Push technology

Push notifications are small messages that can reach audiences anywhere and anytime. While pop-ups appear only when audiences are on the site they belong to, push messages are independent of sites. They are associated with web browsers and apps. Push notifications are small messages that can reach audiences anywhere and anytime. While pop-ups appear only when audiences are on the site they belong to, push messages are independent of sites. They are associated with web browsers and apps. Push technology, or server push, is a style of Internet-based communication where the request for a given transaction is initiated by the publisher or central server. It is contrasted with pull/get, where the request for the transmission of information is initiated by the receiver or client. Push services are often based on information preferences expressed in advance. This is called a publish/subscribe model. A client 'subscribes' to various information 'channels' provided by a server; whenever new content is available on one of those channels, the server pushes that information out to the client. Push is sometimes emulated with a polling technique, particularly under circumstances where a real push is not possible, such as sites with security policies that require rejection of incoming HTTP/S requests. Synchronous conferencing and instant messaging are typical examples of push services. Chat messages and sometimes files are pushed to the user as soon as they are received by the messaging service. Both decentralised peer-to-peer programs (such as WASTE) and centralised programs (such as IRC or XMPP) allow pushing files, which means the sender initiates the data transfer rather than the recipient. Email may also be a push system: SMTP is a push protocol (see Push e-mail). However, the last step—from mail server to desktop computer—typically uses a pull protocol like POP3 or IMAP. Modern e-mail clients make this step seem instantaneous by repeatedly polling the mail server, frequently checking it for new mail. The IMAP protocol includes the IDLE command, which allows the server to tell the client when new messages arrive. The original BlackBerry was the first popular example of push-email in a wireless context. Another example is the PointCast Network, which was widely adopted in the 1990s. It delivered news and stock market data as a screensaver. Both Netscape and Microsoft integrated push technology through the Channel Definition Format (CDF) into their software at the height of the browser wars, but it was never very popular. CDF faded away and was removed from the browsers of the time, replaced in the 2000s with RSS (a pull system.) Other uses of push-enabled web applications include software updates distribution ('push updates'), market data distribution (stock tickers), online chat/messaging systems (webchat), auctions, online betting and gaming, sport results, monitoring consoles, and sensor network monitoring. The Webpush proposal of the Internet Engineering Task Force is a simple protocol using HTTP version 2 to deliver realtime events, such as incoming calls or messages, which can be delivered (or “pushed”) in a timely fashion. The protocol consolidates all real-time events into a single session which ensures more efficient use of network and radio resources. A single service consolidates all events, distributing those events to applications as they arrive. This requires just one session, avoiding duplicated overhead costs.