Web server Wikipedia. A web server is a computer system that processes requests via HTTP, the basic network protocol used to distribute information on the World Wide Web. The term can refer to the entire system, or specifically to the software that accepts and supervises the HTTP requests. OvervieweditThe primary function of a web server is to store, process and deliver web pages to clients. The communication between client and server takes place using the Hypertext Transfer Protocol HTTP. Pages delivered are most frequently HTML documents, which may include images, style sheets and scripts in addition to text content. Philosophy Metaphilosophy Metaphysics Epistemology Ethics Politics Aesthetics Thought Mental Cognition. Bereich mit Programmen speziell fr Screen ReaderNutzer Hier finden Sie Freeware und DemoVersionen, die speziell fr Sehbehinderte und Blinde Screen Reader. The program uses various versions of Microsoft Speech API SAPI it allows to alter a voices parameters, including rate and pitch. The user can apply a special. UpdateStar is compatible with Windows platforms. UpdateStar has been tested to meet all of the technical requirements to be compatible with Windows 10, 8. Windows 8. Multiple web servers may be used for a high traffic website here, Dell servers are installed together being used for the Wikimedia Foundation. A user agent, commonly a web browser or web crawler, initiates communication by making a request for a specific resource using HTTP and the server responds with the content of that resource or an error message if unable to do so. The resource is typically a real file on the servers secondary storage, but this is not necessarily the case and depends on how the web server is implemented. While the primary function is to serve content, a full implementation of HTTP also includes ways of receiving content from clients. This feature is used for submitting web forms, including uploading of files. Many generic web servers also support server side scripting using Active Server Pages ASP, PHP, or other scripting languages. This means that the behaviour of the web server can be scripted in separate files, while the actual server software remains unchanged. Usually, this function is used to generate HTML documents dynamically on the fly as opposed to returning static documents. The former is primarily used for retrieving or modifying information from databases. Balabolka ist ein Programm zur Sprachausgabe oder TextToSpeech. The latter is typically much faster and more easily cached but cannot deliver dynamic content. Web servers are not only used for serving the World Wide Web. They can also be found embedded in devices such as printers, routers, webcams and serving only a local network. The web server may then be used as a part of a system for monitoring or administering the device in question. This usually means that no additional software has to be installed on the client computer, since only a web browser is required which now is included with most operating systems. Historyedit. The worlds first web server, a Ne. XT Computer workstation with Ethernet, 1. The case label reads This machine is a server. DO NOT POWER IT DOWNIn 1. Sir Tim Berners Lee proposed a new project to his employer CERN, with the goal of easing the exchange of information between scientists by using a hypertext system. The project resulted in Berners Lee writing two programs in 1. Between 1. 99. 1 and 1. World Wide Web helped to port them to many different operating systems and spread their use among scientific organizations and universities, and subsequently to industry. In 1. 99. 4 Berners Lee decided to constitute the World Wide Web Consortium W3. C to regulate the further development of the many technologies involved HTTP, HTML, etc. Path translationeditWeb servers are able to map the path component of a Uniform Resource Locator URL into A local file system resource for static requestsAn internal or external program name for dynamic requestsFor a static request the URL path specified by the client is relative to the web servers root directory. Consider the following URL as it would be requested by a client. The clients user agent will translate it into a connection to www. HTTP 1. 1 request. GET pathfile. html HTTP1. Host www. example. The web server on www. On an Apache server, this is commonly homewww on Unix machines, usually varwww. The result is the local file system resource. The web server then reads the file, if it exists, and sends a response to the clients web browser. The response will describe the content of the file and contain the file itself or an error message will return saying that the file does not exist or is unavailable. Kernel mode and user mode web serverseditA web server can be either incorporated into the OSkernel, or in user space like other regular applications. Web servers that run in user mode have to ask the system for permission to use more memory or more CPU resources. Not only do these requests to the kernel take time, but they are not always satisfied because the system reserves resources for its own usage and has the responsibility to share hardware resources with all the other running applications. Executing in user mode can also mean useless buffer copies which are another handicap for user mode web servers. Load limitseditA web server program has defined load limits, because it can handle only a limited number of concurrent client connections usually between 2 and 8. IP address and TCP port and it can serve only a certain maximum number of requests per second RPS, also known as queries per second or QPS depending on its own settings,the HTTP request type,whether the content is static or dynamic,whether the content is cached, andthe hardware and software limitations of the OS of the computer on which the web server runs. When a web server is near to or over its limit, it becomes unresponsive. Causes of overloadeditAt any time web servers can be overloaded due to Excess legitimate web traffic. Thousands or even millions of clients connecting to the web site in a short interval, e. Slashdot effect Distributed Denial of Service attacks. A denial of service attack Do. S attack or distributed denial of service attack DDo. S attack is an attempt to make a computer or network resource unavailable to its intended users Computer worms that sometimes cause abnormal traffic because of millions of infected computers not coordinated among themXSS viruses can cause high traffic because of millions of infected browsers or web servers Internet bots Traffic not filteredlimited on large web sites with very few resources bandwidth, etc. Internet network slowdowns, so that client requests are served more slowly and the number of connections increases so much that server limits are reached Web servers computers partial unavailability. This can happen because of required or urgent maintenance or upgrade, hardware or software failures, back end e. Symptoms of overloadeditThe symptoms of an overloaded web server are Requests are served with possibly long delays from 1 second to a few hundred seconds. The web server returns an HTTP error code, such as 5. The web server refuses or resets interrupts TCP connections before it returns any content. In very rare cases, the web server returns only a part of the requested content. Garmin Topo Czech 2010. This behavior can be considered a bug, even if it usually arises as a symptom of overload. Anti overload techniqueseditTo partially overcome above average load limits and to prevent overload, most popular web sites use common techniques like Managing network traffic, by using. Firewalls to block unwanted traffic coming from bad IP sources or having bad patterns. HTTP traffic managers to drop, redirect or rewrite requests having bad HTTP patterns. Bandwidth management and traffic shaping, in order to smooth down peaks in network usage. Deploying web cache techniques. Using different domain names to serve different static and dynamic content by separate web servers, e.