04 Try it yourself Interactive
One message per press. The box in the middle is what is on the wire right now, with its name, its contents and a badge saying whether it is cleartext or encrypted. The panels on either side are what each machine knows so far, with the row that just changed outlined in indigo. The server starts already holding its certificate and its private key; the client starts holding nothing.
Two things are worth waiting for. At the key-agreement step the session key row turns green on both sides at once, and no message on the wire ever contains it. A few steps later the badge flips to encrypted and stays there. Switch to TLS 1.3 to run the same connection with the shares sent up front, and watch the round-trip counter stop at one instead of two. The hostname is yours to change, and it is the value you will find sitting in the clear in message one of both versions. Nothing plays on its own: Next, Back and Reset, or the arrow keys.