How to upload file through objective C?

I want to ask a question about the objective C on iPhone. I want to upload a file (actually I store all the data in a NSString) to a server. However, I have not idea of how to do, I have checked the website of the Apple Developer, and I know there are a function called开发者_Go百科 connection:didSendBodyData:totalBytesWritten:totalBytesExpectedToWrite:, but it seems wrong. Can anyone help me and provide some sample code to me? Thank you very much.

I found this is the answer http://cocoadev.com/index.pl?HTTPFileUpload