Design and Implementation of a Reliable Message Transmission System Based on MQTT Protocol in IoT

Internet of Things is one of most important IT trend and it is getting more popular in home automation fast. A message transmission system is important component in an IoT device for collecting data or send commands. Push protocol is light-weight and high productivity protocol than polling protocol, which is used in IoT devices widely. However, this push message like MQTT protocol is just guarantees of delivery of each message and vulnerable to maintain (the) ordering between messages. Ordering messages and re-sending messages which lost while transmitting are key issue for a reliable message communication system in IoT environment such as home security automation. In this paper, we designed and implemented a reliable message transmission system using MQTT protocol to maintain ordering between messages for the work environment. This (system) consists of MQTT protocol, reliable message transmission server and client module. The reliable message transmission server module expands a message topic to a new message topic after combining the order flag and SEQ. The order flag is the value which determines whether to maintain ordering between the message or not. SEQ is the sequence number for each message and is managed by reliable message transmission system server module and is stored into a database in the server. The reliable message transmission system client module checks message’s sequence before processing the messages and requests the previous message if there are missed messages to retain the messages ordering. For simulation, we implemented the reliable message transmission system with mosquitto MQTT message broker and the simulation showed that this proposed system could enhance the message transmission for IoT environment.