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From GitBox <...@apache.org>
Subject [GitHub] [incubator-plc4x] JulianFeinauer commented on a change in pull request #57: Feature/plc4 x 108 ping method
Date Fri, 29 Mar 2019 10:38:42 GMT
JulianFeinauer commented on a change in pull request #57: Feature/plc4 x 108 ping method
URL: https://github.com/apache/incubator-plc4x/pull/57#discussion_r270356482
 
 

 ##########
 File path: plc4j/protocols/driver-bases/base/src/main/java/org/apache/plc4x/java/base/connection/AbstractPlcConnection.java
 ##########
 @@ -57,6 +67,51 @@ public boolean canSubscribe() {
         return false;
     }
 
+    /**
+     * The default implementation uses the {@link #ping(int)} method.
+     * Drivers that want to implement a more specific version have to overide it.
+     */
+    @Override
+    public boolean isConnected() {
+        return ping(PING_TIMEOUT_MS);
+    }
+
+    /**
+     * Method that sends a test-request or ping to the PLC to check if the PLC is still there.
+     * In most cases this method should only be used from the {@link #isConnected()} method.
+     * This method can only be used if ghe {@link #getInetSocketAddress()} returns a Socket
Adress.
+     * Otherwise it throws a {@link NotImplementedException} to inform the user about that.
+     */
+    protected boolean ping(int timeout) {
+        Optional<InetSocketAddress> address = getInetSocketAddress();
+        if (!address.isPresent()) {
+            throw new NotImplementedException("Tries to check the connection with ping, "
+
+                "but no Socket Address is given!");
+        }
+        Socket s = null;
+        try {
+            s = new Socket();
+            s.connect(address.get(), timeout);
+            return true;
+        } catch (Exception e) {
+            LOGGER.debug("Unable to ping PLC", e);
+            return false;
+        } finally {
+            if (s != null) {
+                try {
+                    s.close();
+                } catch (Exception e) {
+                }
+            }
+        }
+    }
+
+    /**
+     * Strategy Pattern method for the {@link #ping(int)} method.
+     * If a driver has no Inet Socket adress, it has to return an Empty Optional, never null.
 
 Review comment:
   Indeed this is redundandent. But I'm a bit "conservative" with these Java 8 features as
there may be people not so used to them so I think its okay to make it *really* clear :)
   Better safe than sorry.

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