Once a conversation is established, a client can make one or more requests for data in a particular format through the ESL DDE DLL subroutine calls, and can respond to the events invoked upon receipt of that data.

A server will generally not voluntarily call DDE DLL subroutines and functions to send data; instead it will only do so in response to events invoked when a client partner requests data. An exception to this rule is a server that is capable of supporting an advise state.