Types are not supported

[NicolasLagaillardie]

ADD(Int) → Recv<N, End>;
BYE() → Recv<(), End>

[NicolasLagaillardie]

Change

	private String getPayload(EAction a) {
		return "N";
	}

to something to return the type given in

Adder(Int)

or

Bye()

[NicolasLagaillardie]

To make it simple: in case of nothing, return "()", else, return "N".