How do I use the core net library in another library?

Hi, I'm trying to create a library that uses the core net module, but I'm not sure how to do it properly.

This is the setup I have:

  • I'm using the official template inside eclipse
  • As recommended in the file, I have a libs folder, with core.js and net.jar (taken from /Applications/
  • Updated classpath.local.include in with net.jar
  • Added libs/net.jar it to the build path as an external jar file

The ant build builds fine, but when I try to run it in processing, I get the error ClassNotFoundException:, unless I include import in my sketch.

I've also noticed that the arduino library does a similar thing with requiring the core serial module (, and they also explicitly include import processing.serial.*; in their examples. Is this the proper way of doing it?

I also dug around a bit and the arduino jar file contains a Arduino$SerialProxy.class file in the [Processing lib]/Arduino/cc/arduino folder, which I can't see anywhere in the source code. Is this something I need too?

Another hack to the solution was to put a duplicate of net.jar inside the lib (note: not libs) folder, and the build script builds correctly, and the processing sketch runs it without error, but there are conflicts with the core processing library.

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