The PublisherId is a unique identifier for a Publisher within a Message Oriented Middleware. It can be included in sent NetworkMessage for identification or filtering. The value of the PublisherId is typically shared between PubSubConnections but the assignment of the PublisherId is vendor specific.
The default PublisherId for datagram transport protocols has a DataType of UInt64. If the default PublisherId is created by the OPC UA Application, it is recommended to set the first 6 bytes with the MAC address of one of the network interfaces and to set the two remaining bytes to the OPC UA Server port of the OPC UA Application.
The default PublisherId for broker based transports equals the PublisherId for datagram transport protocols but the DataType is UInt64 for UADP message mapping and String for JSON message mapping. For the String, the UInt64 value is converted to a String. The PublisherId may be used in message headers, as part of a QueueName or as a client identifier for the broker connection. In these cases the size of the PublisherId and the characters used in the PublisherId may have limitations or impact to the communication performance.
The default PublisherId is used if it is not assigned by a configuration tool.