Jakarta WebSocket enables two-way communication between client and server endpoints. First, each client makes an HTTP connection to a Jakarta WebSocket server. The server can then broadcast messages to the clients. Server-Sent Events (SSE) also enables a client to receive automatic updates from a server via an HTTP connection however WebSocket differs from Server-Sent Events in that SSE is unidirectional from server to client, whereas WebSocket is bidirectional. WebSocket also enables real-time updates over a smaller bandwidth than SSE. The connection isn’t closed meaning that the client can continue to send and receive messages with the server, without having to poll the server to receive any replies.

You’ll learn how to use the Jakarta WebSocket API to build the system service and the scheduler in the client service. The scheduler pushes messages to the system service every 10 seconds, then the system service broadcasts the messages to any connected clients. You will also learn how to use a JavaScript WebSocket object in an HTML file to build a WebSocket connection, subscribe to different events, and display the broadcasting messages from the system service in a table.