Abstract: A method for operating a communication device is disclosed. One embodiment includes the steps of: generating an intermediary key corresponding to peer to peer (P2P) communication between a client and a counterpart client; transmitting the intermediary key to the counterpart client; obtaining an intermediary path corresponding to the intermediary key; receiving the data through the intermediary path from the client that did not receive an acknowledgement for data transmitted to the counterpart client because of a change of a network address of the counterpart client; and transmitting the data to the counterpart client if the counterpart client accesses the changed network address by using the intermediary key.

Abstract: A method for operating a communication device is disclosed. One embodiment includes the steps of: generating an intermediary key corresponding to peer to peer (P2P) communication between a client and a counterpart client; transmitting the intermediary key to the counterpart client; obtaining an intermediary path corresponding to the intermediary key; receiving the data through the intermediary path from the client that did not receive an acknowledgement for data transmitted to the counterpart client because of a change of a network address of the counterpart client; and transmitting the data to the counterpart client if the counterpart client accesses the changed network address by using the intermediary key.

Abstract: Disclosed is a method for operating a server supporting peer-to-peer communication. One embodiment comprises the steps of: issuing a public key in response to a public key request received from a client and transmitting the public key to the client; receiving a private key from the client and mapping the public key and private key as a key pair; receiving, from the client, a request to generate an identifier comprising one or more items of unique information of the client; generating an identifier corresponding to the client in response to the request to generate an identifier, generating a security key utilizing the unique information, and transmitting the identifier and security key to the client; receiving, from the client, an authentication request comprising the identifier and security key; and authenticating the client in response to the authentication request and transmitting the authentication result to the client.