In many cases, all code needed to perform OPC UA PubSub functionality is contained directly in core OPC Data Client assemblies. There are some situations, however, when one or more additional pieces of software ("package") is needed.

For more information about the use of communication packages in general, see http://kb.opclabs.com/Using_communication_packages .

OpcLabs.Pcap communication package

OpcLabs.Pcap is an external assembly/package of OPC Data Client that is only needed for: 

• OPC UA PubSub Ethernet transport (the "opc.eth" scheme).
• OPC UA PubSub reading or writing Wireshark capture files.

OPC Data Client switches to the OpcLabs.Pcap communication package whenever it detects that any of the above is required. Although OpcLabs.Pcap use does not require anything different from the coding point of view, it requires special handling in several respects - e.g. with regard to licensing, installation, and configuration.

For more information about OpcLabs.Pcap, see http://kb.opclabs.com/OpcLabs.Pcap_communication_package .

MQTT communication packages

MQTT communication is not built-into core OPC Data Client assemblies, but is rather always provided externally, by means of a package that uses some specific MQTT communication library. OPC Data Client automatically uses a default MQTT communication package unless you make a different choice. In case you are fine with the default MQTT communication package selection, you do not need to do anything special in your code, but you still need to make sure that the package is installed and referenced, and you may also want to configure it in some specific way.

For more information about the packages available, see http://kb.opclabs.com/MQTT_communication_packages .

Besides packages that provide "true" MQTT communication, a File-based MQTT emulation, useful for experiments and troubleshooting, is also available.