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3270 Web Gateways
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Host Access Web Gateways provide protocol conversion of screen formats and content for use in standard Web browsers.  Screensurfer Connects 3270 and 5250 sessions to Web Browsers Types of Gateways Web Gateways can be categorized as follows:
Of these categories, Screensurfer can be programmed and configured to provide any or all of the first three. A brief description of each category follows. HTML Session-based Terminal Emulator The HTML Session-based gateways provide a pass-through capability enabling users to connect and interoperate with host applications in a very similar fashion to standard terminal emulation. The main difference is that screens are presented as HTML pages, with entry fields (unprotected fields) displayed as graphical input fields. With Screensurfer, the user is also able to review any prior screen using the browser back-button; a feature not available in a conventional terminal emulation environment.
This access approach is fast and direct, offering access without any client installation processes or lengthy start-up downloads.
Some products, including Screensurfer, provide the ability to enhance some or all of the screens into customized HTML formats. In some cases this may be required simply to make the application usable in a browser; in other cases it can exploit the information formatting capabilities of the browser to improve the usability and effectiveness of the application.
HTML Dynamic Information Pages This kind of Web Gateway provides the ability for a department or organization to define special URL's (universal resource locators--such as "http://www.inventu.com/helpdesk"). The gateway provides a means to program navigation to and presentation of specific information based on the URL submitted. Uses include customer service applications where, for example, the user can enter a package number and view shipping status for that package.
This kind of gateway provides the highest degree of compatibility with the way casual information seekers work with their browsers. Each viewed page can be bookmarked and easily returned-to in subsequent browser sessions.
The downside of this approach is that each URL must be custom-coded, including any requisite navigation from the logon-screen to the screen(s) providing the information.
Client/Server 3270/5250 Middleware The Client/Server 3270/5250 middleware gateway acts as an information retrieval engine, accepting requests from client programs executing somewhere on a private or public network. It answers these requests with formatted information which is then available to the client program. This is essentially a remote procedure call server for 3270 and 5250-based information.
This kind of gateway shares many development requirement with the dynamic information page gateway, in that it needs to have programmed into it navigation and formatting characteristics for specific information.
Screensurfer provides this capability to Cold Fusion applications using a custom CFX tag (CFXSurfer) as well as Microsoft Active Server Pages (ASP) applications using an ASP-extension COM object (SSurfer.ASPRequest). In addition, using its exclusive granular pass-through tags, Screensurfer can seamlessly blend the middleware approach with pass-through of any number of screens without any additional programming.
Java Terminal Emulator The Java-based terminal emulator is a 3270 or 5250 emulator that has been ported or newly written using the Java language and class libraries. It may require a proprietary server or perform direct TN3270/TN5250 emulation using the new security flexibility in the latest versions of Java.
As a user of a web browser starts this type of emulator, a new desktop window is usually launched, and the user is essentially disconnected from the browser while interacting with the emulation window. We call this the emulator in a box.
This approach requires a download of the base emulation classes or an installation process prior to viewing the first screen, which may represent a considerable delay. Other issues with this approach include print-screen incompatibility with any but the very latest browsers, or requiring a "hack" workaround with a dummy browser window and operator intervention.
With a Java emulator, any enhancements to the user interface will be made at the client side, increasing the volume of download data and increasing maintenance headaches as host screen modifications are made over time. Enhancements in this environment are performed the same way as they have been for the last 10 years in the PC-with-emulator environment, with many issues involving complete "re-write" of the user interface from screen to graphical user interface, including all of the programming difficulties inherent in GUI development.
Platform-specific terminal emulator This form of gateway is really not a gateway at all, but is instead a repackaging of existing terminal emulation code into web-deliverable components. These may be plug-ins for the Netscape environment, or ActiveX controls for the Microsoft environment.
This approach reduces client PC maintenance in some aspects, while not improving delivery opportunities a great deal. Users still need to have a compatible platform, such as a Windows/95 or Windows/NT machine.
Enhancing the user interface must be accomplished using traditional platform-development tools, such as Visual Basic. The productivity of this type of enhancement as well as the maintenance problems it introduces has made it an unpopular approach in many organizations.
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