How do I close a UDP server without throwing an exception?

[phpuser123]

I have a server that waits for incoming client messages and uses UDP. When I try to close the Udp connection I get an IOException..

 
public void run(){
 
    String user_message = null;
 
    try {
            connection = startServer();
            System.out.println("Server started");
            while ((true) && (serverStarted) ){
 
                    try {
 
 
                            user_message = receiveMessage();
                            check_query( user_message , "," );
 
                    } catch ( IOException ex ) {
                            System.out.println("Error1 "+ex.getMessage());
                            setError( "Error establishing connection " ) ;
                            Txt_Log.setText(Txt_Log.getText() + "\n Error establishing connection0") ;
                            break;
                        }
                }
            System.out.println("Server is stopped.....");
        }
    catch ( SocketException ex ) {
            System.out.println("Error2 "+ex.getMessage());
            setError("Error establishing connection ") ;
            Txt_Log.setText(Txt_Log.getText() + "\n Error establishing connection1") ;
 
       }
    catch( NullPointerException ex){
            System.out.println("Error3 "+ex.getMessage());
            ex.printStackTrace();
            setError("Error Null Pointer ") ;
            Txt_Log.setText(Txt_Log.getText() + "\n Error :"+ex.getMessage()) ;
    }
}
 
 
 
 
 
/*
 * Method starts server datagram to bind to port
 */
 
public DatagramSocket startServer() throws SocketException{
 
            return new DatagramSocket(10000);
}
 
 
 
 
/*
 * Method stops server so that server is not able to receive client requests
 */
 
public void closeServer(){
 
        if (connection != null){
                //connection.disconnect();
                connection.close();
                //connection = null;
 
        }
}
 
 
 
/*
 * Method sends message via datagram to client
 */
 
private void sendMessage( String message ) throws IOException{
 
        byte[] message_byte = message.getBytes();
        packet_send = new DatagramPacket( message_byte , message_byte.length , packet_receive.getAddress() , packet_receive.getPort() );
        connection.send( packet_send );
}
 
 
 
 
/*
 * Method receives messages from clients
 */
private String receiveMessage() throws IOException,NullPointerException{
    if (connection!=null){
        byte[] buf = new byte[256];
        packet_receive = new DatagramPacket( buf , buf.length ) ;
        connection.receive( packet_receive ) ;
        return getString( packet_receive );
    }
    throw new NullPointerException("Connection cannot be null");
}
 
 
 
/*
 * Method retrieves data from packet and converts to string
 */
 
private String getString(DatagramPacket packet){
 
        String string = new String ( packet.getData() , 0 , packet.getLength()).trim();
        return string;
}
 
private void drop_DBconnection(){ if (DB_connection!=null){ try{ DB_connection.close(); //DB_connection = null;
 
            }
        catch(SQLException e){
 
                Txt_Log.setText("Server connection Error...");
                setError("Cannot close database connection");
            }
 
        }
}
 
public void closeServer(){
 
        if (connection != null){
                //connection.disconnect();
                connection.close();
                //connection = null;
 
        }
}
 
 
 

My output and stacktrace

Server started Server is started..... Error1 socket closed Server is stopped..... java.net.SocketException: socket closed at java.net.PlainDatagramSocketImpl.receive0(Native Method) at java.net.PlainDatagramSocketImpl.receive(PlainData gramSocketImpl.java:136) at java.net.DatagramSocket.receive(DatagramSocket.jav a:712) at server.Server.receiveMessage(Server.java:608) at server.Server.run(Server.java:528) at java.lang.Thread.run(Thread.java:619)

How do I close the server so that no exception is thrown?

[horace1]

where do you call closeServer()
I suggest you need to terminate the run() method when the server is closed, e.g. possibly some test here to ensure the server is still running ?

       while ((true) && (serverStarted) ){
 

[Dheeraj Joshi]

I am not sure how closeServer methos is working in your project.
Better to add some intelligence to closeserver method and what it returns.

Depending on the output you can continue your operation.

Regards
Dheeraj Joshi