NetworkDiscovery: InetAddress.isReachable() is unreliable, let's open a socket

Author: Federico Fissore

app/src/cc/arduino/packages/discoverers/NetworkDiscovery.java

@@ -4,13 +4,13 @@
 import cc.arduino.packages.Discovery;
 import cc.arduino.packages.discoverers.network.NetworkChecker;
 import processing.app.Base;
+import processing.app.helpers.NetUtils;
 import processing.app.helpers.PreferencesMap;
 import processing.app.zeroconf.jmdns.ArduinoDNSTaskStarter;
 
 import javax.jmdns.*;
 import javax.jmdns.impl.DNSTaskStarter;
 import java.io.IOException;
-import java.net.Inet4Address;
 import java.net.InetAddress;
 import java.net.UnknownHostException;
 import java.util.*;
@@ -33,14 +33,11 @@ public List<BoardPort> discovery() {
     Iterator<BoardPort> iterator = ports.iterator();
     while (iterator.hasNext()) {
       try {
-        InetAddress address = Inet4Address.getByName(iterator.next().getAddress());
-        if (!address.isReachable(100)) {
+        if (!NetUtils.isReachable(InetAddress.getByName(iterator.next().getAddress()))) {
           iterator.remove();
         }
       } catch (UnknownHostException e) {
         iterator.remove();
-      } catch (IOException e) {
-        iterator.remove();
       }
     }
     return ports;

app/src/processing/app/helpers/NetUtils.java

@@ -0,0 +1,28 @@
+package processing.app.helpers;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.Socket;
+
+public abstract class NetUtils {
+
+  public static boolean isReachable(InetAddress address) {
+    Socket socket = null;
+    try {
+      socket = new Socket();
+      socket.connect(new InetSocketAddress(address, 80), 100);
+      return true;
+    } catch (IOException e) {
+      return false;
+    } finally {
+      if (socket != null) {
+        try {
+          socket.close();
+        } catch (IOException e) {
+          // noop
+        }
+      }
+    }
+  }
+}