A communication system for establishing a P2P connection is disclosed, wherein the communication system comprises: a networked device or service device having an identification; a linking server for providing connecting information to enable a terminal device or client device to establish a P2P connections between the service device and the client device, wherein the identification of service device is registered in the linking server, wherein the client device communicates with the link server to establish a P2P connection to the service device according to the connecting information provided by the linking server, wherein the client device has not been registered into the linking server when the P2P is established. In addition, A UID (Unique Identification) can be embedded in a processor, wherein the UID can be stored in a non-volatile memory device inside the processor and the UID will be programmed and tested after the processor is fabricated, so that it can be readily used for establishing A P2P connection.