Using
Client Pull Technology with eComet Applications
This
tip explains how to use your web browser’s client pull technology to
automatically display two web pages in sequence. This can be very useful for
some eComet applications. For example, suppose you create an eComet program
that processes a large amount of data before displaying the results. While the
user is waiting to see the web page, you might want to display a message such
as “Please wait while your information is being prepared…”
Here’s
how to make this happen. You will need to create two eComet programs:
Here’s
a picture of the process:
Here
are the HTML commands that your first eComet program must send to the web
browser:
<HTML>
<HEAD>
<TITLE>
Please wait while your information is being
prepared…
</TITLE>
<META HTTP-EQUIV=”Refresh” CONTENT=”0;
URL=fully-qualified-url”>
</HEAD>
<BODY>
Please wait while your information is being
prepared…
</BODY>
</HTML>
Notice
the <META> tag in the <HEAD> section. This tag instructs the web
browser to refresh the page by pulling a new web page from the eComet server.
The CONTENT parameter contains the important details:
CONTENT=“0; means to refresh the page after 0 seconds
(immediately).
URL=fully-qualified-url” contains the full URL of the
second eComet program, including domain name, port number (if it’s something
other than the default value of 80), and program name (including the /xap
prefix).
For
example, if the second eComet program was named PULL2 and was located on
signature.net, port 8080, the <META> tag would be:
<META HTTP-EQUIV=”Refresh” CONTENT=”0;
URL=http://comet.signature.net:8080/xap/pull2”>
As
a result, the first eComet program displays the “Please wait…” message and
immediately starts the second eComet program running on the server. The wait
message remains on the browser screen until the second program starts to
display its output.
The
client pull concept is further demonstrated in the BLAST2 program (source name
is XBLAST2) in the eComet tutorial.
The
major web browsers, including Internet Explorer and Netscape Navigator, support
client pull technology. See the following web page for more information:
www.netscape.com/assist/net_sites/pushpull.html