Creating A Chat?

Hi Guys, I have created few chats in the past, but I'm trying to create a new one which saves on HTTP requests and do not become an overkill to the server as more users get in. The chat is a one on one, I'm trying to achieve this: * A user sends a message * The message is not saved/save temporarily on the server * The message is showed to the other user Any ideas how i should implement this? I have no idea how to build it in the most efficiency way, any notes or recommendations or anything that I should pay attention to during development will be very appreciated.