TweetFollow Us on Twitter

Serving From Home

Volume Number: 21 (2005)
Issue Number: 6
Column Tag: Programming

Serving From Home

Running A Mac Web Server With A Dynamic IPAddress

by Danny Swarzman

Introduction

With Mac OS X, the Macintosh has become an ideal platform for developing web applications. It includes an Apache server. All the services you want -- FTP, PHP, Perl, mySQL, Tomcat, etc. -- are either included with OS X or are available for free. You can test the client side on the same Macintosh that is running the server. You can edit web files with a regular text editor without an extra step to transfer them to a server.

Some accounts offered by Internet service providers don't offer all these services. Some accounts don't include access to the unix shell or don't allow you to view system log files- useful when you are debugging client-server communications. It would be helpful if you could use your home computer as a web server.

But there is a snag. A commercial Internet Service provides a static Internet Protocol address. When a user types an address into a browser, that address is sent to specialized servers on the Internet, Domain Name Servers. They locate the static IP address corresponding to the domain name.

If you are connected to the Internet via a cable or DSL service in your home, you don't have a static IP address. Instead, you have an address that can change every time you start you computer. It may even change while you computer is running. You can't have a domain name assigned to your home server.

This article shows a way that you can use a commercial Internet Service Provider account to act as your personal name server. The user enters the address of a web page on the commercial account. That page redirects the request to your home computer.

The load on the commercial server is very low. Once it's set up, you never need to change it. You may be able to use a friend's account. The only requirement for the commercial server is that it can run scripts in perl or some similar language. All the changes that you make on your site after that are on the home Macintosh.

The commercial server needs to know the Internet Protocol address currently assigned to your home computer. A script running periodically on home computer periodically sends a message to the commercial server to inform it of the home computer's address. `

The method has its drawbacks. I'm not suggesting this as a replacement for a static IP address for commercial or high volume applications. It is, however, handy for demonstrations and uses that don't demand 100% reliability.

Overview

The basic idea is very simple. This process uses two web servers: one on your Macintosh at home (hereafter called the Home Server), and a commercial server (hereafter called the Redirection Server). The Home Server periodically runs the script ip_to_server.pl. That script sends a request to the Redirection Server. The request contains the Home Server's IP address. The Redirection Server responds with the script ip_to_file.pl which saves the Home Server's IP address in a file. When a browser sends a request to the Redirection Server, the Redirection Server uses the saved IP address to redirect the client's request for a web page to the Home Server. (See Figure 1.)

For example suppose that the saved IP address is 92.2.92.2 and the address of the Redirection Server is http://stowlake.com/. The user enters or clicks on a link to:

http://stowlake.com/redirect.pl?xfile=some.html

The script redirect.pl redirects the request to the file specified by the xfile parameter on the Home Server:

http://92.2.92.2/some.html


Figure 1. Putting it all together.

This method has several limitations. First, of course, the Home Server needs to be turned on all the time that someone may want to access the pages involved. Also, there can be a lag between the change in the IP address on the Home Server and latest cycle of saving the IP address on the Redirection Server. When that happens, the client will fail to get the right page. The frequency with which a dynamic IP address changes depends upon the quality of the DSL connection. It can vary between several times per hour to several times a week. Do some experiments.

Configuring the Redirection Server

Let's get into specific details. First, let's see how to configure the Redirection Server. You can use any commercial Internet server that supports Perl or some other convenient language. Our examples are in Perl. One script stores the IP address of the Home Server. Another retrieves that address when it needs to redirect a request from the web client.

Remembering the Home Server's IP Address

In response to a request from the Home Server, the script ip_to_file.pl stores the address of the sender. Listing 1 shows this script.

Listing 1: Caching the Home Server's Address

ip_to_file.pl

#!/usr/bin/perl -w
# Save IP address received from Home Server to file.

use CGI qw(:standard);

$ipfile = 'home_server_ip';
print header,start_html;
if(open IPFILE, ">$ipfile")
{
   $ip = $ENV{REMOTE_ADDR};
   print IPFILE $ip."\n";
   close IPFILE;
   print "Wrote to file $ipfile: $ip";
}
else
{
   print "Failed to open file $ipfile for writing.";
}
print end_html;

This script is a CGI script that sends back a response that contains the IP address that it just saved.

