DATA ACQUISITION AND TRANSFER TROUGHT INTERNET

Lecturer Turc Traian PhD

“Peru Maior” University of Targu Mures

Abstract: General data from different systems can be achieved and sent to a large number of users, in WEB pages format The WEB server collects data and generates the WEB page in a standard format or in a client request format.

Data are acquisitioned using a data acquisition server that is in charge also with data transfer through Internet. The server is both data acquisition server and WEB server. The purpose of the WEB server is preparing data in HTML format or DBF format and then using MIIS to send data at client’s request.

Keywords: web, server, data acquisition, client server, request.

  1. WEB SERVER FOR DATA ACQUISITION AND DATA TRANSFER

For sending acquisitioned data for long distance to a large number of users at low costs it is better to use the public network Internet.

Using this network means a major advantage: the possibility of displaying data using any computer connected to the Internet using any kind of Internet browser.

The users don’t need expansive and sophisticated programs for data acquisition and data displaying. (See figure 1)

Figure1

Data transfer and display can be done using different methods. A simple way is using data files in HTML (Hyper Text Mark up Language), format using in documents transfer through Internet (see figure 2).

Figure 2

The local computer connected to the data acquisition system, takes data and after data processing makes data display. Acquisitioned data are saved in different format from time to time to the local disks for future using.

For data transfer there is generated another special file in HTML format with acquisitioned data and even data brief from the last period. The program, which prepares data in HTML file, is called SERVER HTML application.

The WEB server performs the HTML file transfer at client’s URL request.

Users can display data to the local computer connected to the Internet using any available Internet browser simply addressing server that contains the HTML file with acquisitioned data.

The Internet address contains the URL (Universal Resource Locator) of the resource, in other words the name of server and the name oh HTML document.

The content of resource is permanently changing. Any display of this resource means display of new data.

The HTML file generated by the HTML server can contain data and other TAG-s that allow users to request specific data.

If the browser displays repetitively the HTML file we have a real time displaying.

The method described before is very simple, the data access is very fast, the users number simultaneously connected depend only on WEB server performances.

The users don’t access directly the acquisition server and they can’t brake down the data acquisition by a large number of requesting.

The disadvantage of this method: the users can’t make a particularly request, they can only display data prepared by HTML server.

To solve this problem there must be used a client server application when the client makes some request and the server provides only requested data (see figure 3)

Figure 3

Using Internet browser one can display data from server by invoking server address and specific data request (URL). Specific data request includes the name of the script, the process (the application) that must be launched and the method that sends necessary data.

The Internet browser asks for this address (URL) like any other document from server. The server receives the request, understands the fact that URL is a script and runs the script. The script launches the process and invokes the method received in URL.

The method can get data from databases or can make a data acquisition. The data are sent to script in HTML format. The script sends a valid response for the server.

The WEB server sends the response through Internet .The Internet browser displays the response (see figure 4)

.

Figure 4

If we don’t use a database, for every client request a new acquisition is necessary. For a large number of requests the system can break down.

To avoid the server break down there must be used use a tampon database (see figure 5).

Figure 5

The data acquisition system makes regularly data acquisition and saves data in databases.

A simple implementation of this method is made using WEB server MIIS (Microsoft Internet Information Server).

The script FOXISAPI (Fox Internet Server Application Interface) and the application Server_com.exe that includes the class clasacom1 with paginastart method that asks for data from database valori.dbf (see figure 6)

Figure 5

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