feat: add JST calc class

[delesterandomselector/DelesteRandomSelector.git] / src / com / ranfa / lib / JST.java

diff --git a/src/com/ranfa/lib/JST.java b/src/com/ranfa/lib/JST.java
new file mode 100644 (file)
index 0000000..cd6f348
--- /dev/null
+++ b/src/com/ranfa/lib/JST.java
@@ -0,0 +1,70 @@
+package com.ranfa.lib;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.SocketException;
+import java.net.UnknownHostException;
+import java.util.Date;
+import java.util.Objects;
+
+import org.apache.commons.net.ntp.NTPUDPClient;
+import org.apache.commons.net.ntp.NtpV3Packet;
+import org.apache.commons.net.ntp.TimeInfo;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class JST {
+       
+       // Logger
+       private static final Logger LOG = LoggerFactory.getLogger(JST.class);
+       private static final String SERVER_NAME = "ntp.nict.jp";
+       
+       // private constructor
+       private JST() { /* do nothing */ }
+       
+       public static Date JSTNow() {
+               NTPUDPClient client = new NTPUDPClient();
+               InetAddress address = null;
+               try {
+                       address = InetAddress.getByName(SERVER_NAME);
+               } catch (UnknownHostException e) {
+                       // TODO 自動生成された catch ブロック
+                       e.printStackTrace();
+               }
+               try {
+                       client.open();
+               } catch (SocketException e) {
+                       // TODO 自動生成された catch ブロック
+                       e.printStackTrace();
+               }
+               TimeInfo info = null;
+               try {
+                       info = client.getTime(Objects.requireNonNull(address));
+               } catch (IOException e) {
+                       // TODO 自動生成された catch ブロック
+                       e.printStackTrace();
+               }
+               NtpV3Packet packet = Objects.requireNonNull(info).getMessage();
+               info.computeDetails();
+               LOG.debug("NTPClient: {}", client);
+               LOG.debug("NetAddress: {}", address);
+               LOG.debug("Time info: {}", info);
+               long t1 = packet.getOriginateTimeStamp().getTime();
+               long t2 = packet.getReceiveTimeStamp().getTime();
+               long t3 = packet.getTransmitTimeStamp().getTime();
+               long t4 = info.getReturnTime();
+               long CalculatedOffset = (t2 - t1 + t3 - t4) / 2;
+               long receiveOffset = info.getOffset();
+               long offset = ( CalculatedOffset + receiveOffset ) / 2;
+               Date date = new Date(System.currentTimeMillis() + offset);
+               LOG.debug("Client originate Time: {}", t1);
+               LOG.debug("Server Received request Time: {}", t2);
+               LOG.debug("Server Transmit response Time: {}", t3);
+               LOG.debug("Client Received response Time: {}", t4);
+               LOG.info("Estimated time offset: {}", CalculatedOffset);
+               LOG.info("received time offset: {}", receiveOffset);
+               LOG.info("estimated JST: {}", date);
+               LOG.info("Current client date: {}", new Date(System.currentTimeMillis()));
+               return date;
+       }
+}