IdStack

TIdPacketInfo is a TObject descendant used to store information about the hop count, source, and destination for packets read and written using the API methods for the protocol stack. 

TIdPacketInfo stores values that identify the IP address, port number, and network interface used for both the host sending the packet (source) and the remote endpoint (destination). when sending packets, the values in the SourceIP, SourcePort, and SourceIF properties all refer to the local computer system. When receiving packet transmissions, the values in the SourceIP, SourcePort, and SourceIF properties all refer to the remote endpoint for the transmission. 

In addition, TIdPacketInfo captures the TTL (Time-to-live) value that indicates the number of hops required to complete the packet transmission. 

TIdPacketInfo instances are used as an argument in the ReceiveMsg, ReceiveFrom, and SendTo methods in TIdStack and descendant classes.

TIdStack.SendTo 

TIdStack.ReceiveFrom 

TIdStack.ReceiveMsg