The protocol modules are suffering somewhat from a lack of diagnostic tools at the moment. Specifically ways to pretty-print PDUs that aren't recognized by the system. We'll include something to this end in a not-too-distant release. In the meantime, what we do when we get packages we don't understand is to compile the ODR module with ODR_DEBUG defined. This causes the module to dump tracing information as it processes data units. With this output and the protocol specification (Z39.50), it is generally fairly easy to see what goes wrong.