Techniques for translating between logical addresses and ports of a first network, and logical addresses and ports of a second network connected to the first network at an intermediate device include receiving a first packet at the intermediate device from a first device having a first address on the first network. A second packet is sent to a second device on the second network in response to receiving the first packet. The second packet includes, in a source address field, a particular address of the intermediate device on the second network. It is determined whether the first packet includes a resource registration message that registers a first resource on the first device with a protocol server for a particular protocol. The protocol server is available at the second device on the second network. If the first packet includes the resource registration message, then information in the resource registration message for uniquely requesting the first resource is determined. The first information is stored in a first data structure in association with the first address. As a result, network address and port translation (NAPT) functions in a system using NetBIOS protocol.