A method for establishing a data packet exchange communication session that allows the exchange of data packets between an originating client and a destination client in a data network having a client-server arrangement is provided. An originating client transmits communications session request data message to a communications management server via a first temporary signaling communications path. The communications session request data message contains at least a unique network address of a destination client. The communications management server, upon determining that said originating client is residing behind a first network firewall, determining whether said first network firewall will allow exchange of data packets between said originating client and any other client not residing behind said first network firewall. If it is determined that the first network firewall will allow exchange of data packets between said originating client and any other client not residing behind the first network firewall, the communications management server retrieves relationship information between said unique network address of said originating client and said unique network address of a first network firewall port and a first network firewall port identity, and establishes a data packet exchange communications session with said communications management server through said first network firewall. Otherwise, said communications management server, upon receiving a media packet communications session request data message from said originating client via said first temporary signaling communications path establishes a media packet exchange session with said originating client via said first network firewall.