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HTTP Range Header

There was a huge attack on our infrastructure couple of days before. It didnt follow the regular pattern. So did a lot of googling (google verb!) but eventually we were not to able to successfully find the intricacies employed in the attack. During this literature reference, I came across Partial Get feature in HTTP header. This is the feature used by Download Managers like IDM by spawning multiple threads to download a file. The partial Get request specifies the byte ranges it requires to download.
Eg

GET / HTTP/1.1
Host: 127.0.0.1
Range: bytes=0-89

The request requires first 89bytes of the file. There can be more than one chunk requested in the range header. The webserver responds with a 206 code for partial GET.

I have coded a primitive threaded downloader which spawns 10 threads, downloads 10 different chunks of a big file and unite them as a single file. Committed the initial version at github https://github.com/kalyanceg/downloader/blob/master/curler.java. Please do feel free to checkout the code (I will add documentation soon) and develop UI/more feature over it.

To view a demo, checkout the code and run
 java curler <input url>. 
Note: No output will be displayed on the prompt. Will add them to improve usability. Once the program finishes, the file would be downloaded in the same directory where the code is.

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