When the client connects to the server it asks the server first for available endpoints. The server should report back with a set of endpoints, which again contain the hostname to connect to.
If the server reports back with a hostname which the client cannot look up, it is currently not possible to connect to the server with camel-milo.
I did prepare a PR which adds a boolean flag to the endpoint, allowing to override the host of reported endpoint with the one originally provided. This is disabled by default, but can be enabled when necessary.