A universal, unique identifier (UUID) identifies a specific application. The developer of a specific application assigns the UUID to that application. (See UUID in Chapter 3 for details on how to obtain a UUID.) Any application (whether it is the specific application or not) can use that UUID when it establishes a file transfer session using the xfInitialize function, if it can transfer files for the specific application. An application that can transfer files for more than one specific application is able to support multiple UUIDs.