DataAvailList is a read-only TIdSocketList property that contains socket handles with data available for the proxied client connection. 

DataAvailList is updated and used during execution of the TIdMappedPortContext task to contain the TIdSocketHandle instances that have data available for reading by the local client Connection or the OutboundClient for the proxied session. 

When DataAvailList contains the socket handle assigned to the IOHandler for the local Connection, data is read from the connection and stored in the NetData property for subsequent use in the OnExecute event handler for the context. Non-blank values in NetData are then written to the OutboundClient. 

When DataAvailList contains the socket handle assigned to the IOHandler for the OutboundClient connection, data is read from the connection and stored in the NetData property for subsequent use in the OnOutboundData event handler for the context. Non-blank values in NetData are then written to the local client Connection. 

Use ReadList to access the socket handles for the local connection and the outbound client connection regardless of data availability.

NetData ReadList Connection OutBoundClient TIdSocketHandle TIdMappedPortTCP.OnExecute TIdMappedPortTCP.OnOutboundData