InetAddress.isReachable is reported reliable on mac and recent java versions

Refactored NetUtils.isReachable to two functions:
isReachableByEcho and isPortOpen
If the first one will fail, the second one will be used

Author: Federico Fissore

arduino-core/src/cc/arduino/packages/discoverers/NetworkDiscovery.java

@@ -75,10 +75,7 @@ public List<BoardPort> discovery() {
           ports.add(0, 22);
         }
 
-        boolean reachable = false;
-        for (Integer port : ports) {
-          reachable = reachable || NetUtils.isReachable(inetAddress, port);
-        }
+        boolean reachable = NetUtils.isReachable(inetAddress, ports);
         if (!reachable) {
           boardPortIterator.remove();
         }

arduino-core/src/processing/app/helpers/NetUtils.java

@@ -4,10 +4,37 @@
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.Socket;
+import java.util.Arrays;
+import java.util.List;
 
 public abstract class NetUtils {
 
+  private static boolean isReachableByEcho(InetAddress address) {
+    try {
+      return address.isReachable(100);
+    } catch (IOException e) {
+      return false;
+    }
+  }
+
   public static boolean isReachable(InetAddress address, int port) {
+    return isReachable(address, Arrays.asList(port));
+  }
+
+  public static boolean isReachable(InetAddress address, List<Integer> ports) {
+    if (isReachableByEcho(address)) {
+      return true;
+    }
+
+    boolean reachable = false;
+    for (Integer port : ports) {
+      reachable = reachable || isPortOpen(address, port);
+    }
+
+    return reachable;
+  }
+
+  private static boolean isPortOpen(InetAddress address, int port) {
     Socket socket = null;
     try {
       socket = new Socket();