You are right that each bundle is loaded by it's own classloader, the usual class loading structure is not used in OSGi. Any class you want to use (with a very small set of exceptions) must be made avaliable with either an import-package or an import-bundle.
The first thing I would check is that your bundle is importing the 'javax.net' package. You don't need to worry about exporting it from anywhere as it is avaliable from the system bundle (bundle 0).
Spring Insight and CloudFoundry