title: How to determine what's the file type
body: <p>I use ASIHTTPRequest to download file. The url is like <a href="http://www.aaa.bbb.com:8000/showuploaddocument.aspx?docid=45" rel="nofollow">http://www.aaa.bbb.com:8000/showuploaddocument.aspx?docid=45</a>. So I am not able to determine the file type through the url. How can I determine the file type of the downloaded file?</p>