diff --git a/sec-beidou-rtcm/src/main/java/com/imdroid/sideslope/rtkcluster/RtkClusterService.java b/sec-beidou-rtcm/src/main/java/com/imdroid/sideslope/rtkcluster/RtkClusterService.java
index 263f75ae..31545cf2 100644
--- a/sec-beidou-rtcm/src/main/java/com/imdroid/sideslope/rtkcluster/RtkClusterService.java
+++ b/sec-beidou-rtcm/src/main/java/com/imdroid/sideslope/rtkcluster/RtkClusterService.java
@@ -103,7 +103,7 @@ public class RtkClusterService implements ApplicationRunner {
     private void bootstrapDevice(RtkrcvProfile profile, int workPort) throws IOException {
         String deviceId = profile.getDeviceId();
         // 1) Start endpoint server (if not exists)
-        endpoints.computeIfAbsent(deviceId, k -> new DeviceEndpoint(deviceId, workPort,
+        endpoints.computeIfAbsent(deviceId, k -> new DeviceEndpoint(this, deviceId, workPort,
                 () -> onOutEstablished(deviceId)));
         DeviceEndpoint ep = endpoints.get(deviceId);
         ep.ensureStarted();
@@ -251,6 +251,7 @@ public class RtkClusterService implements ApplicationRunner {
     }
 
     static class DeviceEndpoint {
+        private final RtkClusterService parent;
         private final String deviceId;
         private final int port;
         private final ExecutorService exec;
@@ -263,7 +264,8 @@ public class RtkClusterService implements ApplicationRunner {
         private final java.util.concurrent.LinkedBlockingDeque<byte[]> rtcmQueue = new java.util.concurrent.LinkedBlockingDeque<>(1024);
         private final Runnable onOutEstablished;
 
-        DeviceEndpoint(String deviceId, int port, Runnable onOutEstablished) {
+        DeviceEndpoint(RtkClusterService parent, String deviceId, int port, Runnable onOutEstablished) {
+            this.parent = parent;
             this.deviceId = deviceId;
             this.port = port;
             this.onOutEstablished = onOutEstablished;
@@ -357,7 +359,7 @@ public class RtkClusterService implements ApplicationRunner {
                         }
                         String preview = new String(buf, 0, read, StandardCharsets.US_ASCII).replaceAll("\n", "\\n");
                         LOGGER.info("[OUT:{}] {}", port, preview);
-                        notifyOut(deviceId, preview);
+                        if (parent != null) parent.notifyOut(deviceId, preview);
                     }
                 } catch (IOException e) {
                     LOGGER.debug("Connection reader closed on {}: {}", port, e.getMessage());
@@ -469,7 +471,7 @@ public class RtkClusterService implements ApplicationRunner {
         if (ep == null) {
             // derive a stable port for group endpoints to avoid collisions
             int port = basePort + 10000 + (int) (Math.floorMod(groupId, 50000));
-            endpoints.computeIfAbsent(key, k -> new DeviceEndpoint(key, port, null));
+            endpoints.computeIfAbsent(key, k -> new DeviceEndpoint(this, key, port, null));
             ep = endpoints.get(key);
             ep.ensureStarted();
             LOGGER.info("Group endpoint ready for {} on 127.0.0.1:{}", key, port);