accept
Check if the message with the given id and size should be accepted. This function is responsible for incrementing any counters that are implementation-specific along-side returning the result.
Return
special operation code, telling the packet queue how to handle the messages. Note that DROP_MESSAGE will cause the message to be dropped early on in the decoder, which means the incoming bytes will simply be skipped, rather than sliced and decoded.
Parameters
id
the opcode of the message.
size
the real size of the message, not the -1 & -2 constants.