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### Cancel a sessionless signal in java

I have a sessionless signal with no TTL that I would like to cancel. I'm using the java binding and I've seen there is a cancelSessionlessSignal method on the SignalEmitter object, but it requires a serialNum argument to identify the signal to be cancelled, and I don't see how to get this id in java.

Is there anyway, with the java binding, to get the signal serial number ?