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 e9b67ac9..4f3492d8 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
@@ -132,7 +132,8 @@ public class RtkClusterService implements ApplicationRunner {
                     if (sid != null) {
                         RtkrcvSession upd = new RtkrcvSession();
                         upd.setSessionId(sid);
-                        upd.setPid((int) p.pid());
+                        Integer pid = tryGetPidCompat(p);
+                        if (pid != null) upd.setPid(pid);
                         upd.setStartTime(LocalDateTime.now());
                         upd.setUpdatedAt(LocalDateTime.now());
                         sessionMapper.updateById(upd);
@@ -212,6 +213,18 @@ public class RtkClusterService implements ApplicationRunner {
         }
     }
 
+    // Java 8-only attempt to get Process pid; returns null if unavailable
+    private Integer tryGetPidCompat(Process p) {
+        try {
+            // Access private 'pid' field on UNIXProcess (Java 8)
+            java.lang.reflect.Field f = p.getClass().getDeclaredField("pid");
+            f.setAccessible(true);
+            Object v = f.get(p);
+            if (v instanceof Integer) return (Integer) v;
+        } catch (Exception ignore) {}
+        return null;
+    }
+
     static class DeviceEndpoint {
         private final String deviceId;
         private final int port;