Redirecting to the Home Server IP Address

The redirection script redirect.pl is shown in Listing 2. It takes a single parameter, 'xfile'. That is the filepath on the Home Server to which the request will be redirected.

Listing 2: Redirecting to the Home Server's address

redirect.pl

#!/usr/bin/perl -w
# Save IP received from Home Server.

use CGI qw(:standard);

# Redirect a request to the Home Server.
# The file to which to redirect is specified by parameter xfile.
# The IP address of the Home Server is retrieved from the file.

$ipfile = 'home_server_ip';
$fileOnHomeServer = param('xfile');

if(defined($fileOnHomeServer))
{
   if(open IPFILE, "<$ipfile")
   {
      chomp ($ip = <IPFILE>);
      print "Location: http://$ip/$fileOnHomeServer\n\n";
   }
   else
   {
      print header,start_html;
      print "Failed to open file $ipfile";
   }
}
else
{
   print header,start_html;
   print "Failed to retrieve file to access.";
   $fail=1;
}
print end_html;

Configuring the Home Server

The script in Listing 3, ip_to_server.pl, sends a request to ip_to_file.pl on the Redirection Server. The IP address of the sender is automatically sent with an HTTP request. There doesn't need to be any special code in ip_to_server.pl for that.

Listing 3: Sending an address to the Redirection Server

ip_to_server.pl

#!/usr/bin/perl -w

use LWP::UserAgent;
use HTTP::Request::Common qw(GET);

# Send a request to the Redirection Server to save this computer's IP
# 
# Server finds the IP in the request, saves it and returns 
# the IP in its response.
#
# This script records its transactions in a log file.
#
$kRedirectionServerAddress = 
   'http://www.stowlake.com/cgi-bin/ip_to_file.pl';	
open LOGFILE, ">>/tmp/ip_to_server.log" 
   or die "Couldn't open ip_to_server.log $!\n";
print LOGFILE scalar(localtime());
my $userAgent = new LWP::UserAgent;
my $request = GET $kRedirectionServerAddress;
my $response = $userAgent->request($request);
my $success = $response->is_success();
my $found = 0;
if( $success )
{
   my $content = $response->content;
   if ( $content )
   {
      my @data = split /\n/, $response->content;
      for(@data)
      {
         if(/Wrote to file/)
         {
            print LOGFILE "   ip was updated to: ";
            /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/;
            print LOGFILE $1."\n";
            $found = 1;
         }
      }
   }
}
else
{
   print LOGFILE "Failed to contact server: \n".
      $response->error_as_HTML."\n";
}
print LOGFILE "failed to update ip\n" if !$found;

Setting It Up

So we've got a couple of Perl scripts at hand. How do we set this thing in motion?

Upload Scripts to the Redirection Server

First, we need to upload the two scripts ip_to_file.pl and redirect.pl to the redirection server. Most ISP's allow you to upload files using the File Transfer Protocol (FTP). I typically use the application Fetch 4.0.3 to do this. You may of course prefer other tools.

Depending on your ISP, there may be a specific folder into which you put CGI scripts. For mine, cgi-bin is its name and it appears when I connect to their FTP site. Check with yours. They may set up the files differently. Whatever folder you use, you need to set the file permissions to allow execution of the scripts. In Fetch, use "Set Permissions..." in the Remote menu. Check the boxes as shown in Figure 2 for each of the Perl scripts.


Figure 2. Setting File Permissions

If you have access to the UNIX shell on your Redirection Server, you can set permissions with the shell commands:

chmod 755 ip_to_file.pl
chmod 755 redirect.pl

Once the files are in place, you can test them from a web browser. Enter the URL for ip_to_file. In my case, it's:

http://www.stowlake.com/ip_to_file.pl

A message with the IP address of your home Macintosh should appear in the browser window. Look for a file on your ISP site called home_server_ip. It should be in the same directory as ip_to_file.pl.

