From 3e25d539e20e43892bb9a92b39d93915927300aa Mon Sep 17 00:00:00 2001
From: Oliver Lietz <info@oliverlietz.de>
Date: Sun, 13 Aug 2023 17:25:54 +0200
Subject: [PATCH] #1020 Regression - failure when starting two Karaf containers
 [PAXEXAM-940]

use free port finding method from Sling's TestSupport
---
 .../internal/KarafTestContainer.java          | 50 +++++++++----------
 1 file changed, 24 insertions(+), 26 deletions(-)

diff --git a/containers/pax-exam-container-karaf/src/main/java/org/ops4j/pax/exam/karaf/container/internal/KarafTestContainer.java b/containers/pax-exam-container-karaf/src/main/java/org/ops4j/pax/exam/karaf/container/internal/KarafTestContainer.java
index 54b0ec727..8a293bbc0 100644
--- a/containers/pax-exam-container-karaf/src/main/java/org/ops4j/pax/exam/karaf/container/internal/KarafTestContainer.java
+++ b/containers/pax-exam-container-karaf/src/main/java/org/ops4j/pax/exam/karaf/container/internal/KarafTestContainer.java
@@ -31,17 +31,25 @@
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
-import java.net.BindException;
 import java.net.InetAddress;
+import java.net.ServerSocket;
 import java.net.URL;
 import java.rmi.NoSuchObjectException;
-import java.rmi.RemoteException;
 import java.rmi.registry.LocateRegistry;
 import java.rmi.registry.Registry;
 import java.rmi.server.UnicastRemoteObject;
-import java.text.DateFormat;
 import java.text.SimpleDateFormat;
-import java.util.*;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Date;
+import java.util.HashMap;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Properties;
+import java.util.Queue;
+import java.util.Set;
+import java.util.UUID;
 
 import org.apache.commons.io.FileUtils;
 import org.apache.commons.io.filefilter.WildcardFileFilter;
@@ -121,6 +129,15 @@ public KarafTestContainer(ExamSystem system,
         this.runner = runner;
     }
 
+    @SuppressWarnings({"java:S112", "checkstyle:IllegalCatch"})
+    private static int findFreePort() {
+        try (ServerSocket serverSocket = new ServerSocket(0)) {
+            return serverSocket.getLocalPort();
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+
     @Override
     public synchronized TestContainer start() {
         try {
@@ -131,7 +148,9 @@ public synchronized TestContainer start() {
             //registry.selectGracefully();
 			String host = InetAddress.getLoopbackAddress().getHostAddress();
 			System.setProperty("java.rmi.server.hostname", host);
-			int port = openRegistryOnFreePort(host, 21000, 21099);
+            int port = findFreePort();
+            LOGGER.info("Creating RMI registry server on {}:{}", host, port);
+            registry = LocateRegistry.createRegistry(port);
 
             ExamSystem subsystem = system
                 .fork(options(
@@ -221,27 +240,6 @@ private void restoreConfigFiles() {
         }
     }
 
-	private int openRegistryOnFreePort(String host, int minPort, int maxPort) throws RemoteException {
-		for (int port = minPort; port <= maxPort; port++) {
-			try {
-				LOGGER.trace("Creating RMI registry server on {}:{}", host, port);
-				registry = LocateRegistry.createRegistry(port);
-				LOGGER.info("Created RMI registry server on {}:{}", host, port);
-				return port;
-			} catch (RemoteException ex) {
-				if (ex.detail instanceof BindException) {
-					LOGGER.trace("Tried to open RMI registry on {}: {} but failed.", host, port, ex);
-					if (port >= maxPort) {
-						throw ex;
-					}
-				} else {
-					throw ex;
-				}
-			}
-		}
-		throw new IllegalStateException("Could not open RMI registry");
-	}
-
     private boolean shouldInjectJUnitBundles(ExamSystem _system) {
         Option[] options = _system.getOptions(OverrideJUnitBundlesOption.class);
         LOGGER.info("Found {} options when requesting OverrideJUnitBundlesOption.class", options.length);