WebMatrix/IIS Express only works with Opera!
First let's see if it is actually running off port 55555. Try:
netstat -a | find "LISTENING"
You should see an entry on port 55555. If it is in fact running your service. In any other case, open a browser and try http://127.0.0.1:55555 instead of using localhost. Most of the time this isn't an issue, but it's best to cover our bases.
If that still doesn't work, my suspicion is a misconfiguration of the service itself. Another option, if you can't get this to work is to set up an Apache web server instead of using IIS.