Start the Web Server on the Home Macintosh

Next we need to start the server on the home machine. Open the System Preferences application and choose the Sharing panel. Check the box labeled Personal Web Sharing, as in Figure 3.


Figure 3. Starting the Web Server

Put a sample web page into the directory /Library/WebServer/Documents on the boot drive. If you file is called some.html, type this into a web browser's address box:

http://localhost/some.html

If you see the page, your web server is running.

Run a Script on the Home Macintosh Periodically

The final piece of the puzzle is to run the ip_to_server.pl script on the Home Server. Modify the sample file to user your Redirection Server by changing the value of $kRedirectionServerAddress to the address of the directory on the Redirection Server that contains the scripts you put there. Put ip_to_server.pl in a convenient place on your Macintosh. I chose /Library/WebServer/CGI-Executables.

Make the script executable. Open the Terminal application. The Terminal application is in the Utilities subfolder of the Applications folder in the main drive. Go to the directory to where you put ip_to_server.pl and change the permissions. For example:

cd /Library/WebServer/CGI-Executables
chmod 755 ip_to_server.pl

Now try running the script. Just enter:

./ip_to_server.pl

You can tell if it worked with this command:

cat /tmp/ip_to_server.log

You should see a message in the terminal window telling you that the IP address was updated.

Finally, you need to get the script to run periodically, in my case every 10 minutes. You need to use the command, crontab, in the Terminal application. There is a program that is always running, the cron daemon. It periodically scans the table created by the crontab command. For each entry, if its time has come, cron calls the associated command. (You may want to review crontab documentation. Type "man crontab" into the Terminal application. Or, you can use the application ManOpen to view man pages.)

The first step is to create a file that specifies when ip_to_server.pl is to run. Let's call it ip_to_server.crontable. This example says: execute the specified command at 0 minutes, 10 minutes, ..., after the hour. Repeat every hour of every day of every month, including every day of the week. The contents of ip_to_server.crontable is this one line:

0,10,20,30,40,50 * * * * /Library/WebServer/CGI-Executables/ip_to_server.pl

Next enter a command in the terminal window:

sudo crontab -u username ip_to_server.crontable

(For username, substitute your login name on your Macintosh.)

Finally to verify:

crontab -l

The last command displays contents of the cron table just created.

Conclusion

Many of us may have thought that signing up for Internet services that use a dynamic IP address was thereby to give up any hope of serving web pages from our home computers. As I've shown in this article, a dynamic IP address is really no barrier to doing this. Rather, we simply need to upload a few simple Perl scripts to the Redirection Server and then periodically update the stored IP address by running a local cron job. As we've seen, this is not an industrial-strength solution, but it's probably fine for letting your relatives view photos from your recent trip to Hawaii or peruse your weblog. You need to experiment to know how it works for you.

References and Credits

ManOpen is a Macintosh application to easily view man pages. You can scroll through them, follow links from man page to man page and print man pages.

http://www.clindberg.org/projects/ManOpen.html

Bob Ackerman showed me how to do what I've described here. The sample code in this article was inspired by his example. He also reviewed this article. Thanks also to Victoria Leonard for her helpful suggestions and to Tim Monroe for his editing assistance.


Danny Swarzman writes programs in JavaScript, Java, C++ and other languages. He also plays Go and grows vegetables. You can contact him with comments and job offers at dannys@stowlake.com and http://www.stowlake.com.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

