That depends on your network setup. In company networks, inbound traffic is generally restricted to one particular subnet, of which your machine is most likely not part. The network admin would also need to set up an external IP address for your machine. But in all likelihood, he's going to do neither of those things for security reasons.
If you're directly connected to the internet (e.g. through DSL) you'll just have to open your firewall on whichever port the WS is listening, and tell the other side what IP address you have. Note that the address can change if you have a dynamic IP address. I would advise against opening up your system in this way.
Alternatively, you can put it on a Java-enabled web host, which can be had starting at around USD 5 per month. [ January 07, 2008: Message edited by: Ulf Dittmer ]