DotNetGateway port already in use

We have some productions in Ensemble that uses DotNetGateway to use dll created with .Net. The DotNetGateway is configured with a port number, and then the operation uses that port.

But sometimes, suddenly Ensemble answers that the port is already in use, but it is only used by the DotNetGateway. And the only way to resolve this and make the port available again, is to restart the full server. We have tried to restart Ensemble, to kill the process that may be using the port and nothing. Is there any way to make a DotNetGateway port "stay connected" or 
something to search who is occupying the port and release it?