In this paper, we demonstrated a service robot navigation system based on the Message Queuing Telemetry Transport (MQTT) protocol communication system that updates the real-time robot states for multiple users. The proposed office assistant robot (OABot) consists of a navigable structure, a mobile app, and a central control workstation and these three components intercommunicate via a wireless network. The voice-recognition mobile app is used to interact with users with voice commands; these

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... ce commands are processed inside the workstation and actions are assigned to the moving robot accordingly. The robot can navigate inside the room using real-time maps while localizing itself in the environment. In addition, the robot is equipped with a digital camera to identify people in predefined locations in the room. The WiFi communication system is provided with RESTful and Mosquitto servers for better human-robot communication. Hence, multiple users are notified about the robot status through updates on the real-time states via the MQTT protocol. The developed system successfully navigates to the instructed destinations and identifies the target person with an average accuracy of 96%. Most importantly, in an isolated indoor environment with social distancing restrictions to perform, the proposed system is essentially useful for contactless delivery.