Timed HTTP upload via openConnection

Question

Hi there,
I've been trying to perform a HTTP POST request which sends as much of a large payload as possible, recording how much is uploaded, within a given timescale.
write() and flush() within my while loop do not seem to write any data to the socket however, and the console doesn't suggest any errors were encountered. 'data' has many megabytes of data to upload.
Would welcome any ideas?
BP
//Init
threadTimeStart = System.currentTimeMillis();
theadTimeStop = threadTimeStart + 10000; // 10 seconds
int writtenByteCount = 0;
// Open connection
URL u = new URL("http://hostname/filepath");
URLConnection uc = u.openConnection();
uc.setDoOutput(true);
// Write data
OutputStreamWriter wr = new OutputStreamWriter(uc.getOutputStream());
// BufferedWriter wr = new BufferedWriter(new OutputStreamWriter(uc.getOutputStream())); // has been tried also
String data = URLEncoder.encode("upload_data", "UTF-8") + "=" + URLEncoder.encode(data, "UTF-8");
while ( writtenByteCount < data.length() ) {
     wr.write(data, writtenByteCount, 1024);
     wr.flush();
     writtenByteCount += 1024;
     System.out.println("writtenByteCount: " + writtenByteCount + " of maximum " + data.length() + " bytes" );
     if ((double) System.currentTimeMillis() > TimeStop) break;
// Get response
BufferedReader br = new BufferedReader(new InputStreamReader(uc.getInputStream()));
String line = null;
while ((line = br.readLine()) != null) {
     // **process response**
// Close connections
wr.close();
br.close();

Answer 1

Since your URLConnection will be an HttpURLConnection you can cast it to an HttpURLConnection and use method
HttpURLConnection#setChunkedStreamingMode(1024); // Or whatever chunk size you want.