Android : Android fails to url.openConnection() for some links and I can't see source to tell why - HttpURLConnectionImple "source not found"

I am trying to fix bug, when some files can't be downloaded. I located that urlConnection = (HttpURLConnection) url.openConnection(); (from code below) sometimes return HttpURLConnection object with connected = false.

However I can't look into as for HttpURLConnectionImpl i get "source not found" in Eclipse

private byte[] getFromHttp(String urlString) {
    HttpURLConnection urlConnection = null;
    BufferedOutputStream out = null;
    FlushedInputStream in = null;

    try {
        final URL url = new URL(urlString);
        urlConnection = (HttpURLConnection) url.openConnection();
        InputStream is = urlConnection.getInputStream();
        in = new FlushedInputStream(new BufferedInputStream(is, IO_BUFFER_SIZE));
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        int b;
        while ((b = in.read()) != -1) {
            baos.write(b);
        }
        return baos.toByteArray();
    } catch (final IOException e) {

Of course I have tried to attach sources for used Android 4.2 (android-17) from my D:\adt-bundle\sdk\sources\android-17. Eclipse-ADT does not take it.