The package "processing.net" does not exist.  You might be missing a library.

As of release 1.0, libraries must be installed in a folder named 'libraries' inside the 'sketchbook' folder.

1. // file: ReaderThread.java
2. import processing.core.*;
3. import processing.net.*;
4. 
   
5. class ReaderThread implements Runnable {
6.     PApplet _parent;
7.     Listener _listener;
8.     Thread _thread;
9.     Client _client;
11.     static String HOST = "localhost";
12.     static int PORT = 5204;
13.     static char EOL = '\n';
14. 
    
15.     ReaderThread(PApplet parent, Listener listener) {
16.         _parent = parent;
17.         _listener = listener;
18.         _client = new Client(_parent, HOST, PORT);
19.         new Thread(this).start();
20.     }
21. ...