try{DatagramSocket udpSocket = new DatagramSocket(DEFAULT_PORT );} catch (Exception e){e.printStackTrace();}//java.net.BindException: bind failed: EADDRINUSE (Address already in use)

if(udpSocket==null){udpSocket = new DatagramSocket(null);udpSocket.setReuseAddress(true);udpSocket.bind(new InetSocketAddress(DEFAULT_PORT));}