What is the format to write to the dataoutputstream of a httpurlconnection?

[#1]

I can write to the flume http source using requests from python. Now i am trying to do similar thing with JAVA. When i try to write to the http source using a dataoutputstream. Nothing is written to the directory designated in flume agent conf. Though i can write to the same hdfs directory when using the python requests. Below is the method i use to do the work.

 public static void sendGet(String ar) throws Exception {
                //r=requests.get('http://192.xxx.xx.21:44444',data=f3.read())
//I get the string and then i try to write to the dataoutputstream of the urlconnection url2(URL of the flume httpsource agent).
// I am able to write using python requests lib to the flume Now i have been trying with Java.
// I dont see any file written to the path defined in the flume agent conf.
//I fear now this may be issue with the data format?
        String url2="http://192.xxx.xx.21:44444";
        URL obj2 = new URL(url2);    
        HttpURLConnection con2 = (HttpURLConnection) obj2.openConnection();
        con2.setRequestMethod("POST");
        //The below line gets printed
        System.out.println("\nSending 'post' request to URL : " + url2);
        con2.setDoOutput(true);
        DataOutputStream wr =null;
          try {
              //This line is also printed.
              System.out.println("Create the stream");
            wr = new DataOutputStream(con2.getOutputStream());
          }finally{
               wr.writeChars(ar);
               //This line is also printed.
                System.out.println("Written");
              wr.close();
            con2.disconnect();
              }
        try{
            System.out.println(ar);
            System.out.println("printed on console");
        }
        catch(Exception e)
        {
            System.out.println(e);
        }
          }

[#2]

This should work:

URL url = new URL("http://192.xxx.xx.21:44444");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("POST");
conn.setDoInput(true);
conn.setDoOutput(true);

OutputStream os = conn.getOutputStream();
DataOutputStream out = new DataOutputStream(conn.getOutputStream());

out.writeChars(ar);
out.flush();
out.close();
os.close();

conn.connect();