HTTP server push

HTTP server push (also known as HTTP streaming) is a mechanism for sending data from a web server to a web browser. HTTP server push can be achieved through several mechanisms.

Generally the web server does not terminate a connection after response data has been served to a client. The web server leaves the connection open such that if an event is received, it can immediately be sent to one or multiple clients. Otherwise the data would have to be queued until the client's next request is received. Most web servers offer this functionality via CGI (e.g. NPH scripts on Apache).

Another mechanism is related to a special MIME type called multipart/x-mixed-replace, which was introduced by Netscape in 1995. Web browsers would interpret this as a document changing whenever the server felt like pushing a new version to the client.^[1][2] It is still supported by Firefox, Opera and Safari today, but traditionally ignored by Microsoft.^[3] It can be applied to HTML documents, but also for streaming images in webcam applications.

The WHATWG Web Applications 1.0 proposal^[4] included a mechanism to push content to the client. On September 1, 2006, the Opera web browser implemented this new experimental technology in a feature called "Server-Sent Events."^[5][6] It is now being standardized as part of HTML5.^[7] Another related part of HTML5 is the Web Sockets API, which allows a web server and client to communicate over a full-duplex TCP connection.^[8] Web Sockets are available on Google Chrome since 4.0.249.0^[9], and there is a JavaScript library by Kaazing that emulates them