A message handler (61, 62) is described. The message handler is configured, in response to receiving a data package (131, 132) which is formatted according to a given communications protocol, such as CAN or Ethernet, and which comprises package-directing data (22; FIG. 4) and payload data (23; FIG. 4), to generate package (14) having a predetermined data format, for example a layer-2 or layer-3 package, which comprises a header (24; FIG. 4) and payload data (25; FIG. 4). The header comprises an address generated in dependence upon the package-directing data and wherein the payload comprises the data package. The package (14) having a predetermined data format may be an IEEE 1722 frame.