Binding is a read-only TIdSocketHandle property that represents the socket descriptor used in TIdSimpleServer to Listen for serial connection requests. 

When reading the value in Binding, access is redirected to the Binding in the TIdIOHandlerSocket assigned to the IOHandler for the server. 

Binding is allocated in the CreateBinding method. 

Binding is used when TIdSimpleServer when BeginListen is called to begin listening for connection requests. If Binding is not assigned, the Binding is initialized using CreateBinding. 

Binding is also used when the binding the specified values in BoundIP and BoundPort for the socket connection.

TIdSocketHandle 

TIdIOHandlerSocket 

TIdSimpleServer.Listen 

TIdSimpleServer.CreateBinding