The question is: how do you configure the Java DB Network Server, like set its host and port number, for the server that NetBeans starts and stops for you?
The sad answer is: you can't from the IDE. There is a bug logged for this.
However, you can do this by editing the derby.properties file.
First, find out where your database directory is. In NetBeans 6, go to Tools->Java DB Database->Settings and see the value for Database Location
For NetBeans 5.5, go to the Preferences/Options panel for NetBeans, choose Advanced Options, and then under IDE Configuration->Server and External Tools Settings->Java DB Database look at Database Location.
Under that directory, edit derby.properties. The file should be there; if it's not, create it.
# Change host setting so you will accept connections from any host
# Change port number if you don't want to use the default of 1527
Then for both NetBeans 5.5 and NetBeans 6, do Tools->Java DB Database->Stop Server and then Start Server.
The new properties should now be applied.