java - practica - ¿Cómo cierro un servidor UDP sin lanzar una excepción?

sockets con udp java

Question

Tengo un servidor que espera mensajes entrantes del cliente y usa UDP. Cuando trato de cerrar la conexión de Udp obtengo una 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;
}
}

private void btn_stopActionPerformed (java.awt.event.ActionEvent evt) {

 if ( serverStarted ){
Txt_Log.setText( Txt_Log.getText()+"/nServer has been stopped ...." ) ;
serverStarted = false ;
drop_DBconnection() ;
closeServer();
btn_start.setEnabled( true ) ;
btn_stop.setEnabled( false );
}
} 

Mi salida y stacktrace

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

¿Cómo cierro el servidor para que no se produzca ninguna excepción?

Answer 1

La excepción está cerrada porque cerró la excepción. Puede ver esta excepción y continuar en lugar de imprimirla. Esta es probablemente la mejor manera de manejar esto.