use port 0

Author: Vladimir Kotal

plugins/src/test/java/opengrok/auth/plugin/LdapServerTest.java

@@ -25,15 +25,13 @@
 import opengrok.auth.plugin.ldap.LdapServer;
 import org.junit.jupiter.api.Test;
 import org.mockito.Mockito;
-import org.opengrok.web.api.v1.controller.PortChecker;
 
 import java.io.IOException;
 import java.net.InetAddress;
 import java.net.ServerSocket;
 import java.net.Socket;
 import java.net.URISyntaxException;
 import java.net.UnknownHostException;
-import java.util.Random;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
@@ -81,26 +79,9 @@ public void testSetGetUsername() {
 
     @Test
     public void testIsReachable() throws IOException, InterruptedException, URISyntaxException {
-        final int testPortBase = 6336;    // It has to be > 1024 to avoid BindException due to permission denied.
-        final int randomRange = 49152;
-        int triesCount = 0;
-        final int MAX_PORT_TRIES = 20;
-        Random rand = new Random();
-        int testPort;
-        while (true) {
-            testPort = testPortBase + rand.nextInt(randomRange);
-            if (PortChecker.available(testPort)) {
-                break;
-            }
-            if (++triesCount > MAX_PORT_TRIES) {
-                throw new RuntimeException("Could not find an available port after " +
-                        MAX_PORT_TRIES + " tries");
-            }
-        }
-
         // Start simple TCP server on test port.
         InetAddress localhostAddr = InetAddress.getLocalHost();
-        ServerSocket serverSocket = new ServerSocket(testPort, 1, localhostAddr);
+        ServerSocket serverSocket = new ServerSocket(0, 1, localhostAddr);
         Thread thread = new Thread(() -> {
             try {
                 while (true) {
@@ -112,6 +93,7 @@ public void testIsReachable() throws IOException, InterruptedException, URISynta
             }
         });
 
+        int testPort = serverSocket.getLocalPort();
         thread.start();
         Socket socket = null;
         for (int i = 0; i < 3; i++) {