# External\_control gets blocked by own URScript

**URL:** <https://forum.universal-robots.com/t/external-control-gets-blocked-by-own-urscript/32733>\
**Category:** ROS\
**Created:** [February 14, 2024, 3:01pm UTC](https://forum.universal-robots.com/t/external-control-gets-blocked-by-own-urscript/32733 "2024-02-14T15:01:57Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![NotARobot](https://avatars.discourse-cdn.com/v4/letter/n/f19dbf/32.png) [@NotARobot](https://forum.universal-robots.com/u/NotARobot)\
**Post date:** [February 14, 2024, 3:01pm UTC](https://forum.universal-robots.com/t/external-control-gets-blocked-by-own-urscript/32733/1 "2024-02-14T15:01:57Z")

</div>

Greetings. I want to control a UR with ROS2 Humble using the `external_control` URCap. This works well, including MoveIt and Pilz Industrial Motion planner. There is also a gripper mounted on the UR, which is a OnRobot RG6 V1.0 gripper. I’ve got the URCap for the gripper which also works fine from the control panel.  
In order to get control over gripper from ROS2 I’ve created a little URCap including a URScript which demands a XML-RPC connection to one of my ROS nodes. This is also working as intended, I can open and close the gripper with all parameters provided by OnRobots URCap.

If I try to use `external_control` to control the robot via ROS and my URCap is running, then I am not able to control the robot anymore. My URCap consist only of a single of each `InstallationNodeContribution`, `InstallationNodeService` and `InstallationNodeView`. Like in `external_control` these are only used to load a custom URScript snipped into the robot program.

The URScript snipped:

```auto
# BEGIN

# Constants
xmlrpc_rg6_ip = {{IP_ADDRESS}}
xmlrpc_rg6_port = {{PORT_NO}}
xmlrpc_rg6_keepalive = True

textmsg("RG6 Gripper Control: Starting XML-RPC Server for RG6 Gripper control")
xmlrpc_rg6_conn = rpc_factory("xmlrpc", "http://" + xmlrpc_rg6_ip + ":" + xmlrpc_rg6_port + "/RPC2")

thread gripperThread():
    textmsg("RG6 Gripper Control: Start thread")
    while True:
        global xmlrpc_rg6_keepalive = xmlrpc_rg6_conn.getKeepAlive()
        
        if xmlrpc_rg6_keepalive == False:
            break
        end
    
        xmlrpc_rg6_conn.setWidth(measure_width)

        local xmlrpc_rg6_width = xmlrpc_rg6_conn.getWidth()
        local xmlrpc_rg6_force = xmlrpc_rg6_conn.getForce()
        local xmlrpc_rg6_dcompensation = xmlrpc_rg6_conn.getDepthCompensation()
        local xmlrpc_rg6_payload = xmlrpc_rg6_conn.getPayload()

        if xmlrpc_rg6_payload >= 0.0:
            local xmlrpc_rg6_spayload = False
        else:
            local xmlrpc_rg6_spayload = True
        end
        
        # This command is only available if OnRobot URCap (RG - OnRobot v1.10.1) is installed
        RG6(target_width = xmlrpc_rg6_width, target_force = xmlrpc_rg6_force, payload = xmlrpc_rg6_payload, set_payload = xmlrpc_rg6_spayload, depth_compensation = xmlrpc_rg6_dcompensation)
    end
    textmsg("RG6 Gripper Control: Stop thread")
    return False
end

if xmlrpc_rg6_keepalive:
    global xmlrpc_rg6_thread = run gripperThread()
end

join xmlrpc_rg6_thread
textmsg("RG6 Gripper Control: XML-RPC Server for RG6 Gripper control stopped")

# END

```

In RViz I can see the robot, its current pose, plan and execute the planned path. The `ros2_control` controller returns execution succeeded after ordering path execution.

What is the problem? Is my snipped blocking the external\_control execution?

---

<div class="post-metadata">

**Author:** ![NotARobot](https://avatars.discourse-cdn.com/v4/letter/n/f19dbf/32.png) [@NotARobot](https://forum.universal-robots.com/u/NotARobot)\
**Post date:** [February 15, 2024, 10:31am UTC](https://forum.universal-robots.com/t/external-control-gets-blocked-by-own-urscript/32733/2 "2024-02-15T10:31:10Z")

</div>

Problem solved, to end the gripper control, the thread shouldn’t be joined but killed.

Removed line: `join xmlrpc_rg6_thread`  
Modified lines:

```auto
if xmlrpc_rg6_keepalive:
    global xmlrpc_rg6_thread = run gripperThread()
end

```

to

```auto
if xmlrpc_rg6_keepalive:
    global xmlrpc_rg6_thread = run gripperThread()
else:
    kill xmlrpc_rg6_thread
end

```

---

<div class="post-metadata">

**Author:** ![vi.hi](https://avatars.discourse-cdn.com/v4/letter/v/8797f3/32.png) [@vi.hi](https://forum.universal-robots.com/u/vi.hi)\
**Post date:** [May 15, 2024, 10:01am UTC](https://forum.universal-robots.com/t/external-control-gets-blocked-by-own-urscript/32733/3 "2024-05-15T10:01:58Z")

</div>

Could you provide the URCap?

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<div class="post-metadata">

**Author:** ![cny](https://avatars.discourse-cdn.com/v4/letter/c/cab0a1/32.png) [@cny](https://forum.universal-robots.com/u/cny)\
**Post date:** [July 14, 2025, 1:36pm UTC](https://forum.universal-robots.com/t/external-control-gets-blocked-by-own-urscript/32733/4 "2025-07-14T13:36:46Z")

</div>

Hello, please provie the urcap and explain more of your setup . Questions:  
1)is your tool io controled byonrobot or user?  
2)when running what is your launch command  
3)how does your program look like

thank you