Long polling and short polling differences

Long polling and short polling are techniques used in web development to implement real-time data updates from a server to a client, such as in chat applications, live news feeds, or any scenario where data needs to be updated dynamically. Both methods are strategies to allow clients (web browsers, mobile apps, etc.) to "poll" or check for updates from the server at regular intervals or under certain conditions. However, they operate differently and have their own advantages and disadvantages depending on the use case.

Short Polling

Short polling is the more straightforward approach of the two. In short polling, the client repeatedly requests (or polls) the server at fixed intervals to check for any new updates. If there are updates, the server responds with the new data; if not, it responds with an empty response or a signal indicating that there is no new data.

How Short Polling Works:

1. Client Request: The client sends a request to the server asking for new information.
2. Server Response: The server immediately checks for new data. If new data is available, it sends it back to the client. If there is no new data, it sends a response indicating that there is no new information.
3. Wait and Repeat: The client waits for a predetermined period and then sends another request, repeating the process.

Advantages:

• Simple to implement.
• Works well for applications where real-time updates are not critical.

Disadvantages:

• Inefficient use of resources, as it involves sending repetitive requests to the server, which can lead to unnecessary network traffic and server load.
• Not truly real-time, as updates are only received after the client sends a new request following the interval.

Long Polling

Long polling is a technique designed to reduce the inefficiencies of short polling by keeping a request open until the server has new data to send to the client. Instead of sending back an immediate empty response when there is no new data, the server holds the request and responds as soon as new data becomes available (or after a timeout period).

How Long Polling Works:

1. Client Request: The client sends a request to the server just like in short polling.
2. Server Hold: Instead of responding immediately, the server holds the request open.
3. Server Response: When new data becomes available, the server sends the response back to the client with the new data. If a timeout occurs without new data, the server sends an empty response.
4. New Request: After receiving a response (data or timeout), the client immediately sends another request, and the process repeats.

Advantages:

• More efficient than short polling for real-time applications, as it reduces the number of unnecessary requests.
• Provides a quicker response to updates, as the server sends data as soon as it's available.

Disadvantages:

• Can be more complex to implement and manage due to the need to handle hanging requests.
• Holding connections open can increase server load, especially if many clients are connected simultaneously.

Final Thoughts

Choosing between short polling and long polling depends on the specific requirements of your application, such as how real-time the updates need to be and the expected server load. While both strategies aim to achieve real-time communication between the client and server, long polling is generally more efficient and provides a quicker response to changes. However, it also requires careful consideration of server resource management. In modern web development, other techniques like WebSockets or server-sent events (SSE) are also commonly used for real-time communication, offering advantages over both short and long polling in suitable scenarios.