In blogging, ping is an XML-RPC-based push mechanism by which a weblog notifies a server that its content has been updated. An XML-RPC signal is sent to one or more "ping servers,"[clarification needed] which can then generate a list of blogs that have new material. The technology was first introduced by Dave Winer to Weblogs.com in October 2001. Today, most blog authoring tools automatically ping one or more servers each time the blogger creates a new post or updates an old one.
Open ping servers, like Moreover Technologies' Weblogs.com, let other web services subscribe to a list of blogs that have recently pinged them. Blog search engines can provide fresh results very quickly by polling only the newly-updated blogs. Similarly, aggregators use results from ping servers to tell subscribers which items on their subscription lists have fresh material.
In addition to open ping servers, there are also proprietary ping servers that gather information only for their own applications. Most of the major blog search engines operate such ping servers.
Unlike open ping servers, proprietary servers with their own subscription applications have no incentive to share their received ping data directly with other servers, which may offer competing services. As these servers do not share their data, bloggers have to ping a large number of individual servers to receive the desired publicity. As a result, bloggers have turned to services such as Ping-o-Matic!, Pingler.com and Index Me™, which ping multiple proprietary ping servers and remove the need for website owners to acquire new servers to ping themselves.
Ping spam 
The use of ping servers to direct attention to recent blog posts has led to a rash of ping spam or sping, which attempts to direct readers to web pages that are not, in fact, recent blog posts. Examples:
- Product vendors who use a weblog-like format to post product ads, meaningless batches of Google keywords, etc.
- Software vendors, who sell scripts that make automated "weblog postings" every hour around the clock.
Creators of ping spam or spam blogs may hope to benefit by creating pages to turn up in web searches for popular keywords. Typically, an individual spam post links to some external page that displays Google ads or offers a product for sale.
See also 
- Pingback, a variant of trackbacks based on the ping notification mechanism
- RSS and Atom, the main syndication formats used for blogs
- Original announcement of blog pinging by Dave Winer, September 30, 2001
- Ping, Ping, Ping… the Spiders Crawling… by Dahlia Lamy, December 20, 2012