When iViewer requests a GUI File to reload, along with the HTTP request it will send the following HTTP Headers:

• cf-client: iViewer
• cf-client-version: v4.0.254 build 254
• cf-client-screensize: width,height (when device is in portrait orientation)
• cf-hardware: iPad
• cf-hardware-os: iPhone OS
• cf-hardware-os-version: 6.1.3
• cf-hardware-uuid: device ID here (if iOS allows applications access, otherwise it's the same as cf-uuid)
• cf-uuid: new unique identifier used by CommandFusion for device registration (due to Apple removing access to hardware ID in iOS 6+ releases)
• cf-new-udid: This header is being phased out in future iViewer versions. Same as cf-uuid.
• cf-old-udid: Depending on the access level iOS offers applications, this could contain the hardware ID or the CommandFusion device ID.