Method, system and apparatus for providing services across networks

The invention provides a method and a system for providing a service from a network device in a closed network to a client device outside of the closed network through a service portal. The method may include the steps of actively establishing a first connection between the network device and the service portal, receiving a request for the services from the client device via established first connection, retrieving data of service and sending back to the client device. As a result, the client device may access the service of network device in the closed network without being blocked by firewall or other security mechanism of the closed network. In addition, the service portal may also validate the client device, and therefore malicious intrusion or insecure access may be prevented.