How can I determine the server is waiting for input in POE::Wheel::ReadWrite?

I worte a POE job server,  just like what
http://poe.perl.org/?POE_Cookbook/Job_Server do.
when I use POE::Component::Client::TCP to write a interactive client, I
found I can not determine when is the end of a command.

ServerInput callback of POE::Wheel::ReadWrite can be used to get all the
output of the command, it is line-based, but I want to input anther command
when the server output is over, I definitely can not yeild a callback
whenever a single line from server comes to  the server. So how can I
determine the end of the command output from the server?

here is my simple client code.
http://gist.github.com/234347

thanks
-- 
Woosley.Xu