Download Restlet Framework from: http://www.restlet.org/ (I took the zip-Archive for Java SE Edition)
It contains different Jar-Files. The most important one is org.restlet.jar. This is required to run the simple Server Example: http://wiki.restlet.org/docs_2.0/13-restlet/21-restlet/318-restlet/319-restlet.html
After you have this reference, you can start the server and open the URL:
There is a FireFox-plugin called RestClient (https://addons.mozilla.org/en-US/firefox/addon/restclient/?src=search) that also allows you to send http-Request and receive HTTP-Responses. The big advantage of the restclient is the possibility to view the HTTP header data (in the request and the response).