There are no documentation but you can inspect the actual protocol by running fop2_server in debug mode level 12...
service fop2 stop
cd /usr/local/fop2
script capture.log
./fop2_server -X 12
(connect, make calls to receive events, perform some action)
ctrl-c
exit
service fop2 start
Then you will have a nice log file with all the transactions between client/server.
Best regards,
