Giving some guidelines isn't too much to ask imo
You'd need to do the following steps (might miss one or two, it's early for me
1) Make connection with fileserver where update file is located ( /help /sockopen )
2) On connection, send the file request (HTTP request i assume, so you need to study the HTTP protocol to find out how the request looks like) ( /help /sockwrite )
3) Server will be sending the file-data, store this info in a new file ( /help /sockread /help /write )
4) When filetransfer is completed, close connection ( /help /sockclose )
The idea is pretty obvious but the /help <command> should point you to your way.