comet--Reverse Ajax (Basic knowledge)

Comet: server Push , as opposed to the AJAX page requesting data from the server. Data can be pushed to clients almost instantly.

But essentially the same: the browser initiates a request to the server, and the server responds to the request

Comet implementations: Long polling, HTTP streaming

1. Long polling-all browsers support

The browser sends a request to the server and responds if there is valid data on the server side, otherwise "ignores".

Once the server responds, the connection is closed and the browser sends the next request immediately.

2. HTTP stream-only some browsers natively support it

Sends a request only once during the life of the page, while the server keeps the connection open and periodically sends the data to the client

comet--Reverse Ajax (Basic knowledge)