iViewer sends custom headers along with all HTTP requests to help identify where the request is coming from. The exact headers that are sent differ depending on the context of the HTTP request.
When iViewer requests a GUI File to reload, along with the HTTP request it will send the following HTTP Headers:
cf-client-version: v4.0.254 build 254
cf-client-screensize: width,height (when device is in portrait orientation)
cf-hardware-os: iPhone OS
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.
User-Agent: iViewer 4 4.0.280 rv:280 (iPhone; iPhone OS 6.1.4; en_AU)
The app name, version and device details will match the details of the mobile device and app being used at the time to make the HTTP request.