Describe the difference between WebSocket and SSE, and use cases for each.

WebSocket and Server-Sent Events (SSE) are technologies for real-time data transfer from server to client, but they have fundamental differences.

WebSocket:

• A full-duplex communication channel between client and server.
• Allows both server and client to send data at any time.
• Used for interactive applications where fast and bidirectional communication is important (chats, games, trading platforms).
• Requires establishing a connection using a special protocol (ws:// or wss://).

SSE (Server-Sent Events):

• A unidirectional channel: the server can send data to the client, but the client cannot send data through this channel.
• Uses standard HTTP protocol with support for the EventSource API in browsers.
• Well-suited for real-time updates where the client only listens to the server (news feeds, notifications, monitoring).
• Simpler to implement and scale than WebSocket.

Use cases:

• WebSocket: chat applications, online games, real-time collaboration.
• SSE: news feeds, status updates, notifications, where the client does not send data to the server.

In Go, the gorilla/websocket library is often used for WebSocket, and for SSE, you can simply write to http.ResponseWriter with the correct headers and keep the connection open.