What you need is the Application URL node from the HTTP palette. This gives your code access to the full url of the page containing your deployed applicaiton. Your users can then use the ? syntax to provide additional information in the url. For example if you application is deployed at http://yourserver/webapp.html, they could add an IP address as http://yourserver/webapp.html?130.164.1.1. If you have multiple pieces of information, a syntax like the following is typically used: http://yourserver/webapp.html?ip=130.164.1.1&port=8080.
This node will return empty strings when run in the development environment, so you probably want to put a check in your code that will return a default string if the output is empty. This allows you to still run the code in the editor while still exercising your URL parsing code.