Add OPC-UA server/client for OPC-UA network throughput test
This adds an OPC-UA server and an OPC-UA client. The client performs tests that measure the throughput between an OPC-UA server and client. See ./server.py --help and ./client.py --help for details. For convenience and a quick check execute ./start_server.sh and ./start_client.sh on your machine. The Python code uses two libraries that should be installed in a Python3 venv:
cd python3 -m venv env
source env/bin/activate
python3 -m pip install --upgrade pip wheel
python3 -m pip install -r requiremetns.txt