HTTP Example Server
by Keith Vogel
HomePage.htm, and this page must exist at the root of the SD file
system. All files on the SD file system must be limited to the
8.3 file naming
convention; appropriate extensions should be used on your files. The SD file
system can contain HTML pages, JPEGs, GIFs, ICOs, TXT, MPEGs, WMVs, and XMLs for
download to the browser; however, only the three-letter extensions may be used for
each file type. The content type specified to the requesting browser is determined by
the three-letter file extension.
In addition to pages stored on the SD card, it is possible to add active pages that are dynamically created by writing a
compose function and specifying the
accessing URL to the server. These dynamic pages can respond to browser HTTP
GETs, PUTs, or POSTs and can dynamically interact
with the resources on the chipKIT board. One example is to create a dynamic page
that talks to a camera that is connected to the board, and then have it take a
picture and compose a JPEG picture. In designing your HTML pages you can use URLs
that reference local SD files, dynamically created pages, or absolute URLs to other
sites embedded in your HTML pages. For example, if you want to see some locally
hosted pages on the SD card, checkout the page about The
chipKIT MPIDE System. Or, you can go to another site like the Digilent products
page at Digilent Inc.
The HTTP Server uses a highly cooperative embedded programming model where multiple connections and pages can be processed concurrently. To ensure this works reliably, any code written for the server’s
loop() function or composing pages
should be written as a state machine, with each state only doing a small portion of
work. The HTTP server loops repeatedly, calling your code as well as the HTTP server
code. As part of the HTTP server code, it listens for connections. When a
connection is made, the appropriate compose() function is called based
on the URL. If no URL matches a compose page, the
default compose() function is called. Typically, the SD file system
compose function is used as the default compose() function, as this will
look on the SD file system for a matching file. If no file exists, the
SD compose() function will return an “HTTP File Not Found
(404)” error to the browser.
For specific information on how to set up this example server, goto SrvSetup.htm.