• Server Sent Event or SSE is when a web page automatically gets updates from a server.
• A browser can subscribe to a stream of events generated by a server, receiving updates whenever a new event occurs.
• SSE is designed to use the JavaScript EventSource API in order to subscribe to a stream of data in any popular browser. Through this interface a client requests a particular URL in order to receive an event stream.

• This project is divided into two parts: backend and frontend.
• The backend utilizes express to create an event stream which EventSource of the browser can connect to.
• Whenever an update is generated by server, it will push it to every client connected and everybody receives the broadcasted message.
• The frontend part is a simple Next.js project with tailwind CSS for styling.
• So, when client is rendered in browser, it will connect with the server using EventSource and listens to onmessage event.
• Whenever a message is received, it will be shown in the UI.
• With the help of this, I have created a working prototype of a broadcasting chat application where, if clients are connected to the server, a client can broadcast the message to everyone.

NOTE 1: SSE is uni-directional, that is it sends data from server to client only. So, for sending the message from client to server, the post API endpoint is created. NOTE 2: SSE is used to send string data only, not binary data, so if some objects or arrays needed to passed, it has to use stringify and parse JSON, which is acceptable for small application with low updates, but it receives a performance hit when traffic is huge, both in data and clients or if the data is too complicated.

• SSE can be used to develop application which needs realtime data from server and just display it on client browser, like certain dashboards, text broadcaster, and many more things.

If the data seems to be very complicated, or data is in form of binary data, Web Sockets will be more viable option for that.