XML-RPC call [requestTopic] didn't return an array

rgleichman commented 10 years ago

I am publishing to the /r_gripper_controller/gripper_action/goal from roshask. The /r_gripper_controller/gripper_action_node subscribes to that topic. The roshask node seems to be publishing the topic correctly (rostopic info /r_gripper_controller/gripper_action/goal prints out the correct messages), but the gripper_action_node does not produce the correct output (/r_gripper_controller/command messages). Using rxconsole I found that when the roshask node starts, the gripper_action_node emits the debug message

XML-RPC call [requestTopic] didn't return an array

after what I think is a normal message Began asynchronous xmlrpc connection to [rll3:47128] (rll3 is the machine name). The gripper_action_node is started with roslaunch pr2_gazebo pr2_empty_world.launch. I am running ROS Fuerte on Ubuntu 12.04. Here the source that logs the debug message (line 202). The equivalent Python program actuates the simulated gripper and does not produce the XML-RPC call ... debug message.

Full rxconsole paste, and roshask program below: rxconsole paste:

header: 
  seq: 394386
  stamp: 3827.744000000
  frame_id: 
level: 1
name: /r_gripper_controller/gripper_action_node
msg: Began asynchronous xmlrpc connection to [rll3:47128]
file: /tmp/buildd/ros-fuerte-ros-comm-1.8.16-1precise-20130502-1635/clients/cpp/roscpp/src/libros/subscription.cpp
function: Subscription::negotiateConnection
line: 419
topics[]
  topics[0]: /rosout
  topics[1]: /r_gripper_controller/gripper_action/result
  topics[2]: /r_gripper_controller/gripper_action/feedback
  topics[3]: /r_gripper_controller/gripper_action/status
  topics[4]: /r_gripper_controller/command

header: 
  seq: 394440
  stamp: 3828.418000000
  frame_id: 
level: 1
name: /r_gripper_controller/gripper_action_node
msg: XML-RPC call [requestTopic] didn't return an array
file: /tmp/buildd/ros-fuerte-ros-comm-1.8.16-1precise-20130502-1635/clients/cpp/roscpp/src/libros/xmlrpc_manager.cpp
function: XMLRPCManager::validateXmlrpcResponse
line: 203
topics[]
  topics[0]: /rosout
  topics[1]: /r_gripper_controller/gripper_action/result
  topics[2]: /r_gripper_controller/gripper_action/feedback
  topics[3]: /r_gripper_controller/gripper_action/status
  topics[4]: /r_gripper_controller/command

My roshask program

module GripperTalker (main) where

import Ros.Node (Topic)
import Ros.Node (topicRate)
import Ros.Node (runNode)
import Ros.Node (advertise)
import Ros.Topic (repeatM)
import Ros.Pr2_controllers_msgs.Pr2GripperCommandGoal
import Ros.Pr2_controllers_msgs.Pr2GripperCommandActionGoal
import Ros.Pr2_controllers_msgs.Pr2GripperCommand
import qualified Ros.Std_msgs.Header as H
import qualified Ros.Actionlib_msgs.GoalID as GID

open :: Double
open = 0.09

closed :: Double
closed = 0.0

moveGripper :: Topic IO Pr2GripperCommandActionGoal
moveGripper = repeatM msg
  where msg = return $ Pr2GripperCommandActionGoal{
          header= H.Header {H.seq= 0,
                            H.stamp = (0,0),
                            H.frame_id= ""},
          goal_id= GID.GoalID {
            GID.stamp = (0,0),
            GID.id = ""
                          },
          goal=Pr2GripperCommandGoal{
             command = Pr2GripperCommand{
                position = 0.09, max_effort = (-1)
                                        }
             }
          }

main :: IO ()
main = runNode "GripperTakler" $ advertise topicName (topicRate 1 moveGripper)
  where topicName = "/r_gripper_controller/gripper_action/goal"