-theatre.play with the given argument. There are three
possible returns:
1. (True, return values)
The server sent mcomm.RPCReturn(return values). Everything worked
as expected.
2. (False, reason)
The server send mcomm.RPCError(reason). The parameter are ok, but
it was not possible to do what expected.
3. mcomm.MException is raised. Something went wrong. Possible reasons
are a crash on server side, a server not answering and so on.
freevo.play will block until the result is there. If you don't want to
wait, you can specify a callback to the function:
freevo.play('/my/file.mp3', callback=my_function)
This callback will get the raw mbus return, no True, False or
MException stuff.
Dischi
--
The Second Law of Thermodynamics:
If you think things are in a mess now, just wait!
-- Jim Warner
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