The cache directory for the proxy server has to be set up rather carefully with owner webuser and group webgroup, since it will be accessed by that insignificant person (see Chapter 2).
You now have to tell your browser that you are going to be accessing the Web via a proxy. For example, in Netscape click on Edit → Preferences → Advanced → Proxies tab → Manual Proxy Configuration. Click on View,and in the HTTP box enter the IP address of our proxy, which is on the same network, 192.168.123, as our copy of Netscape:
192.168.123.4
Enter 8000 in the Port box.
For Microsoft Internet Explorer, select View → Options → Connection tab, check the Proxy Server checkbox, then click the Settings button, and set up the HTTP proxy as described previously. That is all there is to setting up a real proxy server.
You might want to set up a simulation to watch it in action, as we did, before you do the real thing. However, it is not that easy to simulate a proxy server on one desktop, and when we have simulated it, the elements play different roles from those they have supported in demonstrations so far. We end up with four elements:
Netscape running on a Windows 95 machine. Normally this is a person out there on the Web trying to get at our sales site; now, it simulates a Butterthlies member trying to get out.
An imaginary firewall.
A copy of Apache (site: ... / site.proxy/proxy) running on the FreeBSD machine as a proxy server to the Butterthlies site.
Another copy of Apache, also running on FreeBSD (site: ... / site.proxy/real ) that simulates another web site “out there” that we are trying to access. We have to imagine that the illimitable wastes of the Web separate it from us.
The configuration in ... /site.proxy/proxy is as shown earlier. Since the proxy server is running on a machine notionally on the other side of the Web from the machine running ... /site.proxy/real, we need to put it on another port, traditionally 8000.
The configuration file in ... /proxy/real is:
User webuser Group webgroup ServerName www.faraway.com Listen www.faraway.com:80 DocumentRoot /usr/www/APACHE3/site.proxy/real/htdocs
On this site, we use the more compendious Listen
with the server name and port number combined.
Normally www.faraway.com would be a site out on the Web. In our case we dummied it up on the same machine.
In ... /site.proxy/real/htdocs there is a file containing the message:
I am a web site far, far out there.
Also in /etc/hosts there is an entry:
192.168.124.1 www.faraway.com
simulating a proper DNS registration for this far-off site. Note that it is on a different network (192.168.124) from the one we normally use (192.168.123), so that when we try to access it over our LAN, we can’t without help.
The file /usr/www/lan_setup on the FreeBSD machine is now:
ifconfig ep0 192.168.123.2 ifconfig ep0 192.168.123.3 alias netmask 0xFFFFFFFF ifconfig ep0 192.168.124.1 alias
Now for the action: go to ... /site.proxy/real,
and start the server with ./go - then go to
... /site.proxy/proxy, and start it with
./go. On your browser, access
http://192.168.124.1/. You should see the
following:
Index of / . Parent Directory . message
If we select message, we see:
I am a web site far out there
Fine, but are we fooling ourselves? Go to the browser’s proxy settings, and disable the HTTP proxy by removing the IP address:
192.168.123.2
Then reaccess http://192.168.124.1/. You should get some sort of network error.
What happened? We asked the browser to retrieve http://192.168.124.1/. Since it is on network 192.168.123, it failed to find this address. So instead it used the proxy server at port 8000 on 192.168.123.2. It sent its message there:[1]
GET http://192.168.124.1/ HTTP/1.0
The copy of Apache running on the FreeBSD machine, listening to port 8000, was offered this morsel and accepted the message. Since that copy of Apache had been told to service proxy requests, it retransmitted the request to the destination we thought it was bound for all the time: 192.168.123.1 (which it can do since it is on the same machine):
GET / HTTP/1.0
In real life, things are simpler: you only have to carry out steps two and three, and you can ignore the theology. When you have finished with all this, remember to remove the HTTP proxy IP address from your browser setup.