These are the steps for a client connection:
1.Client initiates a connection to the database so it connects to the listener
2.Listener starts (fork) a dedicated database process that will receive this connection (session)
3.After this dedicated process is started, the listener passes the connection from the client to this process
4.The server process takes the connection from the listener to continue the handshake with the client
5.Server process and client exchange information required for establishing a session (ASO, Two Task Common, User logon)
6.Session is opened

这个解释的挺好的，不过听说windows的连接建立方式不太一样。

谢谢！