ROS Basics in 5 days (C++) | (3.3) Service client module |

Course Support ROS Basics In 5 Days (C++)
1

Hi, I am going through the ROS Services module in the above course. I get this error on launch:

ERROR: cannot launch node of type [service_client_pkg/service_client_pkg_node]: Cannot locate node of type [service_client_pkg_node] in package [service_client_pkg]. Make sure file exists in package path and permission is set to executable (chmod +x)

The file exists and has the correct permissions. I don’t really know why I’m getting this error message, and what to do about it. Any help would be appreciated.

Launch file:

<launch>

<include file="$(find trajectory_by_name)/launch/start_service.launch"/>
    <node pkg="service_client_pkg"
          type="service_client_pkg_node"
          name="service_client"
          output="screen">

    </node>
</launch>

Cpp file: service_client_pkg_node.cpp

#include "ros/ros.h"
#include "trajectory_by_name_srv/ls.h"
// Import the service message used by the service /trajectory_by_name

int main(int argc, char **argv) {
  ros::init(
      argc, argv,
      "service_client"); // Initialise a ROS node with the name service_client
  ros::NodeHandle nh;

  // Create the connection to the service /trajectory_by_name
  ros::ServiceClient traj_by_name_service =
      nh.serviceClient<trajectory_by_name_srv::TrajByName>(
          "/trajectory_by_name");
  trajectory_by_name_srv::TrajByName srv; // Create an object of type TrajByName
  srv.request.traj_name =
      "release_food"; // Fill the variable traj_name with the desired value

  if (traj_by_name_service.call(srv)) // Send through the connection the name of
                                      // the trajectory to execute
  {
    ROS_INFO("%s",
             srv.response.status_message
                 .c_str()); // Print the result given by the service called
  } else {
    ROS_ERROR("Failed to call service /trajectory_by_name");
    return 1;
  }

  return 0;
}

CMakeLists.txt file:

cmake_minimum_required(VERSION 3.0.2)

project(service_client_pkg)

## Compile as C++11, supported in ROS Kinetic and newer

# add_compile_options(-std=c++11)

## Find catkin macros and libraries

## if COMPONENTS list like find_package(catkin REQUIRED COMPONENTS xyz)

## is used, also find other catkin packages

find_package(catkin REQUIRED COMPONENTS

  roscpp

  trajectory_by_name_srv

  message_generation

)

## System dependencies are found with CMake's conventions

# find_package(Boost REQUIRED COMPONENTS system)

## Uncomment this if the package has a setup.py. This macro ensures

## modules and global scripts declared therein get installed

## See http://ros.org/doc/api/catkin/html/user_guide/setup_dot_py.html

# catkin_python_setup()

################################################

## Declare ROS messages, services and actions ##

################################################

## To declare and build messages, services or actions from within this

## package, follow these steps:

## * Let MSG_DEP_SET be the set of packages whose message types you use in

##   your messages/services/actions (e.g. std_msgs, actionlib_msgs, ...).

## * In the file package.xml:

##   * add a build_depend tag for "message_generation"

##   * add a build_depend and a exec_depend tag for each package in MSG_DEP_SET

##   * If MSG_DEP_SET isn't empty the following dependency has been pulled in

##     but can be declared for certainty nonetheless:

##     * add a exec_depend tag for "message_runtime"

## * In this file (CMakeLists.txt):

##   * add "message_generation" and every package in MSG_DEP_SET to

##     find_package(catkin REQUIRED COMPONENTS ...)

##   * add "message_runtime" and every package in MSG_DEP_SET to

##     catkin_package(CATKIN_DEPENDS ...)

##   * uncomment the add_*_files sections below as needed

##     and list every .msg/.srv/.action file to be processed

##   * uncomment the generate_messages entry below

##   * add every package in MSG_DEP_SET to generate_messages(DEPENDENCIES ...)

## Generate messages in the 'msg' folder

# add_message_files(

#   FILES

#   Message1.msg

#   Message2.msg

# )

## Generate services in the 'srv' folder

add_service_files(

   FILES

   TrajByName

#   Service1.srv

#   Service2.srv

)

## Generate actions in the 'action' folder

# add_action_files(

#   FILES

#   Action1.action

#   Action2.action

# )

## Generate added messages and services with any dependencies listed here

generate_messages(

   DEPENDENCIES

#   std_msgs  # Or other packages containing msgs

)

################################################

## Declare ROS dynamic reconfigure parameters ##

################################################

## To declare and build dynamic reconfigure parameters within this

## package, follow these steps:

## * In the file package.xml:

##   * add a build_depend and a exec_depend tag for "dynamic_reconfigure"

## * In this file (CMakeLists.txt):

##   * add "dynamic_reconfigure" to

##     find_package(catkin REQUIRED COMPONENTS ...)

##   * uncomment the "generate_dynamic_reconfigure_options" section below

##     and list every .cfg file to be processed

## Generate dynamic reconfigure parameters in the 'cfg' folder

# generate_dynamic_reconfigure_options(

#   cfg/DynReconf1.cfg

#   cfg/DynReconf2.cfg

# )

###################################

## catkin specific configuration ##

###################################

## The catkin_package macro generates cmake config files for your package

## Declare things to be passed to dependent projects

## INCLUDE_DIRS: uncomment this if your package contains header files

## LIBRARIES: libraries you create in this project that dependent projects also need

## CATKIN_DEPENDS: catkin_packages dependent projects also need

## DEPENDS: system dependencies of this project that dependent projects also need

catkin_package(

#  INCLUDE_DIRS include

#  LIBRARIES service_client_pkg

   CATKIN_DEPENDS roscpp trajectory_by_name_srv message_runtime

#  DEPENDS system_lib

)

