Pull technology or client pull is a style of network communication where the initial request for data originates from the client, and then is responded to by the server. The reverse is known as push technology

Push technology

Push technology, or server push, describes a style of Internet-based communication where the request for a given transaction is initiated by the publisher or central server...

, where the server pushes data to clients.. Usually, customers will look for a site and visit only if it provides helpful and attractive contents and display. The pull technology is effective and economical when advertising to open, unidentified potential customers world wide. It is more effective for the customer when he searches for a specific item.

Pull requests form the foundation of network computing, where many clients request data from centralised servers. Pull is used extensively on the Internet

Internet

The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...

 for HTTP page requests from websites.

A push can also be simulated using multiple pulls within a short amount of time. For example, when pulling POP3 email messages from a server, a client can make regular pull requests every few minutes. To the user, the email then appears to be pushed, as emails appear to arrive close to real-time. The tradeoff is this places a heavier load on both the server and network in order to function correctly.

Most web feeds, such as RSS

RSS (file format)

RSS is a family of web feed formats used to publish frequently updated works—such as blog entries, news headlines, audio, and video—in a standardized format...

 are technically pulled by the client. With RSS, the user's RSS reader polls the server periodically for new content; the server does not send information to the client unrequested. This continual polling is inefficient and has contributed to the shutdown or reduction of several popular RSS feeds that could not handle the bandwidth. For solving this problem, the PubSubHubbub protocol as another example of a push technology was devised.

See also

• Client–server model
• File transfer
  File transfer
  File transfer is a generic term for the act of transmitting files over a computer network or the Internet. There are numerous ways and protocols to transfer files over a network. Computers which provide a file transfer service are often called file servers. Depending on the client's perspective the...
  
  
• Push technology
  Push technology
  Push technology, or server push, describes a style of Internet-based communication where the request for a given transaction is initiated by the publisher or central server...
  
  
• Push email
• Lazy evaluation
  Lazy evaluation
  In programming language theory, lazy evaluation or call-by-need is an evaluation strategy which delays the evaluation of an expression until the value of this is actually required and which also avoids repeated evaluations...