Refactor tool communication into standalone socat initialization script (UniversalRobots#470)

- The `tool_communication.py` logic has been moved to
`ur_client_library`.
- The script is no longer implemented as a ROS node.
- The script can be executed independently and focuses solely on
initializing the `socat` bridge.
- Improved error handling has been added directly to the script.

Author: srvald

CMakeLists.txt

@@ -154,7 +154,10 @@ if(CATKIN_PACKAGE_BIN_DESTINATION)
     DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}
   )
 else()
-  install(PROGRAMS scripts/start_ursim.sh
+  install(
+    PROGRAMS 
+      scripts/start_ursim.sh
+      scripts/tool_communication.py
     DESTINATION lib/${PROJECT_NAME}
   )
 endif()
@@ -186,4 +189,4 @@ file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/share/${PROJECT_NAME}/hook/ros_package_pa
 install(FILES ${CMAKE_CURRENT_BINARY_DIR}/share/${PROJECT_NAME}/hook/ros_package_path.dsv DESTINATION share/${PROJECT_NAME}/hook)
 #### End iport ####
 
-install(DIRECTORY resources DESTINATION share/${PROJECT_NAME})
+install(DIRECTORY resources DESTINATION share/${PROJECT_NAME})

scripts/tool_communication.py

@@ -0,0 +1,162 @@
+#!/usr/bin/env python3
+# -- BEGIN LICENSE BLOCK ----------------------------------------------
+# Copyright 2026 Universal Robots A/S
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+#    * Redistributions of source code must retain the above copyright
+#      notice, this list of conditions and the following disclaimer.
+#
+#    * Redistributions in binary form must reproduce the above copyright
+#      notice, this list of conditions and the following disclaimer in the
+#      documentation and/or other materials provided with the distribution.
+#
+#    * Neither the name of the {copyright_holder} nor the names of its
+#      contributors may be used to endorse or promote products derived from
+#      this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+# -- END LICENSE BLOCK ------------------------------------------------
+
+
+"""Small helper script to start the tool communication interface."""
+
+import subprocess
+import logging
+import argparse
+import socket
+import os
+
+
+# Custom formatter to show both default values and description formatting in the help message
+class Formatter(argparse.ArgumentDefaultsHelpFormatter, argparse.RawDescriptionHelpFormatter):
+    pass
+
+
+def get_args():
+    # Arguments to configure socat
+    arg = argparse.ArgumentParser(
+        description=(
+            "Starts socat to create a PTY symlink for the UR tool communication interface."
+        ),
+        epilog="""
+IMPORTANT:
+
+This script requires the ToolComm Forwarder URCap to be running on the robot.
+Make sure it is installed and started before launching this script.
+
+More information can be found in the following ToolComm Forwarder URCap repositories:
+  - ToolComm Forwarder URCap (Polyscope X):
+    https://github.com/UniversalRobots/Universal_Robots_ToolComm_Forwarder_URCapX
+  - ToolComm Forwarder URCap (Polyscope 5)
+    https://github.com/UniversalRobots/Universal_Robots_ToolComm_Forwarder_URCap
+
+For background information on how tool communication works on UR robots, see:
+https://docs.universal-robots.com/Universal_Robots_ROS2_Documentation/doc/ur_robot_driver/ur_robot_driver/doc/setup_tool_communication.html
+        """,
+        formatter_class=Formatter
+    )
+
+    arg.add_argument("robot_ip", help="IP address of the robot to connect to.")
+    arg.add_argument("--tcp-port", type=int, default=54321, help="TCP Port. Likely, this should not be changed")
+    arg.add_argument("--device-name", default="/tmp/ttyUR", help="PTY symlink device name.")
+    return arg.parse_args()
+
+
+def check_tcp(ip, port, timeout=5.0):
+    try:
+        with socket.create_connection((ip, port), timeout=timeout):
+            return True
+    except OSError:
+        return False
+
+
+def main(args):
+    RED = "\033[31m"
+    RESET = "\033[0m"
+
+    logging.basicConfig(level=logging.INFO, format="[%(levelname)s] %(message)s")
+
+    # Get parameters from arguments
+    robot_ip = args.robot_ip
+    logging.info("Robot IP: " + robot_ip)
+    tcp_port = args.tcp_port
+    logging.info("TCP Port: " + str(tcp_port))
+    local_device = args.device_name
+
+    # Check IP and port reachability
+    if not check_tcp(robot_ip, tcp_port):
+        logging.error(
+            f"{RED}Cannot reach {robot_ip}:{tcp_port}.\n"
+            "Check that the IP address and port are correct.\n"
+            "If so, ensure that the robot is powered on, reachable on the network, "
+            f"and that the ToolCommForwarder URCap is running.{RESET}"
+        )
+        logging.info("Exiting tool communication script.")
+        return
+
+    # Check if the device_name is a directory
+    if os.path.isdir(local_device):
+
+        logging.error(
+            f"{RED}'{local_device}' exists and is a directory.\n"
+            "Socat needs a file path to create a PTY symlink, but it cannot replace a directory.\n"
+            "Fix:\n"
+            "  - Remove the directory.\n"
+            f"  - Use a different device name, e.g. '--device-name /tmp/ttyUR0'. {RESET}"
+        )
+        logging.info("Exiting tool communication script.")
+        return
+
+    # Configure socat command
+    socat_config = [
+        "pty",
+        f"link={local_device}",
+        "raw",
+        "ignoreeof",
+        "waitslave",
+    ]
+
+    socat_command = [
+        "socat",
+        ",".join(socat_config),
+        f"tcp:{robot_ip}:{tcp_port}",
+    ]
+
+    logging.info(f"Configuring PTY symlink at '{local_device}'")
+
+    # Start socat
+    try:
+        logging.info("Starting socat with following command:\n" + " ".join(socat_command))
+        subprocess.call(socat_command)
+        logging.info("Socat terminated")
+
+    # Error case when socat is not installed
+    except FileNotFoundError:
+        logging.error(f"{RED}Socat not found in PATH. Install it (e.g. apt-get install socat). {RESET}")
+        logging.info("Exiting tool communication script.")
+        return
+
+    # Other errors
+    except Exception as e:
+        logging.error(f"{RED}Unexpected error launching socat: {e} {RESET}")
+        logging.info("Exiting tool communication script.")
+        return
+
+    return
+
+
+if __name__ == "__main__":
+    args = get_args()
+    main(args)