Hacker News Reader

Comment by dfox | Hacker News Reader

For the case of ssh versus ssl the detection is trivial: first message for ssl comes from client but for ssh first message comes from server. So server simply waits for a while and assumes that client speaks ssh when it does not receive anything.

One can also match whatever is received in first message from client against known protocols (this approach makes it possible to for example run HTTP and HTTPS on same port as is done by IPP servers, particularly CUPS).

View on HN

What do you mean by:

       first message for ssl comes from client but for ssh first message comes from server

With SSL/TLS, the client connects and sends a ClientHello message first, and then the server responds; with SSH, the server will send a version string upon connection (and expects the client to do the same). With plain HTTP, the client sends the request first. The server can detect which one of these cases it is.

I'm still being not clear of what you mean by:

>with SSH, the server will send a version string upon connection (and expects the client to do the same).

Say for example if I do:

   ssh some.machine.com

I'm (being the client ) call the ssh port ( server ) running on the some.machine.com, right? If thats the case, client is who starting the conversation right?

Correct me if I'm wrong.

Establishing a connection isn't considered 'sending a message'.

Oh ok. Now I understood, thanks.

Reply on news.ycombinator.com