CleanMyMac 3.9.2 - $39.95
CleanMyMac makes space for the things you love. Sporting a range of ingenious new features, CleanMyMac lets you safely and intelligently scan and clean your entire system, delete large, unused files... Read more
Printopia 3.0.4 - Share Mac printers wit...
Run Printopia on your Mac to share its printers to any capable iPhone, iPad, or iPod Touch. Printopia will also add virtual printers, allowing you to save print-outs to your Mac and send to apps.... Read more
Tinderbox 7.3.1 - Store and organize you...
Tinderbox is a personal content management assistant. It stores your notes, ideas, and plans. It can help you organize and understand them. And Tinderbox helps you share ideas through Web journals... Read more
ExpanDrive 6.1.6 - Access cloud storage...
ExpanDrive builds cloud storage in every application, acts just like a USB drive plugged into your Mac. With ExpanDrive, you can securely access any remote file server directly from the Finder or... Read more
Printopia 3.0.4 - Share Mac printers wit...
Run Printopia on your Mac to share its printers to any capable iPhone, iPad, or iPod Touch. Printopia will also add virtual printers, allowing you to save print-outs to your Mac and send to apps.... Read more
Tinderbox 7.3.1 - Store and organize you...
Tinderbox is a personal content management assistant. It stores your notes, ideas, and plans. It can help you organize and understand them. And Tinderbox helps you share ideas through Web journals... Read more
ExpanDrive 6.1.6 - Access cloud storage...
ExpanDrive builds cloud storage in every application, acts just like a USB drive plugged into your Mac. With ExpanDrive, you can securely access any remote file server directly from the Finder or... Read more
VOX 3.0.1 - Music player that supports m...
VOX just sounds better! The beauty is in its simplicity, yet behind the minimal exterior lies a powerful music player with a ton of features and support for all audio formats you should ever need.... Read more
Merlin Project 4.3.3 - $289.00
Merlin Project is the leading professional project management software for OS X. If you plan complex projects on your Mac, you won’t get far with a simple list of tasks. Good planning raises... Read more
Mac DVDRipper Pro 7.1 - Copy, backup, an...
Mac DVDRipper Pro is the DVD backup solution that lets you protect your DVDs from scratches, save your batteries by reading your movies from your hard disk, manage your collection with just a few... Read more

Latest Forum Discussions

See All

Animal Crossing: Pocket Camp mid-game gu...
By this point, you've probably hit or surpassed mid-way inAnimal Crossing: Pocket Camp.The game changes quite a bit as your focus slowly shifts from endlessly fulfilling requests for campsite buddies to improving your amenities. Here are a few tips... | Read more »
Mille Bornes (Games)
Mille Bornes 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: | Read more »
Blob gets a new look in Give It Up! 3
Blob makes his triumphant return, as Yoozoo Games and Invictus Gaming have joined forces to create Give It Up! 3, the third in a series of delightful action-adventure games featuring our wobbly friend Blob. In this newest adventure, you’ll get to... | Read more »
148Apps' Ultimate Guide to Black Fr...
Black Friday is here, and there are a whole lot of discounts running right now for folks on the lookout for new mobile devices, accessories, and yes, even games. Here's a helpful rundown of what you'll find both in stores and online. Happy... | Read more »
The best Black Friday mobile game deals
Black Friday's upon us, and if you've happened to nab a fancy new phone during the week's big savings, you might be searching for some new games to fill up space on your new gadget. There are a lot of great games on sale right now for Black Friday... | Read more »
The best mobile games to play while your...
Thanksgiving is a time to reconnect with loved ones, eat lots of food, and all of that jazz, but once the festivities start to wind down, folks tend to head to the couch to watch whatever football is happening for Turkey Day. | Read more »
The best Black Friday deals for Apple ga...
Black Friday is hours away at this point, but many popular retailers are getting a jump on things with plenty of pre-Black Friday sales already available. Many of those early bird sales including some sharp discounts on the latest Apple phones... | Read more »
The Inner World 2 (Games)
The Inner World 2 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Solve mind-bending puzzles in a world full of mystery and save the family of the flute-noses! Their dynasty has been... | Read more »
warbot.io wants you for the robot wars
Fans of epic gundam-style battles will find a lot to love in warbot.io, the first game for up and coming developer Wondersquad. The game saw a lot of success when it first launched for browsers and Facebook, and now even more people are getting the... | Read more »
Uncover alien mysteries in cross-genre s...
If the Alien franchise taught us anything, it’s that landing on a strange planet at the behest of a faceless corporation is probably asking for trouble. And Eldritch Game’s Deliria doesn’t prove otherwise. In 2107, Dimension LG7 is rich with... | Read more »

