What is reverse Ajax?

The basic concept of reverse Ajax is that the client does not have to obtain information from the server, and the server directly pushes the information to the client. The purpose of this solution is to solve a limitation imposed by the traditional Ajax web model: real-time information is difficult to solve technically. The reason is that the client must contact the server and take the initiative to ask if there is a change. If there is a change, the page (or part of the page) will be updated ). Although this operation can be completed very quickly, it seems to be real-time, but it is not actually real-time. What we need is to contact the server to view all the browsers on its page and notify them of the changes.