A method is described for setting up a communication between a device (R1;R2) and a host application (A11; A12; A21; A22) over an IP network, where this device has no externally known IP address. The method includes the steps of: a. sending out a multicast discovery request by the host application to a specific multicast address and a specific port known by the device; b. the device responding to the discovery message with a multicast discovery response to the specific multicast address and specific port number, the discovery response including a unique identification parameter proper to the device and the host IP address and application port number; c. the host application accepting this identification message based on the host IP address and application port number and sending subsequent multicast messages to the specific multicast address and specific port and including the identification parameter; d. the device accepting the subsequent multicast messages based on the identification parameter and sending subsequent multicast messages to the specific multicast address and specific port and including the identification parameter and the host IP address and application port number.