Find free hub port to support multiple local grids in common environm…

…ent.

client/src/main/java/com/paypal/selion/internal/platform/grid/LocalHub.java

@@ -15,7 +15,15 @@
 
 package com.paypal.selion.internal.platform.grid;
 
+import java.io.IOException;
+import java.net.BindException;
+import java.net.ConnectException;
+import java.net.InetSocketAddress;
+import java.net.Socket;
+import java.net.UnknownHostException;
+
 import org.openqa.selenium.net.NetworkUtils;
+import org.openqa.selenium.net.PortProber;
 
 import com.paypal.selion.configuration.Config;
 import com.paypal.selion.configuration.Config.ConfigProperty;
@@ -42,9 +50,13 @@ static synchronized LocalServerComponent getSingleton() {
     synchronized LocalHub getLocalServerComponent() {
         if (instance == null) {
             instance = new LocalHub();
+            instance.setHost(new NetworkUtils().getNonLoopbackAddressOfThisMachine());
 
-            instance.setHost(new NetworkUtils().getIpOfLoopBackIp4());
-            instance.setPort(Integer.parseInt(Config.getConfigProperty(ConfigProperty.SELENIUM_PORT)));
+            int configHubPort = Integer.parseInt(Config.getConfigProperty(ConfigProperty.SELENIUM_PORT));
+            // Choose another free port when config port is not available.
+            int hubPort = LocalHub.pollPort(configHubPort) ? configHubPort : PortProber.findFreePort();
+            Config.setConfigProperty(ConfigProperty.SELENIUM_PORT, Integer.toString(hubPort));
+            instance.setPort(hubPort);
 
             LauncherOptions launcherOptions = new LauncherOptionsImpl()
                     .setFileDownloadCheckTimeStampOnInvocation(false).setFileDownloadCleanupOnInvocation(false);
@@ -75,4 +87,37 @@ public void shutdown() {
         super.shutdown();
         LOGGER.exiting();
     }
+
+
+    /**
+     * Polls port on localhost for its availability for 15 seconds.
+     */
+    private static boolean pollPort(int port) {
+        long end = System.currentTimeMillis() + 15000;
+        while (System.currentTimeMillis() < end) {
+            Socket socket = new Socket();
+            try {
+                socket.setReuseAddress(false);
+                socket.bind(new InetSocketAddress("localhost", port));
+                socket.close();
+                return true;
+            } catch (ConnectException | BindException e) {
+                // Ignore this
+            } catch (UnknownHostException e) {
+                throw new RuntimeException(e);
+            } catch (IOException e) {
+                throw new RuntimeException(e);
+            } finally {
+                if ((socket != null) && !socket.isClosed()) {
+                    try {
+                        socket.close();
+                    } catch (IOException e) {
+                        LOGGER.info("Error closing socket.");
+                    }
+                }
+            }
+        }
+
+        return false;
+      }
 }