The Web Server Gateway (WGate) links the ITS to the Web server by receiving requests from the Web browser via the Web server and forwarding them to the AGate using TCP/IP.
The WGate resides on the same machine as the Web server, where it acts as a Web server extension and shields the AGate from differences in the various Web server APIs. The WGate supports Web servers such as Microsoft Internet Information Server (IIS), Sun ONE Web Server and Apache Web Server.
The WGate has the simple task of sending requests from the Web server to the AGate and also sending back the response from the AGate to the Web server. It is always installed on the same host where the Web server is. To minimize any threat of attacks, it is designed to be the only bridge between the Web server and the AGate.
The WGate connects a “stateless” Web server, which communicates with Web browsers via single request/response cycles, to a “stateful” SAP system where business transactions depend on the internal status.
When an Internet or intranet user starts an application from a Web browser and triggers an SAP transaction, function module or report via the ITS, a server process must be running throughout the user session (possibly longer) to maintain the user’s context in the SAP system. Although communication between the Web browser and the Web server is based on single request/response cycles, the WGate must be able to transfer the browser request to a permanently running AGate server process.
Due to the load balancing capabilities of the ITS, the WGate must be able to route requests and responses to the appropriate AGate (an ITS session must always be handled by one and the same AGate and the WGate takes care of this).
The following figure shows a Browser-to-WGate request, where the Browser connects to the Web server via HTTP or HTTPS. The WGate runs as a plug-in in the Web server.