Understanding Original WebX and XML Client - System Connections

The Geo SCADA Expert server contains a web server that allows client PCs to access Geo SCADA Expert via a web browser over a secure network. The configuration of the web server, configured via the Server Configuration Tool, defines:

• The ports that are used by the web server to communicate with Original WebX clients and third-party XML clients. By default, Original WebX uses port 80 for non-secure XML and port 443 are used for secure XML.
• The SSL (Secure Socket Layer) certificate and key which encrypt communications between the web server and the Original WebX clients and XML clients (for added security)
  

For more information on these settings, see WebX Server Settings in the Geo SCADA Expert Guide to Server Administration.

To connect to the web server, a client PC has to use a web browser application such as Internet Explorer. There is no need for any other configuration on the client PC—as long as the client PC has a healthy connection to the Internet/Intranet, it can connect to the web server that is running on the Geo SCADA Expert server.

To establish the connection, you have to enter the address of the web server (and possibly the port number, depending on the configuration of your system) in the Address field of the web browser application.

When the connection between the Original WebX client or XML client and web server is established, the web browser launches an ActiveX Control that communicates with the Geo SCADA Expert web server. For users accessing the system via Original WebX, a log-on page or a homepage is shown.

As the user of the Original WebX or XML client accesses various displays such as Mimics and Trends, the ActiveX Control sends requests to the server via the Original WebX or XML client - system connection. These requests are used to retrieve the data and updates required for the displays on the client.

Normally, if a web browser is inactive, the browser will automatically close down its connection. To avoid the automatic connection closure, Geo SCADA Expert uses the ActiveX Control to continuously poll the Geo SCADA Expert server for updates. This updates the Original WebX and XML clients with the latest data so that the connections between the server and the Original WebX and XML clients remain active (and so do not close automatically). However, as the ActiveX Control has to poll the Geo SCADA Expert server for updates, it means that there is a greater demand for bandwidth—the Original WebX and XML clients are constantly requesting data to keep the connection open, even if the information on display has not been updated on the server.

The communications transmitted between the web server and the Original WebX and XML clients can be encrypted by using the SSL features of the Geo SCADA Expert server (see WebX Server Settings in the Geo SCADA Expert Guide to Server Administration). When these settings are in place, the Original WebX and XML - system connection can support secure (encrypted) and non-secure connections:

If a user accesses the system via an Original WebX or XML client that uses a http:// connection, the data that is transmitted and sent is non-secure, even if the web server is configured to utilize SSL.

If a user accesses the system via an Original WebX or XML client that uses a https:// connection, the data that is transmitted and sent is secure (encrypted). For this reason, those responsible for configuring the home pages and favorites of lower level users need to take care—if operators use http connections to access the system, the communications between the client and the system will not be secure.

Now that you understand how the connections are used, you can proceed to Connect to the System via an Original WebX Client or XML Client.