If this value is true and the java.rmi.server.disableHttp system property is not set, then RMI's default socket factory will fall back to HTTP tunneling when any java.net.SocketException is thrown from an initial (direct) connection attempt, as opposed to the default behavior of falling back to HTTP tunneling only if an initial connection attempt throws a java.net.UnknownHostException or java.net.NoRouteToHostException.
This setting can be useful when dealing with firewalls that deny (instead of ignore) connection attempts to unauthorized ports, resulting in java.net.ConnectionExceptions inside the client's default RMI socket factory. If this system property is not enabled, then such ConnectionExceptions will not trigger HTTP fallback, since they are neither UnknownHostExceptions nor NoRouteToHostExceptions. However, if this system property is enabled, then the ConnectionExceptions will cause HTTP fallback to occur, because ConnectionException is a subclass of SocketException.