Apps Transfer files wirelessly in a program?


I need to implement a portion of a program that can send and receive files wirelessly from a computer. I know that there are many programs that can do this in the market, but I can't find anything explaining how it can be done.

It doesn't particularly matter the method used to transfer the files. I've looked at wifi/ftp and bluetooth both, but can't figure out how either of these can be implemented without a third party program. Anything that points me in the right direction would be greatly appreciated. Thanks!