Send Ack Asynchronously

[arpanbose]

I have a chat application which deals with text and image now when sending text message the ack works fine but it the case of image i have created an asynchronous call to know if the image finished saving after that it's triggers. The asynchronous call is working fine but i'm not receiving any ack.

server.addEventListener("message", ChatModel.class,(socketIOClient, messagingObject, ackRequest) -> {
            messagingObject.setDateTime(new Date());
            if (ackRequest.isAckRequested()) {
                if (messagingObject.getMessageType()==MessageType.TEXT){
                    ackRequest.sendAckData(messagingObject);
                }else {
                    targetService.setOnMediaReceived(chatModel -> {
                        System.out.println("ACK");
                        ackRequest.sendAckData(chatModel);
                    });
                }
            }
            targetService.onMessageReceived(messagingObject);
});