Package: inet.applications.httptools.server

HttpServer

simple module

A Web server module for OMNeT++ simulations. This module is intended for use with the INET StandardHost module and plugs in as a tcpApp. The INET TCP/IP stack modeling is used for transport. See the INET documentation for more details.

The purpose of the HTTPServer component is to simulate a Web server operating on a single host. It operates in conjunction with the browser component to provide a realistic simulation of Web usage patterns.

The activity of the server is characterized by the requests it receives. It responds to requests by serving documents or resources.

A server receives a HTTP page request from a browser. If the browsers message is marked as bad, the server will respond with a 404:Not found message. Otherwise, the server will respond with a 200:OK HTML response. The body of the response is a list of resource references, as further described in HTTPMessage. The receiving browser is expected to issue requests for those resources, as discussed in HTTPBrowser. A server in responds to each resource request with a message consistent with the object requested. The size of the HTML page or resource sent is solely determined by the server receiving the corresponding request.

The component has two modes of operation:

Random document generation mode, in which the server responds to requests for HTML documents by generating replies according to statistical distributions.
Scripted mode, in which the pages and resources served are predetermined.

Random document generation mode

The goal for this mode of operation is for the server component to exhibit traffic patterns, which are statistically similar to ones derived from measurements of real systems. The component is initialized with a number of parameters, shown in table below, which define its behavior. The parameters are defined in a XML file and can be determined at run time by various random distributions, as was discussed for the browser component.

Parameters:

pageSize: The size of the generated HTML document
numResources: The number of referenced resources per HTML page
textImageResourceRatio: The ratio of images to text resources on HTML pages
imageResourceSize: The size of image resources
textResourceSize: The size of text resources, e.g. CSS documents
replyDelay: The delay in processing of each received HTML request before sending reply

In this mode, the server responds to a HTML page request by assembling a response containing a random number of resources. The number of resource references and their type is determined by random distributions, according to the initialization parameters. Similarly, requests for resources are answered by messages of a size consistent with the size distributions for the object in question.

Every server in a simulation can be configured with different parameters, although this would quickly become unwieldy in a large simulation. The flexibility to define groups or categories of servers will however prove useful in many cases.

Scripted mode

Repeatable response by a subset of servers in a simulation can be useful in a variety of situations, e.g. for testing purposes. This is provided by the scripted server mode. A Web site is defined in some detail using a site definition file. The definition file is specified by setting a scriptFile initialization parameter. The file format is:

[HTML]
[path/]{name}[.extension];{definition file}
[RESOURCES]
[path/]{name.extension};{size}

The HTML section lists the hosted HTML pages and their associated definition files, one for each hosted HTML page. The page definition file is normally named {U\R\L}.def (the resource URL string, with~ replaced by), although any name can certainly be used. The format of the page definition file is the same as used for the generated HTML message body, a simple list of the referenced resources. A optional entry with URL as default can be used to specify a default page for the site, e.g. an error page.

The RESOURCES section lists all resources available for the site, their type (image or text) and size in bytes.

The server responds with a message containing the specified page or resource if the request can be satisfied (a 200:OK reply). Otherwise, a 404:Not found reply is issued.

See also: HttpServerDirect

See also: DirectHost

Author: Kristjan V. Jonsson

Inheritance diagram

The following diagram shows inheritance relationships for this type. Unresolved types are missing from the diagram.

Parameters

Name	Type	Default value	Description
hostName	string	""	The domain name of the server
port	int	80	The listening port number
httpProtocol	int	11	The http protocol: 10 for http/1.0, 11 for http/1.1. Not used at the present time.
logFile	string	""	Name of server log file. Events are appended, allowing sharing of file for multiple servers.
siteDefinition	string	""	The site script file. Blank to disable.
activationTime	double	0s	The initial activation delay. Zero to disable.
config	xml		The XML configuration file for random sites

