When running an application using JNBridgePro, you get a SocketException with the message: "No connection could be made because the target machine actively refused it".

This means that the .NET side can't communicate with the Java side. Either you have forgotten to start the Java side, or you have incorrectly configured either the .NET or Java sides so that they cannot find each other.

To address this problem, make sure that you have started the Java side. If you have, then make sure that the .NET side is configured to contact the Java side on the correct machine, and using the port on which the Java side is configured to be listening.