In computer science the term Polling refers to actively sampling the status of an external device by a client program as a synchronous activity.

An example of polling can be found in many online chat solutions where a server must queue messages and wait to be asked by a client. This is the most common mechanism for chat utilizing the Ajax (programming) web communications technique. Asynchronous JavaScript And XML, or its acronym, Ajax (Pronounced Ah-yahx), is a Web development technique for creating interactive web applications. ...