OnReadFile is a TAccessFileEvent property that represents the event handler allowing the TIdTrivialFTPServer instance to service a Trivial FTP Client request to read a file on the local file system. 

Applications must assign a procedure to the OnReadFile event handler to allow responding to the event notification. OnReadFile is used to implement the platform-specific API calls needed to determine access permissions for the client request, and to initialize the stream used for returning the requested file data.

TAccessFileEvent