Security System - send message like TCP/with confirmation

[siod]

Hi Guys,

I´d like to setup a home security system based on MySensors using MQTT. Because a security system must be 100% reliable I must confirm that a message like "Door opened" reaches first: the gateway, second: the controller (openhab in my case).
From my point of view this can only be achieved if the sensor is not only sending the info about the open/closed state of a door, but also receives an acknowledge that the sent messages received the Controller, because that´s the point where the user gets the info from. So the node should send the state message again and again until it receives the info like "message reached controller, stop sending now".
Any idea how I can realise this? I´ve read a lot about "ACK" but I don´t think that´s what I need!? Thanks in advance!