ISSymbol Control Layer

ISSymbol is a component designed by InduSoft that is able to display the screens created with IWS in the Web browser and exchange data (tag values and history data) with the TCP/IP server module of the project. On the Thin Client station, the Web browser (e.g., Internet Explorer) is the container that hosts the ISSymbol control.

ISSymbol works as a control layer between the project and the Web browser — equivalent to the Java Virtual Machine for Java-based applications. This approach provides a high level of security because ISSymbol does not allow the project to access the operating system directly.

When the Web browser downloads the HTML page specified by the user, it checks for ISSymbol control registration on the current computer. If it does not find it, the browser attempts to download registration from the URL specified in the project settings (Thin Client on the Project tab of the ribbon). The Web browser is not able to display the screens from the project if the ISSymbol control is not properly registered in the Thin Client station.

CAUTION:

Make sure your Web browser is enabled to download signed ActiveX controls, in order to download ISSymbol automatically. Otherwise, you will need to register ISSymbol manually in the Thin Client station. Check your Web browser's documentation about security settings if you have questions about how to configure these settings.

Manually Installing the ISSymbol Control

You can also install the ISSymbol control manually in the Thin Client station. The procedure to install ISSymbol in each operating system is described below:

Windows PC

Copy the following files…
- […]\InduSoft Web Studio v7.0\Bin\ISSymbolReg.exe
- […]\InduSoft Web Studio v7.0\Bin\ISSymbolVM.cab
…into any directory of the Thin Client station. Make sure that both files are stored in the same directory.
Run ISSymbolReg.exe to register the ISSymbol control on the PC.

Windows Embedded

Determine the OS version and processor type of the Windows Embedded device, and then find the corresponding redistribution folder in the IWS program directory:
```
[…]\InduSoft Web Studio v7.0\Redist\CE_version\processor_type\Bin\
```
For example, for a MIPS IV processor running Windows CE 5.0 or later:
```
[…]\InduSoft Web Studio v7.0\Redist\WinCE 5.0\MIPSIV\Bin\
```
From that directory, copy the following files…
- IndHTTP.dll
- IndVkStd.dll
- ISSymbolCE.ocx
…and one of the following Virtual Keyboard layouts…
- VKEN.ini (for English)
- VKGE.ini (for German)
…into any directory in non-volatile memory on the Windows Embedded device. Make sure that all files are stored in the same directory.

At the Windows command prompt, execute the following command:

regsvrce.exe "\ISSymbol_directory\ISSymbolCE.ocx"

For example:

regsvrce.exe "\Storage Card\ISSymbolCE.ocx"

Save the registry settings to keep ISSymbolCE.ocx registered when you reboot the Windows Embedded device.

Windows Mobile / Pocket PC

Follow steps 1 and 2 of the instructions for Windows Embedded (above).
Run the program RegSvrCE.exe on the Windows Mobile device. While in the program, do the following:
1. Locate the file ISSymbolCE.ocx in the directory to which you copied it.
2. Select the Register option.
3. Click OK.

Tip: Your Windows Mobile device may not come with the program RegSvrCE.exe, because such consumer devices (i.e., smartphones and PDAs) are typically not meant to be used like this. If you need to acquire this program — or VBScript.dll, which is also left off most Windows Mobile devices — then please contact Customer Support.

How It Works

After you open the Web browser, you must type the URL for one web page available in the Web Server station (e.g., http://127.0.0.1/main.html) into the Address field. At this point, the Thin Client executes the following process:

The Web browser downloads the HTML page of the screen you specified.
The Web browser checks for ISSymbol control registration in the local computer. If it does not find it, the Web browser attempts to download the ISSymbol component from the URL configured in the project (settings saved in the HTML page). Since the ISSymbol control is properly registered in the Thin Client station, the Web browser loads it.
From this point on, ISSymbol takes over the communication with the server station, and the Web browser is used only as a host for ISSymbol.
ISSymbol connects to the data server. You configure the data server IP Address in the project settings (Thin Client on the Project tab of the ribbon). This setting is embedded in the HTML page.
ISSymbol prompts a window on the Thin Client, asking for the User Name and Password. The data you enter is codified by Binary Control and sent to the server. The server station checks the validity of the data and whether you have the rights to open the startup screen. If so, the process continues. If not, you are prompted with an error message indicating that the User Name and Password are invalid. In this case, the process will not continue.
Note: Step 4 is skipped if the Security System is disabled during the configuration of the project.
ISSymbol downloads the necessary files to display the screen specified by the user (screen files, tags database, translation files and so forth).
ISSymbol connects to the data server and reads the value of the tags that are displayed in the screen you specified.
ISSymbol displays the screen on the Web browser and keeps updating the objects according to the values read from the server. Whenever the value of any tag displayed on the open screen(s) changes on the server, the new value is sent to the Thin Client (and vice-versa). Therefore, there is no pooling between the Thin Client and the server station. This method increases the communication performance and optimizes the traffic in the network.

Notice that there are two servers in this process:

Web server (HTTP Server): Provides the files from the server to the Thin Client via HTTP protocol over TCP/IP.
Data server (TCP/IP Server module from IWS): Provides tag values and/or history data from the project running on the server to the Thin Client station(s).

Although both servers are usually running in the same computer, IWS provides the flexibility to run each server in a different station, if necessary. See Web-based application typical architectures for further information.