Abstract: Communication through an intervening firewall can be achieved by transmitting an outbound datagram through a port of a firewall to open a circuit through the firewall, receiving an inbound datagram through the open circuit from an application, wherein the application is external to the firewall, and communicating with the application through the open circuit. Also, the application can comprise a client application and the firewall can comprise a server firewall. Further, the client application can transmit an outbound datagram through a port of an associated client firewall to open a circuit through the client firewall and can receive one or more datagrams through the open circuit of the client firewall. Additionally, the port of the server firewall and the port of the client firewall can correspond to the same port number.