Price Scanner via MacPrices.net

Apple 9″ 32GB iPad for $80 off on Walmart onl...
Snag a 9.7″ 32GB WiFi iPad for $249 on Walmart’s online store as part of their Black Friday sale. That’s $80 off MSRP, and it’s the lowest price available for an iPad so far this season. Sale price... Read more
Apple Black Friday sale for 2017: $150 Apple...
BLACK FRIDAY Apple has posted their Black Friday deals for 2017. Receive a $150 Apple gift card with the purchase of select Macs and up to $100 with various iPads, iPhones, and Apple Watches. The... Read more
Black Friday 2017: Where to find the best dea...
B&H Photo has 15″ and 13″ MacBook Pros on sale for up to $200 off MSRP as part of the Black Friday and Holiday sale. Shipping is free, and B&H charges sales tax for NY & NJ residents only... Read more
Black Friday 2017: Where to find the best dea...
B&H Photo has 12″ MacBooks on sale for $150 off MSRP as part of the Black Friday and Holiday sale. Shipping is free, and B&H charges sales tax for NY & NJ residents only: – 12″ 1.2GHz... Read more
Black Friday 2017: Where to find the best dea...
B&H Photo has 10.5″ iPad Pros in stock today and on sale for up to $130 off MSRP. Each iPad includes free shipping, and B&H charges sales tax in NY & NJ only: – 10.5″ 64GB WiFi iPad Pro... Read more
Black Friday 2017: Where to find the best dea...
B&H Photo has 13″ MacBook Airs on sale for up to $150 off MSRP as part of the Black Friday and Holiday sale. Shipping is free, and B&H charges sales tax for NY & NJ residents only: – 13″... Read more
Black Friday 2017: Where to find the best dea...
B&H Photo has 27″ and 21″ iMacs on sale for up to $200 off MSRP as part of the Black Friday and Holiday sale. Shipping is free, and B&H charges sales tax for NY & NJ residents only: – 27... Read more
Black Friday 2017: Where to find the best dea...
B&H Photo has Mac minis on sale for $100 off MSRP as part of their Black Friday sale, each including free shipping plus NY & NJ sales tax only: – 1.4GHz Mac mini: $399 $100 off MSRP – 2.6GHz... Read more
Black Friday 2017: Find the best deals and lo...
Scan our exclusive price trackers for the latest Black Friday 2017 sales & deals and the lowest prices available on Apple Macs, iPads, and gear from Apple’s authorized resellers. We update the... Read more
Black Friday: 27″ 3.4GHz iMac for $1599, save...
Amazon has the 27″ 3.4GHz Apple iMac on sale for $1599.99 as part of their Black Friday sale. That’s $200 off MSRP, and shipping is free. Their price is currently the lowest price available for this... Read more

Jobs Board

Information Systems Engineer, *Apple* Retai...
# Information Systems Engineer, Apple Retail Engineering Job Number: 112895982 Santa Clara Valley, California, United States Posted: 02-Oct-2017 Weekly Hours: 40.00 Read more
Commerce Engineer, *Apple* Media Products (...
# Commerce Engineer, Apple Media Products (New York City) Job Number: 113028813 New York City, New York, United States Posted: 20-Sep-2017 Weekly Hours: 40.00 **Job Read more
Business Development Manager, *Apple* Pay -...
# Business Development Manager, Apple Pay Job Number: 112919084 Santa Clara Valley, California, United States Posted: 18-Aug-2017 Weekly Hours: 40.00 **Job Summary** Read more
Digital Marketing Media Planner, *Apple* Se...
# Digital Marketing Media Planner, Apple Services Job Number: 113080212 Culver City, California, United States Posted: 03-Oct-2017 Weekly Hours: **Job Summary** Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.