How to accept messages from the dedicated server during the loadmap phase

Hello everyone, I have a problem. When loading the map, the main thread will be blocked and unable to receive DS messages. I used fdefaultmovie player to create a loading screen, Update the loading progress of local and other players in real time. The loading progress needs to be synchronized by the server to all players. I use asynctask to send progress information to DS in the main thread. The server can receive it, but the client can’t receive the message sent by the server when loading. I used NMT_Gamespecific to send the message to server , do you know how to solve this problem