Step 1: Create a Custom Service Interface

1. Create a Package for Interfaces: If you haven't already, create a package for your custom interfaces. For example, my_robot_interfaces.

2. Create a Service Interface:

   • Navigate to your package and create a new directory named srv.

   • Inside srv, create a file named Fibonacci.srv.

   • Define the service interface in this file. For example:

     int32 number
     ---
     int32 fibonacci_number
     
     

3. Verify the CMakeLists.txt Configuration Make sure that your CMakeLists.txt file in the my_robot_interfaces package correctly includes the service interface.

rosidl_generate_interfaces(${PROJECT_NAME}
"msg/YourOtherMessages.msg"
"srv/Fibonacci.srv"
)

Step 2: Implement the Service Server

1. Create a Server Node:

   • Create a new Python file in your package's src directory, e.g., fibonacci_server.py.

2. Import Necessary Modules:

   import rclpy
   from rclpy.node import Node
   from my_robot_interfaces.srv import Fibonacci  # Import your custom service interface
   
   

3. Define the Service Server:

   def fibonacci(n):
       if n <= 0:
           return 0
       elif n == 1:
           return 1
       else:
           return fibonacci(n-1) + fibonacci(n-2)
   
   class FibonacciServer(Node):
       def __init__(self):
           super().__init__("fibonacci_server")
           self.fibonacci_service = self.create_service(
               Fibonacci,  # Service interface
               "fibonacci",  # Service name
               self.fibonacci_callback  # Callback function
           )
           self.get_logger().info("Fibonacci Service started")
   
       def fibonacci_callback(self, request, response):
           response.fibonacci_number = fibonacci(request.number)
           self.get_logger().info(f"Fibonacci of {request.number} is {response.fibonacci_number}")
           return response
   
   def main(args=None):
       rclpy.init(args=args)
       node = FibonacciServer()
       rclpy.spin(node)
       rclpy.shutdown()
   
   if __name__ == "__main__":
       main()
   
   

4. Install the Node: Add the following line to your package's setup.py file under entry_points:

   entry_points={
       'console_scripts': [
           # Other scripts...
           "fibonacci_server = my_pkg.fibonacci_server:main"
       ],
   },
   
   

Step 3: Implement the Service Client

1. Create a Client Node:

   • Create a new Python file in your package's src directory, e.g., fibonacci_client.py.

2. Import Necessary Modules:

   import rclpy
   from rclpy.node import Node
   from my_robot_interfaces.srv import Fibonacci  # Import your custom service interface
   
   

3. Define the Service Client:

   class FibonacciClient(Node):
       def __init__(self):
           super().__init__("fibonacci_client")
           self.client = self.create_client(Fibonacci, "fibonacci")  # Service name
           while not self.client.wait_for_service(timeout_sec=1.0):
               self.get_logger().info("Fibonacci Service not available, waiting...")
           self.get_logger().info("Fibonacci Service available")
   
       def send_request(self, number):
           req = Fibonacci.Request()
           req.number = number
           future = self.client.call_async(req)
           while rclpy.ok():
               rclpy.spin_once(self)
               if future.done():
                   try:
                       response = future.result()
                   except Exception as e:
                       self.get_logger().info(f"Service call failed {e}")
                   else:
                       self.get_logger().info(f"Fibonacci of {number} is {response.fibonacci_number}")
                   break
   
   def main(args=None):
       rclpy.init(args=args)
       node = FibonacciClient()
       node.send_request(10)  # Calculate Fibonacci of 10
       rclpy.spin(node)
       rclpy.shutdown()
   
   if __name__ == "__main__":
       main()
   
   

4. Install the Node: Add the following line to your package's setup.py file under entry_points:

   entry_points={
       'console_scripts': [
           # Other scripts...
           "fibonacci_client = my_pkg.fibonacci_client:main"
       ],
   },