WebSockets SSE and Long Polling

WebSocket

• Implemented by WebSocket class
• Bidirectional: both client and server exchange the messages
• Data: Binary and Text Data
• Protocol: WebSocket:
  • ws://
  • wss:// (with TLS) - Similar to https://
• First the handshake is done by client request and server response
• Then connection is upgraded from http:// to ws:// protocol
• WebSocket class:
  • Methods:
    • socket.send(data)
    • socket.close([code], [reason])
  • Events:
    • open
    • message
    • error
    • close

Server Sent Events (SSE)

• Implemented by EventSource class
• Unidirectional: Server sends the data
• Data: Only Text Data
• Protocol: HTTP
• Simple to implement compared to WebSockets
• EventSource class:
  • Properties:
    • readyState:
      • EventSource.CONNECTING (0)
      • EventSource.OPEN (1)
      • EventSource.CLOSED (2)
    • lastEventId
  • Methods:
    • close()
  • Events:
    • open
    • message
    • error
• Spring boot SSE implementation: https://www.baeldung.com/spring-server-sent-events

Long Polling