I had the problem when I used that override:
public ForwardedPortLocal(uint boundPort, string host, uint port);
public ForwardedPortLocal(uint boundPort, string host, uint port);
var port = new ForwardedPortLocal(27017, "127.0.0.1", 27017);
var port = new ForwardedPortLocal("127.0.0.1", 27017, "127.0.0.1", 27017);