ROS Service

A service is a node that must run and you must wait until it has completed.

Commands

rosservice list
rosservice info <service name>  # Node, URI, Type and Args
rossrv show <service name>      # Args and return type
rosservice call <service name> <args> # "{}" is empty arg

Python Call ROS Service

import rospy
from gazebo_msgs.srv import DeleteModel, DeleteModelRequest
import sys

rospy.init_node('service_client')
rospy.wait_for_service('/gazebo/delete_model')              # Wait for the service client to be running
delete_model_service = rospy.ServiceProxy('/gazebo/delete_model', DeleteModel)  # Create the connection to the service
kk = DeleteRequest()
kk.model_name = "bowl_1"    # Create an Arg for the service
result = delete_model_service(kk)
print(result)

Python Create an ROS Service

import rospy
from std_srvs.srv import Empty, EmptyResponse

def my_callback(request):
    print "My_callback has been called"
    return EmptyResponse()
    #return MyServiceResponse(len(request.words.split()))

rospy.init_node('service_server')
my_service = rospy.Service('/my_service', Empty, my_callback)
rospy.spin()    # maintain the service open

Call Service

rosservice call /my_service "{}"

Create a Catkin Service Project

Create Project

roscd 
cd ../src/
catkin_create_pkg my_custom_srv_msg_pkg rospy
roscd my_custom_srv_msg_pkg
mkdir srv
vim srv/MyCustomServiceMessage.srv

Create Service File

Service file containing the arguments and return type.

float64 radius
int32 repititions
---
bool success

Modify CMakeList.txt and Package.xml

CMakeList.txt

find_package(catkin REQUIRED COMPONENTS
    std_msgs
    message_generation
)

add_service_files(
    FILES 
    MyCustomServiceMessage.srv
)

catkin_package(
    CATKIN_DEPENDS 
    rospy
)

Uncomment area

generate_messages(
    DEPENDENCIES 
    std_msgs
)

Package.xml

Add Lines

<build_depend>message_generation</build_depend>
<run_depend>message_runtime</run_depend>

Build Project

roscd;cd ..
catkin_make
source devel/setup.bash

Test Project

rossrv list | grep MyCustomServiceMessage
rossrv show my_custom_srv_msg_pkg/MyCustomServiceMessage

More Details