Re: PDO replacement attempts, or How to setReturnValue of an NSInvocation

[Richard Frith-Macdonald]

On Sunday, January 6, 2002, at 08:58 AM, OSX Developer wrote:

> Hello I have been trying to replace the no longer properly supported 
> PDO Portable Distributed Objects System in OSX Server 10.1.2.
> I thought someone here might be able to help or explain if this works 
> in GnuStep, which might help me to understand the bugs in OSX or if 
> there really is a way to do it in gnustep somehow maybe (I am not sure).
>
> I have a summary and detailed description of my attempts and problems 
> which I will appemt that was intended for another newsgroup for osx 
> developers at omniweb. [So Sorry if this is the wrong place but there 
> are few options available to try otherwise.]
>
> Basically I have my own Connection DistantObject, with a tri-set of 
> tools; a hub-server, a server, and client tool. All integrated to 
> replace PDO.
>
> I was able to send an NSInvocation via a socket as a data stream after 
> Archiving and Unarchiving the Invocation (via NSArchiver and 
> NSUnarchiver).
> The real problems come when returning the post-invoked NSInvocation or 
> just simply trying to set the return value, setReturnValue:.

I can't really help with NeXT/Apples PDO stuff ... the internals of that 
almost certainly don't operate in
quite the same way as those of GNUstep Distributed Objects.  In general, 
you can't have a GNUstep application
talk directly to a MacOS-X application using distributed objects, as 
both the protocol and the internal coding
of objects used by MacOS-X are proprietory and undocumented.

If you port to use the GNUstep base library, the GNUstep distributed 
object system should work between
different machines and architectures so you don't need to write your own 
DO system (quite a big task).
And of course, if you have problems (eg porting to new hardware 
architectures) you can see the source,
fix the problems, and contribute the fixes back.

One hint though ... generally, for DO you use an NSPortCoder to perform 
the serialisation of objects for
transmission between processes/machines.  The NSArchiver/NSUnarchiver 
combination is not really designed
for quite the same job so it's not too surprising if it doesn't quite 
work :-)