Question

Getting these errors in some java code

http://tutorials.jenkov.com/java-multithreaded-servers/multithreaded-server.html

Exception in thread "Thread-0" java.lang.RuntimeException: Cannot open port 8080
at servers.MultiThreadedServer.openServerSocket(MultiThreadedServer.java:61)
at servers.MultiThreadedServer.run(MultiThreadedServer.java:22)
at java.lang.Thread.run(Thread.java:679)
Caused by: java.net.BindException: Address already in use
at java.net.PlainSocketImpl.socketBind(Native Method)
at java.net.AbstractPlainSocketImpl.bind(AbstractPlainSocketImpl.java:353)
at java.net.ServerSocket.bind(ServerSocket.java:336)
at java.net.ServerSocket.<init>(ServerSocket.java:202)
at java.net.ServerSocket.<init>(ServerSocket.java:114)
at servers.MultiThreadedServer.openServerSocket(MultiThreadedServer.java:59)
... 2 more
     Exception in thread "main" Stopping Server
  java.lang.NullPointerException
at servers.MultiThreadedServer.stop(MultiThreadedServer.java:51)
at servers.Dispatch.main(Dispatch.java:18)

I made these files

WorkerRunnable.java

package servers;

import java.io.InputStream;
import java.io.OutputStream;
import java.io.IOException;
import java.net.Socket;

/**

*/
public class WorkerRunnable implements Runnable{

protected Socket clientSocket = null;
protected String serverText   = null;

public WorkerRunnable(Socket clientSocket, String serverText) {
    this.clientSocket = clientSocket;
    this.serverText   = serverText;
}

public void run() {
    try {
        InputStream input  = clientSocket.getInputStream();
        OutputStream output = clientSocket.getOutputStream();
        long time = System.currentTimeMillis();
        output.write(("HTTP/1.1 200 OK\n\nWorkerRunnable: " +
                this.serverText + " - " +
                time +
                "").getBytes());
        output.close();
        input.close();
        System.out.println("Request processed: " + time);
    } catch (IOException e) {
        //report exception somewhere.
        e.printStackTrace();
    }
  }
 }

MultiThreadedServer.java

package servers;

import java.net.ServerSocket;
import java.net.Socket;
import java.io.IOException;

public class MultiThreadedServer implements Runnable{

protected int          serverPort   = 8080;
protected ServerSocket serverSocket = null;
protected boolean      isStopped    = false;
protected Thread       runningThread= null;

public MultiThreadedServer(int port){
    this.serverPort = port;
}

public void run(){
    synchronized(this){
        this.runningThread = Thread.currentThread();
    }
    openServerSocket();
    while(! isStopped()){
        Socket clientSocket = null;
        try {
            clientSocket = this.serverSocket.accept();
        } catch (IOException e) {
            if(isStopped()) {
                System.out.println("Server Stopped.") ;
                return;
            }
            throw new RuntimeException(
                "Error accepting client connection", e);
        }
        new Thread(
            new WorkerRunnable(
                clientSocket, "Multithreaded Server")
        ).start();
    }
    System.out.println("Server Stopped.") ;
}


private synchronized boolean isStopped() {
    return this.isStopped;
}

public synchronized void stop(){
    this.isStopped = true;
    try {
        this.serverSocket.close();
    } catch (IOException e) {
        throw new RuntimeException("Error closing server", e);
    }
}

private void openServerSocket() {
    try {
        this.serverSocket = new ServerSocket(this.serverPort);
    } catch (IOException e) {
        throw new RuntimeException("Cannot open port 8080", e);
    }
}

}

Dispatch.java

 package servers;

 public class Dispatch {

/**
 * @param args
 */
public static void main(String[] args) {
    MultiThreadedServer server = new MultiThreadedServer(9000);
    new Thread(server).start();

    try {
        Thread.sleep(20 * 1000);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    System.out.println("Stopping Server");
    server.stop();

}

}

Answer 1

Your machine’s port 8080 being used by other program

Terminate program that use port 8080

You can find out the program via following command (Windows):

netstat -o -n -a | findstr 0.0:8080

Example output:

TCP 0.0.0.0:8080 0.0.0.0:0 LISTENING 8704

Then you can find the program using PID 8704 using Task Manager and terminate it.

Refer here in more details.

Use other port

You can change the

protected int serverPort   = 8080;

to

protected int serverPort   = 8888;

Or

MultiThreadedServer server = new MultiThreadedServer(8888);

So it is use port 8888 instead of 8080.