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Long Polling vs WebSockets

Both long polling and WebSockets are techniques used for real-time, bi-directional communication between a client and a server. Understanding their differences is key in selecting the right approach for real-time web applications.

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Long Polling​

Overview​

  • Long Polling is an advanced form of the traditional polling method, where the server holds a client's request open until it has new data to send.
  • The connection is closed once the data is sent, and the client immediately establishes a new connection.

Key Features​

  • Hold and Respond: Holds the client request until data is available.
  • HTTP-Based: Operates over standard HTTP protocols.
  • Server-Initiated Response: Server sends data as it becomes available.

Use Cases​

  • Chat Applications: Useful for less active chat applications.
  • Live Event Updates: Suitable for events with less frequent updates.

WebSockets​

Overview​

  • WebSockets provide a full-duplex communication channel over a single, long-lived connection established between the client and server.
  • This connection allows for real-time, bidirectional data transfer.

Key Features​

  • Persistent Connection: Maintains a continuous connection between client and server.
  • Low Latency: Ideal for applications that require minimal delay.
  • Full Duplex: Enables simultaneous two-way communication.

Use Cases​

  • High-Volume Chat Applications: Ideal for active, real-time user interactions.
  • Live Streaming: Efficient for streaming data in real-time.
  • Interactive Games: Crucial for real-time multiplayer gaming experiences.

Key Differences​

  1. Connection Type: Long polling uses a series of intermittent HTTP requests, while WebSockets establish a persistent, full-duplex connection.
  2. Latency: WebSockets generally offer lower latency compared to long polling.
  3. Protocol: Long polling is based on HTTP, whereas WebSockets use their own protocol (ws:// or wss://).
  4. Data Transfer: WebSockets allow for more efficient data transfer with less overhead.
  5. Complexity and Support: WebSockets can be more complex to implement and require specific server-side support.

In summary, WebSockets are generally more efficient and suitable for high-demand, real-time applications, while long polling may be preferred in scenarios where WebSocket support is not available or for applications with less frequent update requirements.