The tunnel feature consists of programs that are installed
on your Web server. These programs, called the tunnel feature's
server programs, use the Common Gateway Interface (CGI)
to receive requests from the Java applet running on a user's browser.
The server programs forward the requests to the SAS server for processing.
When the processing is complete, the programs return the results to
the applet.
The tunnel feature
is an optional feature that you can use with Java applets written
using the
SAS/SHARE driver for JDBC or the
SAS/CONNECT driver for
Java. It addresses two common configuration problems encountered with
Java applets that communicate with another machine:
-
A Java applet that is downloaded from a Web server is
not allowed to make socket connections to machines other than the
machine from which it was downloaded. This restriction means that
the SAS session would have to be started on the same machine as the
Web server from which the applets were downloaded.
-
Many firewalls prohibit applets
from establishing socket connections beyond the firewall. However,
most firewalls allow HTTP protocol to pass through the firewall, so
if the communication is done with HTTP protocol, applets are able
to communicate with servers that they would not normally be allowed
to communicate with.
Note: Java plug-in software, from
Sun Microsystems Inc. enables you to configure the way your applets
access machines on your network. If you are using the tunnel feature
to allow an applet to communicate with machines other than the Web
server from which it was downloaded, you can use the Java plug-in
software instead.
The tunnel feature can
solve both of these problems by virtually eliminating the restrictions
on where your SAS software runs in relation to your Web server and
firewall. In addition, because the tunnel feature gives you complete
control over who can access what, you gain these benefits without
sacrificing security for your vital data. The tunnel feature enables
you to greatly enhance the power and flexibility of the applets that
you create with the
SAS/SHARE driver for JDBC and the
SAS/CONNECT
driver for Java.