###########

## Build ## 

###########

## Specify additional locations of header files

## Your package locations should be listed before other locations

include_directories(

# include

  ${catkin_INCLUDE_DIRS}

)

## Declare a C++ library

# add_library(${PROJECT_NAME}

#   src/${PROJECT_NAME}/service_client_pkg.cpp

# )

## Add cmake target dependencies of the library

## as an example, code may need to be generated before libraries

## either from message generation or dynamic reconfigure

# add_dependencies(${PROJECT_NAME} ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})

## Declare a C++ executable

## With catkin_make all packages are built within a single CMake context

## The recommended prefix ensures that target names across packages don't collide

add_executable(${PROJECT_NAME}_node src/service_client_pkg_node.cpp)

## Rename C++ executable without prefix

## The above recommended prefix causes long target names, the following renames the

## target back to the shorter version for ease of user use

## e.g. "rosrun someones_pkg node" instead of "rosrun someones_pkg someones_pkg_node"

# set_target_properties(${PROJECT_NAME}_node PROPERTIES OUTPUT_NAME node PREFIX "")

## Add cmake target dependencies of the executable

## same as for the library above

add_dependencies(${PROJECT_NAME}_node ${${PROJECT_NAME}_node_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})

## Specify libraries to link a library or executable target against

target_link_libraries(${PROJECT_NAME}_node

   ${catkin_LIBRARIES}

)

#############

## Install ##

#############

# all install targets should use catkin DESTINATION variables

# See http://ros.org/doc/api/catkin/html/adv_user_guide/variables.html

## Mark executable scripts (Python etc.) for installation

## in contrast to setup.py, you can choose the destination

# catkin_install_python(PROGRAMS

#   scripts/my_python_script

#   DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}

# )

## Mark executables for installation

## See http://docs.ros.org/melodic/api/catkin/html/howto/format1/building_executables.html

# install(TARGETS ${PROJECT_NAME}_node

#   RUNTIME DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}

# )

## Mark libraries for installation

## See http://docs.ros.org/melodic/api/catkin/html/howto/format1/building_libraries.html

# install(TARGETS ${PROJECT_NAME}

#   ARCHIVE DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}

#   LIBRARY DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}

#   RUNTIME DESTINATION ${CATKIN_GLOBAL_BIN_DESTINATION}

# )

## Mark cpp header files for installation

# install(DIRECTORY include/${PROJECT_NAME}/

#   DESTINATION ${CATKIN_PACKAGE_INCLUDE_DESTINATION}

#   FILES_MATCHING PATTERN "*.h"

#   PATTERN ".svn" EXCLUDE

# )

## Mark other files for installation (e.g. launch and bag files, etc.)

# install(FILES

#   # myfile1

#   # myfile2

#   DESTINATION ${CATKIN_PACKAGE_SHARE_DESTINATION}

# )

#############

## Testing ##

#############

## Add gtest based cpp test target and link libraries

# catkin_add_gtest(${PROJECT_NAME}-test test/test_service_client_pkg.cpp)

# if(TARGET ${PROJECT_NAME}-test)

#   target_link_libraries(${PROJECT_NAME}-test ${PROJECT_NAME})

# endif()

## Add folders to be run by python nosetests

# catkin_add_nosetests(test)
1 Like
2

Hi @RaspyWasp,

Welcome to the Community!

For C++, this is not usually a problem of execution permission (chmod +x) - it usually means that your package has not been properly built, hence the C++ executable could not be found.

Please look into these:

  • You have modified your CMakeLists.txt file as explained. Please go over it again and ensure the necessary lines have been correctly added.
  • Build the package and source:
catkin_make
source devel/setup.bash
2 Likes
3

Hi @bayodesegun,

Thank you so much for your help!

I am honestly a little lost. I have already gone over the CMakeLists.txt, package.xml, and .launch files a few times already (also have started the package over from scratch a few times as well), but I am still not entirely sure where I am messing up.

I am very new to ROS (ROS Services specifically too), so I don’t know for sure what lines I need to modify in the CMakeLists.txt. I have read the official documentation, which said that the process of generating .srv type files is similar to building .msg format files. So, I’ve modified pretty much that same information in my current CMakeLists.txt that I would when generating a custom message. I still am getting the same result though.

Could you please direct me to any resources I could use to find more information?

4

I figured out what was going wrong. @bayodesegun pointed out earlier that my project wasn’t getting build properly, which was spot-on. The issue is with my CMakeLists.txt file and my launch file.

To begin with, I am launching the “/trajectory_by_name” service from my current package’s launch file with <include file="$(find trajectory_by_name)/launch/start_service.launch"/>. This isn’t necessary, and I just called the service from the shell ahead of time instead.

Along with this issue, I was also trying to generate the trajectory_by_name_srv/srv/TrajByName.srv file all over again in my package as is reflected in my CMakeLists.txt file. I didn’t need to do this either, because TrajByName has already been generated when we start the “trajectory_by_name” service. I only had to include the “trajectory_by_name_srv” package this new package, and it would have worked out fine.

2 Likes