Additional Web-to-Host Solutions

Other web-to-host solutions are available from third-party vendors; however, there are drawbacks to using these technologies.

A solution adopted by many third-party host-connectivity providers involves "on-the-fly" conversion of 3270 data streams to HTML code. By using standard HTML code, this solution works with all web browsers and does not require the downloading of an "applet" or other client-side code.

This method of web-to-host integration is limited by the restrictions of HTML code and the web’s client/server architecture. Representations of host sessions are usually crude in appearance with no support for screen-scaling, file transfers, Automation scripting, or other features found in stand-alone terminal emulators.

The web browser is also limited because it only supports "stateless" conditions–that is, the web server does not retain any client state information between client requests. This can lead to synchronization problems between the host application and the host display as interpreted by the web browser and the 3270-to-HTML conversion utility. In contrast, the SNA Server Web Client establishes an end-to-end session with the host system, thereby avoiding this problem.

A second popular solution involves using "screen-scraping" techniques to scan a host application display and convert strings of characters into HTML data. As with 3270-to-HTML conversion utilities, these solutions can be accessed with any browser. However, you can create more attractive interpretations of host data from applications not exclusively created for the 3270 data stream.

Because this technique relies on the physical layout of host screens, any changes made to the screen format or text orientation may cause applications to fail. Using this technique to create web-based client/server applications is usually more labor-intensive than using COM Transaction Integrator, OLE DB Provider, the ODBC/DRDA Drivers, or other programmatic features of SNA Server.