OPC UA PubSub Traps And Pitfalls

Error "Unable to activate the adapter (...). Return code: -8"

On Linux, elevated privileges are needed in order to send raw Ethernet packets. Run your program with sudo to resolve this issue.

Error "Unable to load shared library 'libpcap' or one of its dependencies. ..."

If you are on Ubuntu 18: Libpcap is "preinstalled", but SharpPcap won't find it. There are various ways how to resolve it. One of them is to create a copy of symlink /user/lib/x86_64-linux-gnu/libpcap.so.0.8 to symlink libpcap.so in the same directory.

Subscriber does not receive anything, even when no filter is specified - but I am sure the publisher works.

Check that you are publishing and subscribing on the intended network interfaces. On computers with multiple interfaces, which is now common, a default interface is chosen by the software when no interface is specified, and it may commonly be a wrong choice. In tools like OpcCmd or UADemoSubscriber, use the -ConnectionNetworkInterface (-cni) option. In subscriber code, set the InterfaceName property of UAPubSubConnectionDescriptor.ResourceAddress.

Subscriber does not receive anything, when on the same host as the publisher.

This happens with some network adapters. You can install and use a loopback adapter to make it work. On Windows 10, run Add Hardware Wizard (hdwwiz.exe), tell it that you want to select the hardware manually from a list, and from Network Adapters, select Microsoft -> Microsoft KM-TEST Loopback Adapter.