Class Downloader

java.lang.Object
   |
   +----Downloader

public class Downloader

extends Object

NetRand Project

Software Engineering - CS536

University of Wisconsin - Milwaukee

Authors:

• Spring 1998 - Francis William Kasper

Downloader calls the BinaryLinkExtractor to extract all the links to binary files in a given HTML document. After a list of binary file links is obtained, it places them on a stack. Each file on the stack is downloaded eight consecutive times. The time it takes to download the file is examined. If it is an even number, a 0 bit is recorded, otherwise a 1 bit is recorded. One byte of entropy is obtained from each binary file link.

binaryFileLinks

a stack to hold the binary file links

Downloader()

collectBinaryFileLinks(String)

collects all the binary file links for a HTML referenced by a given URL

doDownload(String)

calls getBinaryFile to perform the downloading of the binary file; downloads the binary file eight consecutive times; from these times it records a 0 bit if the download time was even, otherwise a 1 bit is recorded.

getBinaryFile(URL)

performs the actual downloading of the binary file

getEntropy(String)

calls the appropriate functions to extract the binary file links from the HTML file referenced by the given URL, perform the downloading and sending of the random bytes.

 private Stack binaryFileLinks

a stack to hold the binary file links

 public Downloader()

 public void getEntropy(String urlString)

calls the appropriate functions to extract the binary file links from the HTML file referenced by the given URL, perform the downloading and sending of the random bytes.

Parameters:

urlString - - the URL to reference the target HTML file

 private void collectBinaryFileLinks(String urlString) throws Exception

collects all the binary file links for a HTML referenced by a given URL

Parameters:

urlString - - the target URL

Throws: Exception

is thrown if the given URL cannot be accessed

 private void doDownload(String urlString)

calls getBinaryFile to perform the downloading of the binary file; downloads the binary file eight consecutive times; from these times it records a 0 bit if the download time was even, otherwise a 1 bit is recorded. It uses the BitSender class to send the random byte to the server

Parameters:

urlString - - the target binary file

 public long getBinaryFile(URL target)

performs the actual downloading of the binary file

Parameters:

target - - the target URL to download

Returns:

the download time is milliseconds