IPVersion is a TIdIPVersion property that indicates the IP address family supported for the socket handle. 

The default value is ID_DEFAULT_IP_VERSION. 

IPVersion is used when the socket handle is allocated using the protocol stack in AllocateSocket, and when establishing the connection to the remote peer in Connect. 

Changing the value in IPVersion causes an EIdCannotSetIPVersionWhenConnected exception to be raised if the socket handle has already been allocated in the Connect method. Use CloseSocket to ensure that an existing socket handle is invalidated before assigning a new value for the IPVersion property.

ID_DEFAULT_IP_VERSION 

TIdIPVersion 

EIdCannotSetIPVersionWhenConnected 

AllocateSocket 

CloseSocket 

PeerIP 

PeerPort