Gates

Name	Direction	Size	Description
tcpIn	input
tcpOut	output

Source code

//
// A Web server module for OMNeT++ simulations. This module is intended for use with the
// INET StandardHost module and plugs in as a tcpApp. The INET TCP/IP stack modeling is
// used for transport. See the INET documentation for more details.
//
// The purpose of the HTTPServer component is to simulate a Web server operating on a single host.
// It operates in conjunction with the browser component to provide a realistic simulation of Web
// usage patterns.
//
// The activity of the server is characterized by the requests it receives. It responds to requests
// by serving documents or resources.
//
// A server receives a HTTP page request from a browser. If the browsers message is marked as bad,
// the server will respond with a 404:Not found message. Otherwise, the server will respond with
// a 200:OK HTML response. The body of the response is a list of resource references, as further
// described in HTTPMessage. The receiving browser is expected to issue requests for those
// resources, as discussed in HTTPBrowser. A server in responds to each resource request with a
// message consistent with the object requested. The size of the HTML page or resource sent is
// solely determined by the server receiving the corresponding request.
//
// The component has two modes of operation:
//
// - Random document generation mode, in which the server responds to requests for HTML documents
// by generating replies according to statistical distributions.
// - Scripted mode, in which the pages and resources served are predetermined.
//
// <h1>Random document generation mode</h1>
//
// The goal for this mode of operation is for the server component to exhibit traffic patterns,
// which are statistically similar to ones derived from measurements of real systems. The component
// is initialized with a number of parameters, shown in table below, which define its behavior.
// The parameters are defined in a XML file and can be determined at run time by various random
// distributions, as was discussed for the browser component.
//
// Parameters:
// - pageSize: The size of the generated HTML document
// - numResources: The number of referenced resources per HTML page
// - textImageResourceRatio: The ratio of images to text resources on HTML pages
// - imageResourceSize: The size of image resources
// - textResourceSize: The size of text resources, e.g. CSS documents
// - replyDelay: The delay in processing of each received HTML request before sending reply
//
// In this mode, the server responds to a HTML page request by assembling a response containing
// a random number of resources. The number of resource references and their type is determined
// by random distributions, according to the initialization parameters. Similarly, requests for
// resources are answered by messages of a size consistent with the size distributions for the
// object in question.
//
// Every server in a simulation can be configured with different parameters, although this would
// quickly become unwieldy in a large simulation. The flexibility to define groups or categories
// of servers will however prove useful in many cases.
//
// <h1>Scripted mode</h1>
//
// Repeatable response by a subset of servers in a simulation can be useful in a variety of
// situations, e.g. for testing purposes. This is provided by the scripted server mode. A Web
// site is defined in some detail using a site definition file. The definition file is specified
// by setting a scriptFile initialization parameter. The file format is:
//
// <pre>[HTML]
// [path/]{name}[.extension];{definition file}
// [RESOURCES]
// [path/]{name.extension};{size}</pre>
//
// The HTML section lists the hosted HTML pages and their associated definition files, one for
// each hosted HTML page. The page definition file is normally named {U\R\L}.def (the resource
// URL string, with~ replaced by), although any name can certainly be used. The format of the
// page definition file is the same as used for the generated HTML message body, a simple list
// of the referenced resources. A optional entry with URL as default can be used to specify a
// default page for the site, e.g. an error page.
//
// The RESOURCES section lists all resources available for the site, their type (image or text)
// and size in bytes.
//
// The server responds with a message containing the specified page or resource if the request
// can be satisfied (a 200:OK reply). Otherwise, a 404:Not found reply is issued.
//
// @see HttpServerDirect
// @see DirectHost
//
// @author Kristjan V. Jonsson
//
simple HttpServer like ITCPApp
{
parameters:
string hostName = default(""); // The domain name of the server
int port = default(80); // The listening port number
int httpProtocol = default(11); // The http protocol: 10 for http/1.0, 11 for http/1.1. Not used at the present time.
string logFile = default(""); // Name of server log file. Events are appended, allowing sharing of file for multiple servers.
string siteDefinition = default(""); // The site script file. Blank to disable.
double activationTime @unit("s") = default(0s); // The initial activation delay. Zero to disable.
xml config; // The XML configuration file for random sites
gates:
input tcpIn;
output tcpOut;
}

File: src/inet/applications/httptools/server/HttpServer.ned