2. Two-way data communication methods

• Like most things, there are a few ways to go about achieving two-way data communication
• They each have their pros and cons, and some are more popular than others

1. Polling

• How it Works:
  • The client sends repeated HTTP GET requests to the server, usually at some fixed rate to check for updates
  • This is essentially the equivalent of just refreshing the page periodically to see if things have updated
• Advantages:
  • Simple to implement and requires no specialized server setup, it uses the exact same setup as sending other network request
  • Compatible with most browsers and server configurations.
• Disadvantages:
  • Inefficient as it has to send the requests constantly, even if there’s no new data to fetch as there’s no way of knowing there’s no new data
  • Adds latency between updates due to the fixed interval
  • Increases server load due to frequent requests, you could almost DoS your server if you weren’t careful
• Use Cases:
  • Applications where real-time updates are not critical (e.g., checking email or news feed)

2. Long Polling

• How it Works:
  • Similar to polling, the client sends a request to the server. However, this time the server holds the connection open until new data is available.
  • Once the server responds, the client immediately sends another request to repeat the cycle
  • This means fewer requests, but those requests that get sent take longer to handle
• Advantages:
  • Reduces the number of unnecessary requests compared to traditional polling
  • Provides updates closer to real-time as the request automatically returns whenever new data is available
• Disadvantages:
  • Still has some overhead from repeated requests.
  • Can be difficult to scale for a high traffic application
• Use Cases:
  • Chat systems or lightweight real-time applications where WebSockets are unavailable.

3. Server-Sent Events (SSE)

• How it Works:
  • The server pushes updates to the client over a single persistent connection (usually HTTP)
  • Only supports one-way communication from server to client
  • Usually you would use this in conjunction with regular POST or PUT requests to send data to the server
• Advantages:
  • Simple protocol; uses native browser support with EventSource API
  • Efficient for server-to-client updates
• Disadvantages:
  • Limited to one-way communication
  • Only works over HTTP or HTTPS, not suitable for certain bidirectional use cases
  • May not work in environments requiring two-way communication
• Use Cases:
  • Stock price updates, live scores, or notifications.

4. WebSockets

• How it Works:
  • Establishes a persistent, full-duplex communication channel between client and server
  • Both client and server can send messages at any time without additional HTTP requests
  • Doesn’t use HTTP, but rather it’s own protocol over a single TCP connection (socket)
• Advantages:
  • Real-time, low-latency communication
  • Efficient use of resources, as it avoids repeated request-response cycles
  • Supports bi-directional data flow natively
• Disadvantages:
  • Requires specialized server and client setup
  • Not supported in older browsers (however modern browser support is standard)
• Use Cases:
  • Live chat systems, multiplayer games, collaborative tools (e.g., Google Docs), IoT applications.

Comparison Table