HTTP Server

The HTTP Server module is responsible for the dissemination of the hard disk images to any HTTP clients. If remote monitoring of the spectrum images is not required, this module does not need to be used. This module is specifically designed to work with the SpecSrv module and provides synchronized push functionality. A standard Web server could provide some of these features, but could not support push, on-demand, etc.

The design of the HTTPSrv is very conservative. It does not support any subdirectories. All requested URLs must be without any directory qualifiers. Behind the scenes, different source files for different browsers or languages are stored in subdirectories. However this is completely transparent to the user.

If a user requests "spec1.htm" on a Netscape browser in French, HTTPSrv will check sequentially:

Of course, if a user requests FR\Spec1.htm the server will respond with "file not found".

If a user with a Netscape browser requests an image file, the file will be delivered using push technology. The first push will happen immediately after the request and subsequent pushes will be synchronized with the acquisition of a new image from the SpecSrv. The SpecSrv module also reacts to these push-capable requests. Normally when a spectrum pane is in on-demand mode the first image downloaded will show "No demand". Within a few seconds the second image will be downloaded. This image should be an actual image since SpecSrv has noticed that it has a client for this pane. If an Internet Explorer browser is used this mechanism will not work and a refresh and pull must be used. This will not activate acquisition of SpecSrv. The mode for a pane may be set to "Enabled" to allow continuous access by non Netscape browsers. This should be avoided as it will probably result in the SpecSrv wasting time acquiring images that nobody is looking at.

If support of a large web site is required, it is suggested that the HTTPSrv should be only responsible for the SpecSrv related pages and linked into the main site. If the main web server is on the same computer HTTPSrv may be configured to use a non-standard port number. The main site could be and HTTPSrv could be (or some other port).