TIdCmdTCPClientListeningThread = class(TIdThread);

TIdCmdTCPClientListeningThread is a TIdThread descendant that implements a listening thread for TIdCmdTCPClient. 

TIdCmdTCPClientListeningThread provides properties to access both the client for the listening thread and data read from the peer connection for use in command handler in the client. 

TIdCmdTCPClientListeningThread includes an overridden Run method (protected) to read data from the peer connection, and to dispatch the received data to command handlers in the TIdCmdTCPClient client. 

TIdCmdTCPClientListeningThread is the type used to implement the listening thread member variable in TIdCmdTCPClient. TIdCmdTCPClient creates the listening thread when the Connect method is called.