Device and method for interconnecting two subnetworks

An interconnection method for interconnecting first and second sub-networks, said first and second sub-networks being adapted for enabling UPnP devices to be connected thereto, each UPnP device comprising at least one server associated with an IP address and a port number, wherein an interconnection device interconnecting said first and second sub-networks performs the following first steps in the case where the interconnection device detects the presence of a UPnP mobile terminal:

• subscribing, on both the first and second sub-networks, to a predefined IP address and port number to which multicast UDP datagrams transmitted during a UPnP discovery phase are sent,
• listening out for UDP datagrams transmitted to said predefined IP address and the port number allocated by the interconnection device to said server;
• and after said first steps, the interconnection device performs:
• determining, for said first and second sub-networks, actual IP addresses and port numbers of servers of UPnP devices from received frames representative of discovery messages transmitted by said UPnP devices;
• allocating a different port number to each one of said servers and storing in a list the actual IP address and port number of each one of said servers in correspondence with the port number allocated to said server by the interconnection device and the IP address of the interconnection device usable on the sub-network other than the one to which the server is connected;
• establishing, upon receiving a connection request corresponding to a port number allocated to one of said servers by the interconnection device, a connection between the interconnection device and said server, and a connection between the interconnection device and the UPnP device that sent said request, the interconnection device performing a relay between these connections;
• and, in at least one frame sent from the first sub-network and received by the interconnection device via one of said connections, the interconnection device having two IP addresses for communicating between the first and second networks, a first IP address being used for routing frames in the first sub-network and a second IP address for routing frames in the second sub-network:
• modifying the received at least one frame by replacing each actual IP address and port number of a first server belonging to the first sub-network with the second IP address of the interconnection device that is associated with the second sub-network and the port number allocated to said first server;
• modifying the received at least one frame by replacing each IP address of the interconnection device associated with the first sub-network and the port number allocated to a second server belonging to the second sub-network with the actual IP address and the port number of said second server determined from said list;
• and
• transmitting said frame thus modified over a sub-network chosen among the first and second sub-networks, the chosen sub-network being the one from which the interconnection device has not received said frame.