In controller "UploadController.groovy"
-----------------------------------------------

def test() {
    InputStream inStream = request.inputStream
    
    if(inStream != null) {
        int read = 0;
        byte[] buffer = new byte[4096];
        long total = 0;
        
        println "Start reading"
        
        while((read = inStream.read(buffer)) != -1) {
            println "Read " + read + " bytes from input stream buffer"      //<-- this is NEVER called
        }       
        
        println "Reading finished"
        println "Read a total of " + total + " bytes"   // <-- 'total' will always be 0 (zero)
    } else {
        println "Input Stream is null"      // <-- This is NEVER called
    }
}


In Java client
-----------------------------------------------

public void connect() {
    final URL url = new URL("myserveraddress");
    final byte[] message = "someMessage".getBytes();        // Any byte[] - will be a file one day
    HttpURLConnection connection = url.openConnection();
    connection.setRequestMethod("GET");                     // other methods - same result
    
    // Write message 
    DataOutputStream out = new DataOutputStream(connection.getOutputStream());
    out.writeBytes(message);
    out.flush();
    out.close();
    
    // Actually connect
    connection.connect();                                   // is this placed correctly?
    
    // Get response
    BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
    
    String line = null;
    while((line = in.readLine()) != null) {
        System.out.println(line);                   // Prints the whole server response as expected
    }
    
    in.close();
    
}