SAP GUI for HTML

SAP GUI for HTML Architecture 

SAP GUI for HTML Server

The SAP GUI for HTML is driven by the Internet Transaction Server (ITS). The ITS interfaces between a ‘stateless’ Web server (HTTP protocol), which communicates with Web browsers via single request/response cycles, and a ‘stateful’ SAP system (SAP GUI protocol), where running business transactions depends on internal status.

The following graphic shows one complete SAP GUI for HTML request/response cycle:

When the user starts a SAP GUI for HTML session from a Web browser, the request/response cycle comprises the following steps:

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       1.      The Web browser passes the request to the Web server.

       2.      The Web server loads the WGate (Web gateway), which is the Web server extension that links the ITS to the Web server.

       3.      The WGate sends the request data over a TCP/IP connection to the AGate (application gateway), which is the ITS core processing component.

       4.      The AGate loads the appropriate service file and uses the information stored there to establish a connection to the SAP system.

       5.      The SAP system responds by sending the logon screen back to the AGate.

       6.      The AGate uses either standard styles or a customer HTML template to generate an HTML page.

A style is a configurable set of rules that define how each user interface element found on an SAP transaction screen is mapped to HTML.

       7.      The AGate sends the generated HTML page back to the WGate.

       8.      The WGate passes the HTML page to the Web server.

       9.      The Web server passes the page to the user’s Web browser, which displays the result.

In order to maintain the user’s context in SAP system, the AGate maintains the connection to the SAP system during the entire SAP GUI for HTML session, but the link between the Web browser and the Web server is closed after each request/response cycle.

For every subsequent request after the session has been established, the Web browser uses cookies to send a session identifier with the HTTP request that uniquely identifies the connection to SAP system.

In each subsequent dialog step in the Web browser, the user changes a set of screen fields. The Web browser sends these fields to the Web server and WGate, which passes them to AGate. Thanks to the unique session identifier sent in the request data, AGate finds the connection to the SAP system and sends the changed screen fields to the SAP system along with an OK code. The SAP system returns a changed SAP screen that is converted to HTML either by using the standard styles or a customer’s own HTML template.