Method for permitting two parties to establish connectivity with both parties behind firewalls

摘要

A communications scheme enables a central communications station to assist two communications systems located behind firewalls that prevent communication initiated from an external data network to establish direct communication with each other. In one embodiment, the systems separately establish communications with the central communications station and obtain from it the connection information (e.g., IP address, port, etc.) of the other. The systems then directly communicate with each other using the obtained connection information while pretending to be the central communications station. In another embodiment in which the firewalls include NAT devices that implement network address translation, the systems exchange connection information for establishing a new connection through the central communications station and then complete a three-way handshake with the assistance of the central communications station, thereby allowing the central communications station to remove itself from the communication.