1 files changed, 9 insertions, 5 deletions
diff --git a/src/org/traccar/database/CommandsManager.java b/src/org/traccar/database/CommandsManager.java
index f9feb927d..cae4ac6f7 100644
--- a/src/org/traccar/database/CommandsManager.java
+++ b/src/org/traccar/database/CommandsManager.java
@@ -22,7 +22,9 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 import java.util.Map;
+import java.util.Queue;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentLinkedQueue;
 
 import org.traccar.BaseProtocol;
 import org.traccar.Context;
@@ -33,7 +35,7 @@ import org.traccar.model.Position;
 
 public class CommandsManager  extends ExtendedObjectManager<Command> {
 
-    private final Map<Long, List<Command>> deviceQueues = new ConcurrentHashMap<>();
+    private final Map<Long, Queue<Command>> deviceQueues = new ConcurrentHashMap<>();
 
     public CommandsManager(DataManager dataManager) {
         super(dataManager, Command.class);
@@ -125,18 +127,20 @@ public class CommandsManager  extends ExtendedObjectManager<Command> {
         return result;
     }
 
-    private List<Command> getDeviceQueue(long deviceId) {
+    private Queue<Command> getDeviceQueue(long deviceId) {
         if (!deviceQueues.containsKey(deviceId)) {
-            deviceQueues.put(deviceId, new ArrayList<Command>());
+            deviceQueues.put(deviceId, new ConcurrentLinkedQueue<Command>());
         }
         return deviceQueues.get(deviceId);
     }
 
     public void sendQueuedCommands(ActiveDevice activeDevice) {
-        List<Command> deviceQueue = deviceQueues.get(activeDevice.getDeviceId());
+        Queue<Command> deviceQueue = deviceQueues.get(activeDevice.getDeviceId());
         if (deviceQueue != null) {
-            for (Command command : deviceQueue) {
+            Command command = deviceQueue.poll();
+            while (command != null) {
                 activeDevice.sendCommand(command);
+                command = deviceQueue.poll();
             }
         }
     }