Authentication

Hello everyone,
I'm a GSoC participant working for Eclipse Org. this year. As a part of my project , I need to authenticate, upload/download assignments through Eclipse workspace itself. But I'm kinda stuck with authenticating with the moodle server. Basically I need to send HTTP POST Requests through Java (programatically). I do something like this ..

URL url=new URL(loginPage.getServerURL().toString()+"/login/index.php");
URLConnection con=url.openConnection();
con.setDoInput(true);
con.setDoOutput(true);
con.setUseCaches(true);
//con.setRequestProperty("Content-Type", "text/html");
DataOutputStream out=new DataOutputStream(con.getOutputStream());
String test=new String("username="+URLEncoder.encode("admin","UTF-8")+
"&password="+URLEncoder.encode("admin","UTF-8"));
out.writeBytes(test);
out.flush();
out.close();

Similarly , I get the output, after sending the request by:

DataInputStream in=new DataInputStream(con.getInputStream());
String buf;
while(null!=((buf=in.readLine())))
{
System.out.println(buf);
}
System.out.println(con.getURL());
in.close();

Well, unfortunately the above code takes me back to the moodle's homepage with a unsuccessful login. If I change the values of the username or password, I get the "Invalid username or password" error as expected in the output page. But with correct values it still doesn log in. I wonder if it has to do anythin with the cookie requirements ? Help needed ...

Thanks ,
Souvik