procedure Disconnect(
    ASocket: TIdStackSocketHandle
); override;

Disconnect is an overridden procedure that implements the method used to access the protocol stack API method used to close a connection on a socket handle. 

ASocket is the socket handle to be affected by the operation. 

On the Windows platform, the Shutdown() API is called using Id_SD_Send to disable the send portion of the socket descriptor. Other BSD-derived socket implementations (like Linux) use the value Id_SD_Both. 

Disconnect closes the socket handle in AHandle, but may continue to send queued data for a brief period of time based on the Linger options for the socket handle.