problems with Distributed Objects and PyObjC

[Hamish Sanderson]

Hi all,

Trying to use Distributed Objects to communicate between PyObjC-based  
processes on 10.5 and/or 10.6, but encountering various problems when  
passing Python values, as illustrated below. The production code  
currently only passes Python strings as arguments so I can work around  
these issues for now by ensuring I always wrap them as NSStrings, but  
it's going to create headaches if I start to use DO for more advanced  
IPC.

Anyone any thoughts? (Including suggestions for alternative LAN-
capable IPC options.)

Thanks,

Hamish


------- doserver.py -------

from Cocoa import *

class Server(NSObject):
        def test(self, arg):
                print 'received:', arg
                return NSString.stringWithString_(u"ok")

receiveport = NSSocketPort.alloc().initWithTCPPort_(8080)
connection =  
NSConnection.connectionWithReceivePort_sendPort_(receiveport, None)
server = Server.alloc().init()
connection.setRootObject_(server)
NSRunLoop.mainRunLoop().run()



------- doclient.py -------

from Cocoa import *

sendport = NSSocketPort.alloc().initRemoteWithTCPPort_host_(8080,  
u"localhost")
connection = NSConnection.connectionWithReceivePort_sendPort_(None,  
sendport)
proxy = connection.rootProxy()

try:
        print "reply", proxy.test(43)
except Exception, e:
        print e
# doclient.py fails:
# ValueError: NSInvalidArgumentException - *** -encodeInt:forKey: only  
defined for abstract class.
#    Define -[NSConcretePortCoder encodeInt:forKey:]!

print "reply", proxy.test(NSNumber.numberWithInt_(43)) # OK

try:
        print "reply", proxy.test([]) # OK on 10.6
except Exception, e:
        print e
# doclient.py fails on 10.5
# ValueError: NSInvalidArgumentException - PyObjC: Encoding python  
objects of type list is not supported

print "reply", proxy.test(True) # OK

print "reply", proxy.test(NSString.stringWithString_(u'hello')) # OK

print "reply", proxy.test(u'hello') # OK on 10.5
# doserver.py fails on 10.6:
# ValueError: NSInvalidArgumentException - -[OC_PythonUnicode  
initWithBytes:length:encoding:]:
#    unrecognized selector sent to instance 0x100261a80



--

Hamish Sanderson
Production Workflow Developer
Sun Branding Solutions Ltd
Tel: [phone]
www.s-brandingsolutions.com




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[Ronald Oussoren]

 
On Tuesday, October 20, 2009, at 01:20PM, "Hamish Sanderson" <hsanderson@...> wrote:

>Hi all,
>
>Trying to use Distributed Objects to communicate between PyObjC-based  
>processes on 10.5 and/or 10.6, but encountering various problems when  
>passing Python values, as illustrated below. The production code  
>currently only passes Python strings as arguments so I can work around  
>these issues for now by ensuring I always wrap them as NSStrings, but  
>it's going to create headaches if I start to use DO for more advanced  
>IPC.
>
>Anyone any thoughts? (Including suggestions for alternative LAN-
>capable IPC options.)

Full DO support requires defining new protocols, which won't work on 64-bit builds.  Even the limited DO support you need may or may not work because it is a low-level library that might interfere with PyObjC. I don't have unittests or sample code for this and hence cannot guarantee that this will work.  

I will look into your issues though, but not today.

An alternative to DO is to use a native Python library (Twisted, XML-RPC, ...) combined with Bonjour.

Ronald

>
>Thanks,
>
>Hamish
>
>
>------- doserver.py -------
>
>from Cocoa import *
>
>class Server(NSObject):
> def test(self, arg):
> print 'received:', arg
> return NSString.stringWithString_(u"ok")
>
>receiveport = NSSocketPort.alloc().initWithTCPPort_(8080)
>connection =  
>NSConnection.connectionWithReceivePort_sendPort_(receiveport, None)
>server = Server.alloc().init()
>connection.setRootObject_(server)
>NSRunLoop.mainRunLoop().run()
>
>
>
>------- doclient.py -------
>
>from Cocoa import *
>
>sendport = NSSocketPort.alloc().initRemoteWithTCPPort_host_(8080,  
>u"localhost")
>connection = NSConnection.connectionWithReceivePort_sendPort_(None,  
>sendport)
>proxy = connection.rootProxy()
>
>try:
> print "reply", proxy.test(43)
>except Exception, e:
> print e
># doclient.py fails:
># ValueError: NSInvalidArgumentException - *** -encodeInt:forKey: only  
>defined for abstract class.
>#    Define -[NSConcretePortCoder encodeInt:forKey:]!
>
>print "reply", proxy.test(NSNumber.numberWithInt_(43)) # OK
>
>try:
> print "reply", proxy.test([]) # OK on 10.6
>except Exception, e:
> print e
># doclient.py fails on 10.5
># ValueError: NSInvalidArgumentException - PyObjC: Encoding python  
>objects of type list is not supported
>
>print "reply", proxy.test(True) # OK
>
>print "reply", proxy.test(NSString.stringWithString_(u'hello')) # OK
>
>print "reply", proxy.test(u'hello') # OK on 10.5
># doserver.py fails on 10.6:
># ValueError: NSInvalidArgumentException - -[OC_PythonUnicode  
>initWithBytes:length:encoding:]:
>#    unrecognized selector sent to instance 0x100261a80
>
>
>
>--
>
>Hamish Sanderson
>Production Workflow Developer
>Sun Branding Solutions Ltd
>Tel: [phone]
>www.s-brandingsolutions.com
>
>
>
>
>_______________________________________________
>Pythonmac-SIG maillist  -  Pythonmac-SIG@...
>http://mail.python.org/mailman/listinfo/pythonmac-sig
>
>

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[Irmen de Jong-2]

Hamish Sanderson wrote:

> Hi all,
>
> Trying to use Distributed Objects to communicate between PyObjC-based
> processes on 10.5 and/or 10.6, but encountering various problems when
> passing Python values, as illustrated below. The production code
> currently only passes Python strings as arguments so I can work around
> these issues for now by ensuring I always wrap them as NSStrings, but
> it's going to create headaches if I start to use DO for more advanced IPC.
>
> Anyone any thoughts? (Including suggestions for alternative LAN-capable
> IPC options.)

Both ends are Python?
If they are, maybe you should try Pyro (http://pyro.sourceforge.net).

--irmen
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