雖然現在全世界都在用 OpenSSH，但當初 SSH 其實是 SSH Communications Security 所發展出來的。最近上面在講當初申請 port 22 的故事：「How SSH Port Became 22」。
選 port 22 是因為剛好要取代 port 21 的 ftp 與 port 23 的 telnet：
Anyway, I designed SSH to replace both telnet (port 23) and ftp (port 21). Port 22 was free. It was conveniently between the ports for telnet and ftp. I figured having that port number might be one of those small things that would give some aura of credibility. But how could I get that port number? I had never allocated one, but I knew somebody who had allocated a port.
而後來就寫信去要 port 22 這個位置...