Server Pinger Multithreading Issues

Question

I am making a GUI server pinger application, and have multithreaded each port on a list so that each port is check by a separate thread. The problem I am having is that sometimes the port is check twice (according to the output). Here is my code: Class PingThread:

package serverpinger;

import java.io.IOException;
import java.net.InetAddress;
import java.rmi.UnknownHostException;

public class PingThread extends Thread{
    TextFieldOutput output;
    private String IPAddress;
    private int portNo;
    public PingThread(String IPAdress, int portNo,TextFieldOutput output){
        this.IPAddress=IPAdress;
        this.portNo=portNo;
        this.output=output;
    }
    
    @Override
    public void run(){
        String result="";
        try{
            InetAddress address=InetAddress.getByName(IPAddress);
            if(address.isReachable(portNo)){
                result+="Reachable at: IPAddress: "+IPAddress+" Port: "+portNo+"\n";
            }
            else{
                result+="Unreachable at: IPAddress: "+IPAddress+" Port: "+portNo+"\n";
            }
        }
        catch(UnknownHostException uhe){
            result+="UnknownHostException for: IPAddress: "+IPAddress+" Port: "+portNo+"\n";
        }
        catch(IOException ioe){
            result+="IOException for: IPAddress: "+IPAddress+" Port: "+portNo+"\n";
        }
        output.setText(output.getText()+result);
    }
}

Class ButtonRun:

package serverpinger;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Scanner;
import javax.swing.JButton;

public class ButtonRun extends JButton{
    TextFieldInput input;
    TextFieldOutput output;
    public ButtonRun(TextFieldInput input,TextFieldOutput output){
        super("Run");
        
        addActionListener(new ActionListener() { 
            @Override
            public void actionPerformed(ActionEvent e) { 
                Scanner scanner=new Scanner(input.getText());
                input.selectAll();
                input.replaceSelection("");
                String IPAddress=scanner.next();
                
                while(scanner.hasNext()){
                    String port=scanner.next();
                    
                    if(port.contains("-")){
                        for(int portNo=Integer.parseInt(port.substring(0,4));
                                portNo<=Integer.parseInt(port.substring(5,9));
                                portNo++){
                            PingThread ping=new PingThread(IPAddress,portNo,output);
                            ping.start();
                        }
                    }
                    else{
                        PingThread ping=new PingThread(IPAddress,Integer.parseInt(port),output);
                        ping.start();
                    }
                }
            } 
        });
    }
}

The rest of the classes are just subclasses of various JComponents, tailored to fit the application and make it look pretty.

Also, on occasion, the output will yield a line with random numbers (i.e. 7, 677) or a line that has the first two characters taken off (i.e. achable at IPAddress: example Port: example).

I don't know the source of any of the three glitches except that I am likely doing something wrong with the multithreading.

EDIT: I tried putting it on the Event Dispatch Thread and it still does not work, reproducing the same glitches. Here is the PingThread class now:

package serverpinger;

import java.io.IOException;
import java.net.InetAddress;
import java.rmi.UnknownHostException;
import javax.swing.SwingWorker;

public class PingThread extends SwingWorker{
    TextFieldOutput output;
    private String IPAddress;
    private int portNo;
    public PingThread(String IPAdress, int portNo,TextFieldOutput output){
        this.IPAddress=IPAdress;
        this.portNo=portNo;
        this.output=output;
    }
    
    @Override
    public PingThread doInBackground(){
        String result="";
        try{
            InetAddress address=InetAddress.getByName(IPAddress);
            if(address.isReachable(portNo)){
                result+="Reachable at: IPAddress: "+IPAddress+" Port: "+portNo+"\n";
            }
            else{
                result+="Unreachable at: IPAddress: "+IPAddress+" Port: "+portNo+"\n";
            }
        }
        catch(UnknownHostException uhe){
            result+="UnknownHostException for: IPAddress: "+IPAddress+" Port: "+portNo+"\n";
        }
        catch(IOException ioe){
            result+="IOException for: IPAddress: "+IPAddress+" Port: "+portNo+"\n";
        }
        output.setText(output.getText()+result);
        return this;
    }
}