change security policy in milo opc example server - opc

Question

How to change security policy in milo example server? I've tried to connect to milo's opc server with UaExpert, and set the security policy. No matter what security policy I choose, the result is the same error:
ERROR o.e.m.o.s.s.t.u.UascServerAsymmetricHandler - [remote=/127.0.0.1:33762] Exception caught; sent ErrorMessage{error=StatusCode{name=Bad_SecurityChecksFailed, value=0x80130000, quality=bad}, reason=certificate path validation failed}
io.netty.handler.codec.DecoderException: UaException: status=Bad_SecurityChecksFailed, message=certificate path validation failed
How can I configure it correctly?
Second question: The example server seems quite complicated. What is the simplest way to create a server and connect to it? Is there a minimal example for that?

Answer 1

Welcome to stackoverflow
I do not know the Milo server and I have not almost used UAExpert but:
The client must trust the server certificate and the server must do the same with the client's certificate and of course both sides must have their certificate, sometimes the client and the server automatically create one if it doesn't exist but sometimes it should be created previously by external ways.
Help about UAExpert http://documentation.unified-automation.com/uaexpert/1.4.3/html/first_steps.html

Answer 2

If you don't want to deal with certificates then choose then endpoint with SecurityPolicy None when connecting:
Otherwise, note the security directory the example server logs on startup. Something like:
INFO o.e.m.examples.server.ExampleServer - security temp dir: /var/folders/1v/2pxlxd_x4bsdxz25_fv7r0940000gn/T/security
Navigate to the security directory and you'll find the UaExpert client certificate in the pki/rejected folder. You can move it to pki/trusted/certs and then connect with security from UaExpert.