Is there a configuration setting I need to modify somewhere for this to work?
Check you server configuration.
If the address var is set to 127.0.0.1 you wont be able to get to it via other addresses.
Change this to your IP address.
Should be in conf/server.xml.
Also it may be that your app is restricted to certain hosts.
Check point 10 in this link: http://oreilly.com/pub/a/java/archive/tomcat-tips.html?page=2
Hope this helps you.
I had the same issue and tomcat was returning a status 400. This was due to the fact that my tomcat installation did not have the following directory: tomcat\webapps\ROOT
Inside this directory is the index.html that is being looked for when http://localhost:8081 is requested.
Just something else to check.