"Hello Martin, For the time being, we are going to stick with the 0.9.2 version because it works. The protocol we use is the UDP-based external FDM. We form the structure NetFDM as defined in the FlightGear header net_fdm.hxx and then send it to the UDP socket. We had problems in the past with the way this structure is defined. It changes with each new release of FlightGear and there is no backward compatibility (i.e. a newer version of FG will not accept a NetFDM structure in the older format) Also there is the byte alignment problem - depending on compiler settings, the NetFDM structure will have a different size, and if the size comes out to be different than the one FlightGear expects, the data is rejected."
It might help to give FlightGear a well defined, at least compiler- (better: platform-) independent NetFDM interface,
Out of necessity this structure is extended as new needs are discovered. We include a version number in the structure so software on either end can verify they are passing the same version of the contents.
The included source code that can take an instance of NetFDM and translate it into FG properties as well as the code that can build an instance of NetFDM from the current state of the property tree can optionally do it's work in network byte order.
When the structure does change, it is literally trivial to upgrade the other end. Copy over the new structure, see if you care about any of the new fields (usually not) and recompile your software.
If they want the ultimate in flexibility they should use Eric's "generic" output facility because there you can define exactly what output you want via an xml config file and it only changes when you want it to change.
Curt. -- Curtis Olson Intelligent Vehicles Lab FlightGear Project Twin Cities [EMAIL PROTECTED] [EMAIL PROTECTED] Minnesota http://www.menet.umn.edu/~curt http://www.flightgear.org
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