ROS2自学笔记：服务_ros2 create service

服务是ROS2一种通信方式，具有以下特点：
1 客户端，服务器模型：不同于话题单向通信，服务可以进行双向通信，客户端发起请求，服务器端进行应答
2 同步通信机制：通信双端同步通信，如果一方无法收到会发送另一端
3 服务端唯一，客户端不唯一：一对多通信
4 .srv文件定义请求和应答数据结构：服务通信消息类型为.srv

示例1 加法计算器
客户端

import sys

import rclpy
from rclpy.node import Node
from learning_interface.src import AddTwoInts 

class adderClient(Node):
	def __init__(self, name):
		super().__init__(name)
		self.client = self.create_client(AddTwoInts, 'add_two_ints')
		while not self.client.wait_for_service(timeout_sec = 1.0):
			self.get_logger().info('service not available, waiting again...')
		self.request = AddTwoInts.Request()

	def send_request(self):
		self.request.a = int(sys.argv[1])
		self.request.b = int(sys.argv[2])
		self.future = self.client.call_async(self.request)

def main(args=None)
	rclpy.init(args=args)
	node = adderClient("service_adder_client")
	node.send_request()

	while rclpy.ok():
		rclpy.spin_once(node)
	
		if node.future.done():
			try: 
				response = node.future.result()
			except Exception as e:
				node.get_logger().info('Service call failed %r' % (e,))
			else:
				node,get_logger().info('Result of add_two_ints: for %d + %d = %d' % (node.request.a, node.request.b, response.sum
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33