TIdCmdTCPClient = class(TIdTCPClient);

TIdCmdTCPClient is a TIdTCPClient descendant that implements a TCP-based client using command handlers. Command handlers allow the client to respond to data received from the peer connection by performing specific processing or sending responses based on values in the data. 

TIdCmdTCPClient also implements event handler properties to allow the client to perform operations both prior to and following execution of a command handler. 

TIdCmdTCPClient uses a listening thread as specified in TIdCmdTCPClientListeningThread to read data from the peer connection and to execute the command handlers in the client. TIdCmdTCPClient overrides method from the ancestor class to create and destroy the listening thread when the connection for the client is opened or closed.