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The module <HTTP> of subsystem "Protocols"

Module: HTTP
Name: HTTP-realization
Type: Protocol
Version: 3.1
Author: Roman Savochenko, Maxim Lysenko (2009)
Description: Provides support for the HTTP protocol for WWW-based user interfaces.
License: GPL



Module of the transport protocol HTTP is designed to support the implementation of network protocol HTTP (Hypertext Transfer Protocol) in the system OpenSCADA.

HTTP Protocol is used to transfer the WWW contents. For example, via HTTP the following types of documents are transmitted: html, xhtml, png, java, and many others. Adding the HTTP support in OpenSCADA system together with the Sockets transport allows to implement various user functions based on the WWW interface. The module implements two main methods of the HTTP protocol: "GET" and "POST". "HTTP" module provides control of the integrity of HTTP-queries and, jointly with "Sockets" transport, allows to "collect" holistic requests of their fragments, as well as maintain the keeping of the connection alive (Keep-Alive).

For flexible connection of the user interfaces to the module the modular mechanism within the module HTTP is used. In the role of modules the modules of subsystem the "User interfaces" are used with the additional information field "SubType" with the value of "WWW".

In the requests for the Web resources the URL(Universal Resource Locator) are commonly used, hence the URL is passed as the main parameter via HTTP. The first element of the requested URL is used to identify the module UI. For example URL "http://localhost:10002/WebCfg" means address to module WebCfg on the host "http://localhost:10002". In the case of an incorrect indication of the module ID, or when you address without identifier of the module at all, HTTP module generates the dialogue of the information on the input and with the choice of one of the available user interfaces. Example of a dialogue is shown in Figure 1.

Dialog of the choice of WWW-interface module. (39 )
Fig.1. Dialog of the choice of WWW-interface module.

The module supports multi-language which one enabled by the dynamic messages translation of OpenSCADA.

A language of the end-user interface detects in way and by order:

Gotten in the way language used for interfaces of the module building and passes to WWW sub-modules into HTTP property "oscd_lang" of the argument "vars" of the "GET" and "POST" functions.

To configure and control of the module there allowed a configuration page of the control interface of OpenSCADA (Fig.3) where you can:

The module configuring page. (83 )
Fig.3. The module configuring page.

1. Authentication

Module supports authentication in the system OpenSCADA while providing access to the WEB-interface modules (Fig.2).

Authentication dialogue in the system OpenSCADA. (11 )
Fig.2. Authentication dialogue in the system OpenSCADA.

For ease of working with Web-based interfaces the module provides an ability to automatically log on from name of the specified user. Configuring for the automatic login makes by the module settings page (Fig.3). Automatic login performs by matching the address indicated in the column "Address", on behalf of the user specified in the column "User".

For more security you can set only Web users into the list of users allowed for authentication.

2. Modules of the user WEB-interface

Modules of the user interface (UI) designed to work with HTTP module, should indicate an information field "SubType" with the value "WWW" and "Auth" field with the value "1" if the module requires an authentication at login. For communication of HTTP module and UI modules an advanced communication mechanism is used. This mechanism involves the export of interface functions. In this case the UI modules must export the following function:

void HttpGet( const string &url, string &page, const string &sender, vector<string> &vars, const string &user ); GET method with the parameters:
url address of the request;
page page with the answer;
sender address of the sender;
vars request variables;
user user of the system;
iprt pointer to an input part object of the protocol.

void HttpPost( const string &url, string &page, const string &sender, vector<string> &vars, const string &user ); POST method with the parameters:
url address of the request;
page page with the answer and with the contents of the body of the POST request;
sender address of the sender;
vars request variables;
user user of the system;
iprt pointer to an input part object of the protocol.

Then, in the case of a HTTP GET request, the function HTTP_GET or HttpGet will be called, and in the case of the POST request, the function HTTP_POST or HttpPost will be called in the appropriate UI module.

3. Outgoing requests function's API

The outgoing function (messIO()) of API operate by HTTP-request's content which wrapped to XML-packages. The request structure is:

<req Host="host" URI="uri">
  <prm id="pId">pVal</prm>
  <cnt name="cName" filename="cFileName">
    <prm id="cpId">cpVal</prm>


Request result's structure is:

<req Host="host" URI="uri" err="err" Protocol="prt" RezCod="rCod" RezStr="rStr">
  <prm id="pId">pVal</prm>


Into example role we accord using the function into users procedures for GET and POST requests making by language JavaLikeCalc.JavaScript:

//GET request for HTML-page
req = SYS.XMLNode("GET");
test = req.text();

//GET request for file
req = SYS.XMLNode("GET");
if(!req.attr("err").length) SYS.fileWrite("/var/tmp/recvFile.tmp", req.text());

//POST request
req = SYS.XMLNode("POST");
cntNode = req.childAdd("cnt").setAttr("name","pole0").setAttr("filename","Object2-k001-100309-17.txt");
cntText = "Object2-k001\r\n";
cntText += "\r\n";
cntText += "v002\r\n";
cntText += " n1\r\n";
cntText += "  09.03.10 16   Polnyj    7155.25    216.0  32.000  17.5\r\n";
cntText += "v005\r\n";
cntText += " n1\r\n";
cntText += "  09.03.10 16   Polnyj     188.81    350.0   4.000  40.0\r\n";
cntText += "\r\n";

4. User programming API

The same module's object "Protocol.HTTP" [SYS.Protocol.HTTP.pgCreator()]


Referring pages: HomePageEn/Doc

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