XML-RPC Communication with Universal Robots

Introduction

XML-RPC (XML Remote Procedure Call) enables communication between the UR controller and external programs by invoking remote methods over HTTP, with XML as the data format. This tutorial demonstrates how to use XML-RPC to move a Universal Robot to a target pose provided by a remote program. Examples are provided for both Python and C++.

Attached Files

xmlrpc.urp

xmlrpc.zip

Setting Up the Robot Program

1. Create a URP Program: Download and configure xmlrpc_example.urp in the PolyScope environment. In the BeforeStart sequence, establish a connection to the remote server named “camera”. During the robot program, invoke the get_next_pose function to retrieve the next target pose and move the robot using MoveJ.

Python Example

1. Install Dependencies:

   • Python 2.7 or 3.x

   • SimpleXMLRPCServer for Python 2, or xmlrpc.server for Python 3.

2. Create Server Script (xmlrpc_camera.py):

   import sys
   import urlib
   
   is_py2 = sys.version[0] == '2'
   if is_py2:
       from SimpleXMLRPCServer import SimpleXMLRPCServer
   else:
       from xmlrpc.server import SimpleXMLRPCServer
   
   def get_next_pose(p):
       assert type(p) is dict
       pose = urlib.poseToList(p)
       print("Received pose: " + str(pose))
       pose = [-0.18, -0.61, 0.23, 0, 3.12, 0.04]
       return urlib.listToPose(pose)
   
   server = SimpleXMLRPCServer(("", 50000), allow_none=True)
   server.RequestHandlerClass.protocol_version = "HTTP/1.1"
   print("Listening on port 50000...")
   server.register_function(get_next_pose, "get_next_pose")
   server.serve_forever()
   

3. Run the Server:

   python xmlrpc_camera.py
   

C++ Example

1. Install Dependencies:

   sudo apt-get update
   sudo apt-get install libxmlrpc-c++8 g++
   

2. Create Server Script:

   • Download xmlrpc_cpp.zip and compile using:

   tar xf xmlrpc_cpp.zip
   make
   ./xmlrpc_camera
   

Running the Examples

1. Configure UR Program: Transfer xmlrpc_example.urp to the robot and update the IP address in the script to match your server’s IP.

2. Execute the UR Program: Run the PolyScope program. The robot should move to the pose returned by the remote server.

Conclusion

XML-RPC facilitates flexible and straightforward communication between a UR robot and external systems, allowing remote procedures to control the robot. The provided Python and C++ examples illustrate how to set up and run an XML-RPC server to control the robot’s movements based on remote commands.