Hi,

The part for the ApplicationURI is defined from hostname of the machine on it is run. This is because in OPC UA each server must have network-unique ApplicationURI and hostname fulfills this purpose.

One reason why this error could happen if for some reason the hostname could not be determined. Another is that currently the check validates that the String “localhost” does not exist in any part of the ApplicationURI, i.e. if you were to happen to have hostname literally e.g. as “localhost2”, it would cause the problem.

Due to one workaround we have in the (java) SDK which is used to make the application is if java call

fails, then it just uses “localhost” (so it causes this if it fails, could probably be better…). It does log a WARN level log if this happens. However in it’s current release version the software only displays logs in the “Debug Log” tab, which is not that convinient, but maybe you could check if anything is shown there.

Alternatively it is possible that something is broken in the newest CentOS. Additionally seaching e.g. https://stackoverflow.com/questions/1881546/inetaddress-getlocalhost-throws-unknownhostexception might provide some solutions.

We will try to reproduce the problem here as well.