Simple TCP utility failing right out the gate

I'm trying to set up TCP communications between two machines, but for now (in the initial/testing phase) am using localhost.

Can anybody see why I'm getting these msgs in the Console (all I'm doing is running the app, not even pressing the button:

java.net.ConnectException: Connection refused: connect
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(Unknown Source)
at java.net.PlainSocketImpl.connectToAddress(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.<init>(Unknown Source)
at java.net.Socket.<init>(Unknown Source)
at com.jcp.tds.RTTCPSortSimMain.setUpNetworking(RTTCP SortSimMain.java:104)
at com.jcp.tds.RTTCPSortSimMain.go(RTTCPSortSimMain.j ava:91)
at com.jcp.tds.RTTCPSortSimMain.main(RTTCPSortSimMain .java:34)
Exception in thread "Thread-2" java.lang.NullPointerException
at com.jcp.tds.RTTCPSortSimMain$IncomingReader.run(RT TCPSortSimMain.java:138)
at java.lang.Thread.run(Unknown Source)

with the following code (which is basically ripped straight from "Head First Java"):

Code Java:

---

public class RTTCPSortSimMain {
 
...
    BufferedReader reader;
    PrintWriter writer;
    Socket sock;
 
	public static void main(String[] args) {
		new RTTCPSortSimMain().go();
	}
 
	public void go() {
... (GUI code)       
        JButton sendButton = new JButton("Send and Receive");
        sendButton.addActionListener(new SendButtonListener());
 
        tfHost = new JTextField(16); 
        tfHost.setText("127.0.0.1");
        tfPort = new JTextField(4);
        tfPort.setText("4211"); 
 
... (more GUI code)
 
        setUpNetworking();
 
        Thread readerThread = new Thread(new IncomingReader());
        readerThread.start();
 
... (more GUI code)
 
    }
 
        private void setUpNetworking() {
        try {
            // for testing (localhost)
 	sock = new Socket("127.0.0.1", 5000);
            InputStreamReader streamReader = new InputStreamReader(sock.getInputStream());
            reader = new BufferedReader(streamReader);
            writer = new PrintWriter(sock.getOutputStream());
            System.out.println("networking established");
        }
        catch(IOException ex)
        {
            ex.printStackTrace();
        }
    }
 
        public class SendButtonListener implements ActionListener {
        @Override
		public void actionPerformed(ActionEvent ev) {
            try {
                writer.println(outgoing.getText());
                writer.flush();
 
            }
            catch (Exception ex) {
                ex.printStackTrace();
            }
            outgoing.setText("");
            outgoing.requestFocus();
        }
    }
 
        class IncomingReader implements Runnable {
        @Override
		public void run() {
            String message;
            try {
                while ((message = reader.readLine()) != null) {
                    System.out.println("client read " + message);
                    incoming.append(message + "\n");
                }
            } catch (IOException ex)
            {
                ex.printStackTrace();
            }
        }
    }
 
}

---

?

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