#URScript_socket_example.md

#URScript_socket_example.md

Overview

• This file demonstrates how to use transmission control protocol (TCP) sockets in Universal Robot's (UR) proprietary programming language URScript.
• This example uses the official UR simulator running a UR3e on Virtual Box; an actual cobot can be used instead.
• Critical points:
  • A computer is used to instantiate a server using Python that is listening on its internet protocol address at port 8080.
  • A URScript file is loaded into the cobot's programming interface; this script connects with the computer then sends a request message with payload "Hello World".

Requirements

1. Install Python3
2. Install / setup UR simulator; ensure the network setting in step5 are correct.

Demonstration

1. Create a Python file and copy / paste this generic server script; no modifications should be necessary.

   # server.py
   # This program starts a server, receives request message then displays data.
   import socket
   import sys
   
   # Used to safely terminate on keyboard interrupt.
   def handle_keyboard_interrupt(client_socket, server_socket):
       print("Received KeyboardInterrupt, shutting down the server...")
       client_socket.close()
       server_socket.close()
       sys.exit(0)
   
   # Used to receive the data in chunks and print it out.
   def receive_data(client_socket, server_socket):
       try:
           while True:
               data = client_socket.recv(1024)
               if not data:
                   break
               print("Received data: {}".format(data.decode()))
       except KeyboardInterrupt:
           handle_keyboard_interrupt(client_socket, server_socket)
   
   # Opens TCP socket, listens, binds then receives and displays data.
   # Terminates safely when the client closes connection or keyboard interrupt.
   def main():
       HOST_IP_ADDRESS = socket.gethostbyname(socket.gethostname())
       PORT = 8080 
   
       # create a TCP/IP socket
       server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
   
       try:
           server_socket.bind((HOST_IP_ADDRESS, PORT))
       except socket.error as e:
           print("Error binding the socket: {}".format(e))
           sys.exit(1)
   
       try:
           server_socket.listen()
       except socket.error as e:
           print("Error listening on the socket: {}".format(e))
           sys.exit(1)
   
       print("Listening on {}:{}".format(HOST_IP_ADDRESS, PORT))
   
       print("Waiting for a connection...")
       try:
           client_socket, client_address = server_socket.accept()
       except socket.error as e:
           print("Error accepting a connection: {}".format(e))
           sys.exit(1)
   
       print("Accepted connection from {}".format(client_address))
   
       receive_data(client_socket, server_socket)
   
       # close the connection
       client_socket.close()
       server_socket.close()
   
   if __name__ == '__main__':
       main()

2. Start the simulator, turn the robot on then add the following URScript with your computer's IP address into its program using these actions:

   URScript

   NOTE: If you start the above Python script, your IP address will be displayed in console.

   socket_open("<ADD_YOUR_COMPUTERS_IP_ADDRESS>", 8080)
   socket_send_string("Hello World")
   

   Actions

   

3. Start the server, activate the cobot's simulation mode then execute the script.

   

Additional Script Examples

Example1

URScript

current = get_actual_joint_positions()
socket_open("<ADD_YOUR_COMPUTERS_IP_ADDRESS>", 8080)
socket_send_string(current)

Output

Listening on IP address10.0.0.25, port 8080
Waiting for a connection...
Accepted connection from ('10.0.0.133', 48407)
Received data: [-1.6007,-1.7271,-2.203,-0.808,1.5951,-0.031]

Example2

URScript

current = get_controller_temp()
socket_open("<ADD_YOUR_COMPUTERS_IP_ADDRESS>", 8080)
socket_send_string(current)

Output

Listening on IP address10.0.0.25, port 8080
Waiting for a connection...
Accepted connection from ('10.0.0.133', 48408)
Received data: 24

Final Remarks

• The current problem with the OpenTAP UR plugin prototype is that it cannot receive meaningful data from the cobot because the response messages from the cobot are serialized. I cannot identify any resource used for a client to deserialize the message. This is an issue because we won't be able to curate data from the cobot that might be useful test specs.
• This demonstration hints that there is an internal URScript module in between the controller and URScript sockets that is decoding the message.
• The encoding might be related to UR's real time data exchange protocol. I read on the UR forum that someone was able to decode messages using the ROS2 driver.