The invention relates to a method of transmitting a message from a wireless radio-frequency short-range communication network (20) via a gateway (21) to a network (14, 24) external to the communication network (20). The method comprises receiving a first message (41) via a short-range radio link at the gateway from a terminal device (23) of the short-range communication network (20), the first message being addressed to an element (25, 34) external to the short-range communication network, and the first message comprising a network address of said terminal device as a transmitter's address and a first port number as a source port number, the network address of the terminal device being used inside the short-range communication network. The method comprises allocating a second port number to the terminal device, replacing said network address of the terminal device in said first message (41) with the network address of the gateway and the first port number with said second port number, generating the correlation of the network address of the terminal device, the first port number and the second port number and storing said correlation in a memory available to the gateway for identification of the terminal device. The method comprises transmitting the first message from the gateway to the element external to the short-range communication network (20) with said replaced information. The invention also relates to a gateway and to computer software.