1 files changed, 118 insertions, 0 deletions
diff --git a/src/main/java/protocols/implementations/VSExternalTimeSyncProtocol.java b/src/main/java/protocols/implementations/VSExternalTimeSyncProtocol.java
new file mode 100644
index 0000000..f044861
--- /dev/null
+++ b/src/main/java/protocols/implementations/VSExternalTimeSyncProtocol.java
@@ -0,0 +1,118 @@
+package protocols.implementations;
+
+import core.VSMessage;
+import protocols.VSAbstractProtocol;
+
+/**
+ * The class VSExternalTimeSyncProtocol, an implementation of the external
+ * time synchronisation protocol.
+ *
+ * @author Paul C. Buetow
+ */
+public class VSExternalTimeSyncProtocol extends VSAbstractProtocol {
+    /** The request time. */
+    private long requestTime;
+
+    /** The server is waiting for response, if true. */
+    private boolean waitingForResponse;
+
+    /**
+     * Instantiates a new external time sync protocol object.
+     */
+    public VSExternalTimeSyncProtocol() {
+        super(VSAbstractProtocol.HAS_ON_CLIENT_START);
+        setClassname(getClass().toString());
+    }
+
+    /* (non-Javadoc)
+     * @see events.VSAbstractProtocol#onClientInit()
+     */
+    public void onClientInit() {
+    }
+
+    /* (non-Javadoc)
+     * @see protocols.VSAbstractProtocol#onClientReset()
+     */
+    public void onClientReset() {
+    }
+
+    /* (non-Javadoc)
+     * @see protocols.VSAbstractProtocol#onClientStart()
+     */
+    public void onClientStart() {
+        requestTime = process.getTime();
+        waitingForResponse = true;
+
+        /* Multicast message to all processes */
+        VSMessage message = new VSMessage();
+        message.setBoolean("isClientRequest", true);
+        sendMessage(message);
+    }
+
+    /* (non-Javadoc)
+     * @see protocols.VSAbstractProtocol#onClientRecv(core.VSMessage)
+     */
+    public void onClientRecv(VSMessage recvMessage) {
+        if (!recvMessage.getBoolean("isServerResponse"))
+            return;
+
+        if (waitingForResponse)
+            waitingForResponse = false;
+        else
+            return;
+
+        long recvTime = process.getTime();
+        long roundTripTime = recvTime - requestTime;
+        long serverTime = recvMessage.getLong("time");
+        long newTime = serverTime + (long) (roundTripTime / 2);
+
+        log("Server time: " + serverTime + "; RTT: " + roundTripTime + "; Old time: " + recvTime + "; New time: " + newTime + "; Offset: " + (newTime - recvTime));
+
+        process.setTime(newTime);
+    }
+
+    /* (non-Javadoc)
+     * @see protocols.VSAbstractProtocol#onClientSchedule()
+     */
+    public void onClientSchedule() {
+    }
+
+    /* (non-Javadoc)
+     * @see events.VSAbstractProtocol#onServerInit()
+     */
+    public void onServerInit() {
+    }
+
+    /* (non-Javadoc)
+     * @see protocols.VSAbstractProtocol#onServerReset()
+     */
+    public void onServerReset() {
+    }
+
+    /* (non-Javadoc)
+     * @see protocols.VSAbstractProtocol#onServerRecv(core.VSMessage)
+     */
+    public void onServerRecv(VSMessage recvMessage) {
+        if (!recvMessage.getBoolean("isClientRequest"))
+            return;
+
+        /* Multicast message to all processes */
+        VSMessage message = new VSMessage();
+        message.setLong("time", process.getTime());
+        message.setBoolean("isServerResponse", true);
+        sendMessage(message);
+    }
+
+    /* (non-Javadoc)
+     * @see protocols.VSAbstractProtocol#onServerSchedule()
+     */
+    public void onServerSchedule() {
+    }
+
+    /* (non-Javadoc)
+     * @see protocols.VSAbstractProtocol#toString()
+     */
+    public String toString() {
+        return super.toString();
+    }
+}