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
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@@ -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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