typedef void(* MyQttOnMsgReceived)(MyQttCtx *ctx, MyQttConn *conn, MyQttMsg *msg, axlPointer user_data)

Async notification handler called to notify a new message received (MyQttMsg) due to a PUBLISH packet.

ctxThe context where the operation is taking place.
connThe connection where the application message was received.
msgThe message received. This reference is stable during the handler execution. If you need to have a permanent reference that survives to the handler execution grab a reference to it using myqtt_msg_ref (and of course, release that reference with myqtt_msg_unref when no longer needed anymore).
user_dataUser pointer passed in into the function.