What is the meaning of "host crossdomain.xml from port 843"?

How is a file hosted on one particular port vs another port? In order to get my flex program to do anything, even on localhost, I apparently have to accomplish this, but although I know how to FTP my crossdomain.xml to my GoDaddy server, I don't even begin to understand the meaning of hosting it on port 843. I don't even know where to start. Can 开发者_StackOverflowanybody here even get my foot in the door?

Thanks in advance.

It means that you need to create a website that listens to that port, and then serve the file from that website.