Message Delivery system

This is a message retrieval and posting system implemented in C. Implementation is done similar to MQTT protocol which is a common protocol used for IoT applications.

Implementation

• Components -

  1. Broker - Server for storage of messages posted by the publisher. There have to be a minimum of 2 brokers connect to eachother in a circular network. Messages can be posted to any of the brokers and retrieved from any other. Every Broker on the system has a unique broker_id that it uses to identify itself.
  2. Publisher - client that provides interface to post messages to the broker. It has interface to create a topic on the broker. Messages are published under a topic.
  3. Subscriber - client that provides interface to read messages from the brokers. Any subscriber first has to subscribe to a topic before reading any messages under it.

• General Struct Definition -

typedef struct my_struct{
    int type;
    char message[512];
    char topic_name[50];
    int msg_id;
    int client_id;
    int broker_id;
}master;

Any communication between Broker, Publisher and Subscriber is done using the above struct

• Setup (for network of 2 brokers)

1. Compile and run first_broker.c and enter the LISTEN_PORT.
2. Compile and run broker.c in another folder and input IP_ADDRESS and LISTEN_PORT of the first_broker as CLA, also assign LISTEN_PORT for the second broker.
3. Enter the IP_ADDRESS and LISTEN_PORT that you assigned to second broker in the first_broker.
4. Circular network of 2 broker has been established.
5. Compile and run publisher.c and enter the IP_ADDRESS and LISTEN_PORT of the any one of the brokers and follow the interface to publish a message.