OpenProxy is a method used to ensure that an assigned and enabled TransparentProxy for the UDP client is associated with the socket handle in Binding. Use the OpenProxy method, when the TransparentProxy property has been assigned, prior to calling method that send or receive datagrams like Send, SendBuffer, and ReceiveBuffer. 

An EIdMustUseOpenProxy will be raised if OpenProxy is not called prior to reading or writing datagrams when TransparentProxy has been assigned. 

Use CloseProxy to remove the association for the socket handle in Binding on the TransparentProxy server.

Binding 

TransparentProxy 

Send 

SendBuffer 

ReceiveBuffer