连接didReceiveData在iphone中发布Url时调用了两次？

I am new to iphone development.I have posted the URL with the user-name and password. I am able to print the data in "connection didReceiveData " method.But i see "connection didReceiveData" method called twice.I don't know ,where i am going wrong. Here is my codeI am new to iphone development.I have posted th