Error #2124: Loaded file is an unknown type. when access file from remote server

Hi,

        I used a Loader with URLRequest to load an binary file from remote server, while it shows an error message of "Error #2044: Unhandled IOErrorEvent:. text=Error #2124: Loaded file is an unknown type." after the request is complete. The file stores an non-standard data type, which consists of first 4bits as constant characters "SCJ1", then the next 60 integer(4-byte) and 60 JPEG image file with 60 integer for image size.

        For example, if I want the fifth image data, I can access the 21st ~24th characters as follows,

   "SCJ1           0000       1111          2222          3333               4444 ...."

                         first        second        third          fourth               fifth

and then I need to go to the position of 0x4444. This position stores the size of the target image, so I need to extract the amount of bytes from the next byte.

Is there any method to load such a user-defined data by actionscript?