At the time of this writing both of the methods by which sniffle provides graphical data feedback to the client leave much to be desired. One method is to configure MS-Windows clients to spawn the Tektronix 222 DOS utility VIEW.EXE upon receipt of files with MIME type ``text/waveform'' and to configure the server to label outgoing .WFM files with this MIME type. Our second method is for the client to download waveforms to disk and then use a custom-written Matlab script to decode the .WFM file into a form intelligible to Matlab, which can then produce graphics.
Both of these methods are problematic because they are clumsy and insufficiently general. The first method only works with MS-Windows clients and requires client-end users to reconfigure their Web browsers. Much of the world uses X-Windows or Macintoshes, and reconfiguring a browser is a hassle beyond the abilities of most Web surfers. The second method requires even more special expertise than the first, as well as a custom-written Matlab script.
For these reasons it would be nice to have the sniffle server generate .GIF files from waveform data (or, for that matter, from the I/O board's analog and digital readings). This could be done in a two-stage process: waveform files are converted to ppm (``portable pixmap'') format by the sniffle program, and the resulting ppm data is converted to .GIF format by ppmtogif. The ppmtogif program is available on the Princeton Unix system and can probably be ported to DOS with minimal fuss. Read ``man ppm'' on the Unix system for more information on the portable pixmap file format. It's a very simple least-common-denominator format that can be understood in under five minutes. It is possible that many Web clients are configured to deal with .PPM files directly; I have not investigated the issue. The Windows graphics viewer LVIEWP is installed on our server PC and can be used to display .PPM files and can presumably be used as a client-end helper application.
Another option is to generate PostScript at the server. PostScript viewing utilities are available for most Web clients. PostScript can be generated directly, or perhaps with the help of a utility such as Gnuplot provided that the utility can be made to run in ``batch mode.'' The MS-Windows version of Gnuplot is installed on our server PC.
Yet another option similar to the current Matlab scheme, but which does not require custom software at the client end, would be to generate a generic plot file at the server and use something like Gnuplot at the client end to view the file. Gnuplot is available for X-windows and MS-Windows.