tests: refactored blackbox test for LWM2M test client (UDP DatagramSocket instead TCP ServerSocket), ensure UDP socket is available before and after LWM2M client start stop

msa/black-box-tests/src/test/java/org/thingsboard/server/msa/PortFinder.java

@@ -0,0 +1,42 @@
+/**
+ * Copyright © 2016-2026 The Thingsboard Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.thingsboard.server.msa;
+
+import lombok.extern.slf4j.Slf4j;
+
+import java.io.IOException;
+import java.net.DatagramSocket;
+import java.net.SocketException;
+
+@Slf4j
+public class PortFinder {
+    public static int findAvailableUdpPort() {
+        try (DatagramSocket socket = new DatagramSocket(0)) {
+            return socket.getLocalPort();
+        } catch (SocketException e) {
+            throw new IllegalStateException("No available UDP ports found", e);
+        }
+    }
+
+    public static boolean isUDPPortAvailable(int port) {
+        try (DatagramSocket socket = new DatagramSocket(port)) {
+            return true;
+        } catch (IOException e) {
+            log.debug("Failed to open UDP port {}", port, e);
+            return false;
+        }
+    }
+}

msa/black-box-tests/src/test/java/org/thingsboard/server/msa/connectivity/lwm2m/AbstractLwm2mClientTest.java

@@ -57,12 +57,12 @@ import org.thingsboard.server.common.data.page.PageLink;
 import org.thingsboard.server.common.data.security.DeviceCredentials;
 import org.thingsboard.server.common.data.security.DeviceCredentialsType;
 import org.thingsboard.server.msa.AbstractContainerTest;
+import org.thingsboard.server.msa.PortFinder;
 import org.thingsboard.server.msa.WsClient;
 import org.thingsboard.server.msa.connectivity.lwm2m.client.LwM2MTestClient;
 import org.thingsboard.server.msa.connectivity.lwm2m.client.Lwm2mTestHelper.LwM2MClientState;
 import org.thingsboard.server.msa.mapper.WsTelemetryResponse;
 
-import java.net.ServerSocket;
 import java.nio.charset.StandardCharsets;
 import java.time.Instant;
 import java.util.ArrayList;
@@ -229,10 +229,8 @@ public class AbstractLwm2mClientTest extends AbstractContainerTest {
                                            String endpoint, ScheduledExecutorService executor) throws Exception {
         this.executor = executor;
         LwM2MTestClient lwM2MTestClient = new LwM2MTestClient(executor, endpoint);
-        try (ServerSocket socket = new ServerSocket(0)) {
-            int clientPort = socket.getLocalPort();
-            lwM2MTestClient.init(security, clientPort);
-        }
+        int clientPort = PortFinder.findAvailableUdpPort();
+        lwM2MTestClient.init(security, clientPort);
         return lwM2MTestClient;
     }
 

msa/black-box-tests/src/test/java/org/thingsboard/server/msa/connectivity/lwm2m/client/LwM2MTestClient.java

@@ -65,6 +65,7 @@ import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.awaitility.Awaitility.await;
 import static org.eclipse.californium.scandium.config.DtlsConfig.DTLS_CONNECTION_ID_LENGTH;
 import static org.eclipse.californium.scandium.config.DtlsConfig.DTLS_RECOMMENDED_CIPHER_SUITES_ONLY;
 import static org.eclipse.leshan.core.LwM2mId.ACCESS_CONTROL;
@@ -72,6 +73,7 @@ import static org.eclipse.leshan.core.LwM2mId.DEVICE;
 import static org.eclipse.leshan.core.LwM2mId.FIRMWARE;
 import static org.eclipse.leshan.core.LwM2mId.SECURITY;
 import static org.eclipse.leshan.core.LwM2mId.SERVER;
+import static org.thingsboard.server.msa.PortFinder.isUDPPortAvailable;
 import static org.thingsboard.server.msa.connectivity.lwm2m.client.Lwm2mTestHelper.BINARY_APP_DATA_CONTAINER;
 import static org.thingsboard.server.msa.connectivity.lwm2m.client.Lwm2mTestHelper.LwM2MClientState.ON_BOOTSTRAP_FAILURE;
 import static org.thingsboard.server.msa.connectivity.lwm2m.client.Lwm2mTestHelper.LwM2MClientState.ON_BOOTSTRAP_STARTED;
@@ -95,7 +97,6 @@ import static org.thingsboard.server.msa.connectivity.lwm2m.client.Lwm2mTestHelp
 import static org.thingsboard.server.msa.connectivity.lwm2m.client.Lwm2mTestHelper.serverId;
 import static org.thingsboard.server.msa.connectivity.lwm2m.client.Lwm2mTestHelper.shortServerId;
 
-
 @Slf4j
 @Data
 public class LwM2MTestClient {
@@ -115,8 +116,11 @@ public class LwM2MTestClient {
     private int countUpdateRegistrationSuccess;
     private int countReadObserveAfterUpdateRegistrationSuccess;
 
+    private int clientPort;
+
     public void init(Security security, int clientPort) throws InvalidDDFFileException, IOException {
         assertThat(leshanClient).as("client already initialized").isNull();
+        this.clientPort = clientPort;
 
         List<ObjectModel> models = new ArrayList<>();
         for (String resourceName : resources) {
@@ -342,12 +346,27 @@ public class LwM2MTestClient {
             }
         });
 
+    }
+
+    public void start() {
         leshanClient.start();
+        if (clientPort > 0) {
+            log.error("Await UDP clientPort {} to be available before leshanClient.start()", clientPort);
+            await("Await UDP clientPort " + clientPort + " to be available before leshanClient.start()")
+                    .atMost(30, TimeUnit.SECONDS)
+                    .until(() -> isUDPPortAvailable(clientPort));
+        }
     }
 
     public void destroy() {
         if (leshanClient != null) {
             leshanClient.destroy(true);
+            if (clientPort > 0) {
+                log.error("Await UDP clientPort {} to disconnect after leshanClient.stop(deregister)", clientPort);
+                await("Await client UDP port " + clientPort + " to disconnect after leshanClient.stop(deregister)")
+                        .atMost(30, TimeUnit.SECONDS)
+                        .until(() -> isUDPPortAvailable(clientPort));
+            }
         }
         if (lwM2MDevice != null) {
             lwM2MDevice.destroy();