 to a first of a series of at least one service interface between two layers in a protocol stack, each service interface configured to remove at least one packet header from the packet and process the remainder of the packet using information encoded in the removed packet header, including a service interface configured to assemble the messages for the decoder application from the payload of at least one packet, using information included in at least one header of the packet. The invention also relates to a computer program loadable into a computer and having the potential, when run on the computer, to 