| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.commons.net.examples.ntp; |
| |
| import org.apache.commons.net.ntp.NtpUtils; |
| import org.apache.commons.net.ntp.NtpV3Impl; |
| import org.apache.commons.net.ntp.NtpV3Packet; |
| import org.apache.commons.net.ntp.TimeStamp; |
| |
| import java.io.IOException; |
| import java.net.DatagramPacket; |
| import java.net.DatagramSocket; |
| |
| /** |
| * The SimpleNTPServer class is a UDP implementation of a server for the |
| * Network Time Protocol (NTP) version 3 as described in RFC 1305. |
| * It is a minimal NTP server that doesn't actually adjust the time but |
| * only responds to NTP datagram requests with response sent back to |
| * originating host with info filled out using the current clock time. |
| * To be used for debugging or testing. |
| * |
| * To prevent this from interfering with the actual NTP service it can be |
| * run from any local port. |
| */ |
| public class SimpleNTPServer implements Runnable { |
| |
| private int port; |
| |
| private volatile boolean running; |
| private boolean started; |
| |
| private DatagramSocket socket; |
| |
| /** |
| * Create SimpleNTPServer listening on default NTP port. |
| */ |
| public SimpleNTPServer() |
| { |
| this(NtpV3Packet.NTP_PORT); |
| } |
| |
| /** |
| * Create SimpleNTPServer. |
| * |
| * @param port the local port the server socket is bound to, or |
| * <code>zero</code> for a system selected free port. |
| * @throws IllegalArgumentException if port number less than 0 |
| */ |
| public SimpleNTPServer(int port) |
| { |
| if (port < 0) { |
| throw new IllegalArgumentException(); |
| } |
| this.port = port; |
| } |
| |
| public int getPort() |
| { |
| return port; |
| } |
| |
| /** |
| * Return state of whether time service is running. |
| * |
| * @return true if time service is running |
| */ |
| public boolean isRunning() |
| { |
| return running; |
| } |
| |
| /** |
| * Return state of whether time service is running. |
| * |
| * @return true if time service is running |
| */ |
| public boolean isStarted() |
| { |
| return started; |
| } |
| |
| /** |
| * Connect to server socket and listen for client connections. |
| * |
| * @throws IOException if an I/O error occurs when creating the socket. |
| */ |
| public void connect() throws IOException |
| { |
| if (socket == null) |
| { |
| socket = new DatagramSocket(port); |
| // port = 0 is bound to available free port |
| if (port == 0) { |
| port = socket.getLocalPort(); |
| } |
| System.out.println("Running NTP service on port " + port + "/UDP"); |
| } |
| } |
| |
| /** |
| * Start time service and provide time to client connections. |
| * |
| * @throws java.io.IOException if an I/O error occurs when creating the socket. |
| */ |
| public void start() throws IOException |
| { |
| if (socket == null) |
| { |
| connect(); |
| } |
| if (!started) |
| { |
| started = true; |
| new Thread(this).start(); |
| } |
| } |
| |
| /** |
| * main thread to service client connections. |
| */ |
| @Override |
| public void run() |
| { |
| running = true; |
| byte buffer[] = new byte[48]; |
| final DatagramPacket request = new DatagramPacket(buffer, buffer.length); |
| do { |
| try { |
| socket.receive(request); |
| final long rcvTime = System.currentTimeMillis(); |
| handlePacket(request, rcvTime); |
| } catch (IOException e) { |
| if (running) |
| { |
| e.printStackTrace(); |
| } |
| // otherwise socket thrown exception during shutdown |
| } |
| } while (running); |
| } |
| |
| /** |
| * Handle incoming packet. If NTP packet is client-mode then respond |
| * to that host with a NTP response packet otherwise ignore. |
| * |
| * @param request incoming DatagramPacket |
| * @param rcvTime time packet received |
| * |
| * @throws IOException if an I/O error occurs. |
| */ |
| protected void handlePacket(DatagramPacket request, long rcvTime) throws IOException |
| { |
| NtpV3Packet message = new NtpV3Impl(); |
| message.setDatagramPacket(request); |
| System.out.printf("NTP packet from %s mode=%s%n", request.getAddress().getHostAddress(), |
| NtpUtils.getModeName(message.getMode())); |
| if (message.getMode() == NtpV3Packet.MODE_CLIENT) { |
| NtpV3Packet response = new NtpV3Impl(); |
| |
| response.setStratum(1); |
| response.setMode(NtpV3Packet.MODE_SERVER); |
| response.setVersion(NtpV3Packet.VERSION_3); |
| response.setPrecision(-20); |
| response.setPoll(0); |
| response.setRootDelay(62); |
| response.setRootDispersion((int) (16.51 * 65.536)); |
| |
| // originate time as defined in RFC-1305 (t1) |
| response.setOriginateTimeStamp(message.getTransmitTimeStamp()); |
| // Receive Time is time request received by server (t2) |
| response.setReceiveTimeStamp(TimeStamp.getNtpTime(rcvTime)); |
| response.setReferenceTime(response.getReceiveTimeStamp()); |
| response.setReferenceId(0x4C434C00); // LCL (Undisciplined Local Clock) |
| |
| // Transmit time is time reply sent by server (t3) |
| response.setTransmitTime(TimeStamp.getNtpTime(System.currentTimeMillis())); |
| |
| DatagramPacket dp = response.getDatagramPacket(); |
| dp.setPort(request.getPort()); |
| dp.setAddress(request.getAddress()); |
| socket.send(dp); |
| } |
| // otherwise if received packet is other than CLIENT mode then ignore it |
| } |
| |
| /** |
| * Close server socket and stop listening. |
| */ |
| public void stop() |
| { |
| running = false; |
| if (socket != null) |
| { |
| socket.close(); // force closing of the socket |
| socket = null; |
| } |
| started = false; |
| } |
| |
| public static void main(String[] args) |
| { |
| int port = NtpV3Packet.NTP_PORT; |
| if (args.length != 0) |
| { |
| try { |
| port = Integer.parseInt(args[0]); |
| } catch (NumberFormatException nfe) { |
| nfe.printStackTrace(); |
| } |
| } |
| SimpleNTPServer timeServer = new SimpleNTPServer(port); |
| try { |
| timeServer.start(); |
| } catch (IOException e) { |
| e.printStackTrace(); |
| } |
| } |
| |
| } |