Boolean - True when the connection is open, or data exists in the Indy buffer.

Connected is a Boolean function used to indicate that connection for the IOHandler has been established, and that the internal buffer is assigned or contains existing data. 

Connected calls CheckForDisconnect to synchronize properties that reflect the connection state of the transport for the IOHandler. 

The return value for the function is True when the InputBuffer contains exisiting data, or when ClosedGracefully is False and the InputBuffer is assigned. 

Connected is used in ReadStream and AllData to determine if unread data in InputBuffer should be handled or more data read from the transport for the IOHandler.

TIdIOHandler.ClosedGracefully 

TIdIOHandler.InputBuffer