This is kind of a loaded and open ended question. Without knowing something about the architecture, or what your goals are it's hard to answer. Is this for a w

This is kind of a loaded and open ended question. Without knowing something about the architecture, or what your goals are it's hard to answer. Is this for a web page or web app, native iOS/Android app, desktop app? Is this for Client/Server or P2P? Are you sending files that can be encrypted, or is it a real time connection link of some sort? In general, you can use TLS/SSL (as mentioned by @bigiain), but there are other use cases where you might want to do something more specialized.