diff --git a/script/RobotTCP.py b/script/RobotTCP.py
index d9d2ae0..5f9381a 100644
--- a/script/RobotTCP.py
+++ b/script/RobotTCP.py
@@ -1,4 +1,4 @@
-
+import threading
 
 class RobotTCP(TcpDevice, Stoppable):    
     def __init__(self, name, server, timeout = 500, retries = 1):
@@ -17,26 +17,31 @@ class RobotTCP(TcpDevice, Stoppable):
          self.empty = None
          self.working_mode = None
          self.status = None
+         self.lock = threading.Lock()
+    
+    def _sendReceive(self, msg_id, msg = ""):  
+        self.lock.acquire()
+        try:
+            tx = self.header if (self.header != None) else  ""
+            tx = tx + msg_id + " " + msg        
+            if (len(tx)>127):
+                raise Exception("Exceeded maximum message size")
+            self.getLogger().finer("TX = '" +  str(tx)+ "'")
+            if (self.trailer != None): tx = tx + self.trailer
+            rx = self.sendReceive(tx, None, self.trailer , 0,  self.timeout, self.retries)
+            rx=rx[:-1] #Remove 0A
+            self.getLogger().finer("RX = '" + str(rx) + "'")
+            if rx[:3] != msg_id:           
+                print rx 
+                raise Exception("Received invalid message id: " + str(rx[:3]) + " - expecting:" + msg_id )
+            if len(rx)<4:
+                raise Exception("Invalid message size: " + str(len(rx)) )        
+            if rx[3] == "*":
+                raise Exception(rx[4:])
+            return rx[4:]
+        finally:
+            self.lock.release()
     
-    def _sendReceive(self, msg_id, msg = ""):        
-        tx = self.header if (self.header != None) else  ""
-        tx = tx + msg_id + " " + msg        
-        if (len(tx)>127):
-            raise Exception("Exceeded maximum message size")
-        self.getLogger().finer("TX = '" +  str(tx)+ "'")
-        if (self.trailer != None): tx = tx + self.trailer
-        rx = self.sendReceive(tx, None, self.trailer , 0,  self.timeout, self.retries)
-        rx=rx[:-1] #Remove 0A
-        self.getLogger().finer("RX = '" + str(rx) + "'")
-        if rx[:3] != msg_id:           
-            print rx 
-            raise Exception("Received invalid message id: " + str(rx[:3]) + " - expecting:" + msg_id )
-        if len(rx)<4:
-            raise Exception("Invalid message size: " + str(len(rx)) )        
-        if rx[3] == "*":
-            raise Exception(rx[4:])
-        return rx[4:]
-
     def call(self, msg):                
         id = "%03d" % self.msg_id
         self.msg_id = (self.msg_id+1)%1000