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IP address and Host name Scripts

robert hashemian

As some of you know, this site contains several utilities in the tools section. One of these tools is JavaScript Visitor IP Address and Host Name. It's a simple JavaScript block that can be placed inside any web page and it displays or prints the visitor's IP address and host name.

As is with the rest of the tools, this one was also born out of necessity and I decided to share it with everyone. But some people are not comfortable putting my scripts on their site. That's cool and I don’t blame them, they don’t know me. So here I am going to explain how to display or print the user's IP address and host name using a number of server-side technologies.

The keyword here is "server-side". That's right, there is no way you can glean that information from client-side JavaScript. Even my JavaScript utility uses server-side calls to obtain the data and then packages it up in JavaScript format and streams it back. If your site supports server-side scripting, then chances are one of the following will do the job for you.

  • Perl:
    • print "IP: $ENV{'REMOTE_ADDR'}<br>Host: $ENV{'REMOTE_HOST'}";

  • SSI:
    • IP: <!--#echo var="REMOTE_ADDR"--><br>Host: <!--#echo var="REMOTE_HOST"-->

  • PHP:
    • <?= "IP: {$_SERVER['REMOTE_ADDR']}<br>Host: {$_SERVER['REMOTE_HOST']}" ?>

  • ASP:
    • <%= "IP: " + Request.ServerVariables("REMOTE_ADDR") + "<br>Host: " + Request.ServerVariables("REMOTE_HOST") %>

  • ASP.NET:
    • <%= "IP: " + Request.UserHostAddress + "<br>Host: " + Request.UserHostName %>

  • Python:
    • print "IP: " + cgi.os.environ["REMOTE_ADDR"] + "<br>Host: " + cgi.os.environ["REMOTE_HOST"]

  • Ruby:
    • print "IP: " + ENV["REMOTE_ADDR"] + "<br>Host: " + ENV["REMOTE_HOST"]

  • JSP:
    • <%= "IP: " + request.getRemoteAddr() + "<br>Host: " + request.getRemoteHost() %>

  • Java Servlet:
    • out.println("IP: " + request.getRemoteAddr() + "<br>Host: " + request.getRemoteHost());

    A common issue with the above calls is that in many cases host names may be returned as IP addresses or nothing at all. In some cases that is because no reverse record for a client's IP address is available. But if this issues occurs all the time, it could mean that reverse resolution is turned off. This is generally done for performance reason, to save on server resources.

    You can ask your hosting company to turn that service on, or you could configure reverse lookup yourself if you have access to the server configuration files. Here’s how reverse look up is switched on for Internet Information Server (IIS) and Apache.

  • IIS (execute at command line):
    • adsutil set w3svc/EnableReverseDNS TRUE

  • Apache (edit httpd.conf file):
    • HostnameLookups On

    By the way, if you ever wanted to run a simple reverse lookup on an IP address, here's a Reverse Whois tool for that job.

    Before I end this post, here's one more piece of information for those who might wonder where parameters like REMOTE_ADDR or REMOTE_HOST come from. Those are part of a collection of parameters known as environment variables that web servers are expected to make available to the scripts. Want the gory details? Read here.

    There you have it. If you can put any of the above scripts to use instead of using my JavaScript utility, I'd appreciate the bandwidth savings. And to those who continue to use my utilities, your trust and confidence are appreciated.

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