What are Server-Sent Events (SSE)?

In the context of development environments, the need for real-time data streaming is a common occurrence. Two of the most widely used technologies to support this requirement are Server-Sent Events (SSE) and WebSocket. Server-Sent Events (SSE) is a broadcasting model based on the HTTP/1.1 protocol that enables servers to continuously send data to browsers. This technology allows for event-driven communication between the server and the client, where the server can send notifications and updates to the client as they occur, without the need for the client to actively request them. This is particularly useful in scenarios where the server needs to push updates or notifications to the client in real-time, such as in live updates, live streaming, or real-time reporting. In an SSE connection, the server continuously sends data to the client through a unidirectional stream, which is open until the client explicitly indicates that it wants to close the connection. The server sends events to the client by sending HTTP responses with a special type of HTTP response header, event-stream or text/event-stream, which indicates that the response is a stream of events. Each event is represented by a pair of headers, one for the event data and another for any additional metadata. Using SSE allows developers to build real-time applications and services that can push updates and notifications to clients in an efficient, scalable, and reliable manner.