Why http socket return -1

Question

I use HttpURLConnection class to submit a list of values to a servlet,
When I use application to do that,it works.But after I change it to
a servlet,it failed.getResponseCode() return -1 not 200,why?

Answer 1

public void SubmitToParty(String reqMethod,String URLStr,String Content)
try
URL UrlInst = new URL(URLStr);
URLConnection MyConn= UrlInst.openConnection();
HttpURLConnection HttpConn = (HttpURLConnection)MyConn;
if(reqMethod.compareTo("GET")==0||reqMethod.compareTo("POST")==0)
HttpConn.setRequestMethod(reqMethod);
HttpConn.setDoOutput(true);
PrintStream out = new PrintStream(HttpConn.getOutputStream());
out.println(Content);     
out.close();
System.out.println(HttpConn.getResponseCode());
System.out.println("send data ok!");
catch(Exception URLExp)
System.out.println("Submit to party error!");
URLExp.printStackTrace();
}