Operation of the Server
When the server is started, it begins to listen to a port for a socket. The default
port is 22, a well-known port for Secure Shell. This can be changed to
suit any custom environment—however, make sure that no other process is using
the port you are planning to use.
The Secure Shell daemon can also be started from the Internet daemon
inetd. For the purpose of this text, it is assumed that
sshd2 is not invoked through inetd but started on its own.
When the daemon is listening for a socket, it waits until a
client initiates a socket connection. Once connected, the
daemon forks a child process, which in turn initiates key
exchange with the client. The child process handles the actual
connection with the client, including authentication, supported
cipher negotiation, encrypted data transfer, and termination of
the connection. After the connection has been terminated, the
child process terminates as well. The parent process continues
listening for other connections until explicitly stopped.
