problem about judge the server state

[h ch]

first when connect_server execute ,the server's state is unknown, and when read_handshake execute we can check the server's state ,the server connected that we can point in connect_server,or just let mysql-proxy do automately ,my question is when in read_handshake we read the server state is up, but after a while ,the server actually down, how can the mysql-proxy know that the server's state is change?
and the read_handshake execute just once for each connection ,that means i need check the server state in read_query function? but the value of server's state is really the server's state that the moment i check?