Use YARP to talk to ROS services

Please see "example/ros" in the YARP source code for full examples.

For simple cases, we can just use YARP Bottles whose content matches ROS types structurally. For example, to call a ROS service that adds two integers, we could do this:

/*
 * Copyright (C) 2006-2020 Istituto Italiano di Tecnologia (IIT)
 * All rights reserved.
 *
 * This software may be modified and distributed under the terms of the
 * BSD-3-Clause license. See the accompanying LICENSE file for details.
 */
 
#include <yarp/os/Bottle.h>
#include <yarp/os/LogComponent.h>
#include <yarp/os/Network.h>
#include <yarp/os/Node.h>
#include <yarp/os/RpcClient.h>
 
using yarp::os::Bottle;
using yarp::os::Network;
using yarp::os::Node;
using yarp::os::RpcClient;
 
namespace {
YARP_LOG_COMPONENT(CLIENT_V2, "yarp.example.ros.add_int_client_v2")
}
 
int main(int argc, char* argv[])
{
    if (argc != 3) {
        yCError(CLIENT_V2, "Call as %s X Y", argv[0]);
        return 1;
    }
 
    Network yarp;
    Node node("/yarp_add_int_client");
 
    RpcClient client;
    if (!client.open("add_two_ints")) {
        yCError(CLIENT_V2, "Failed to open client");
        return 1;
    }
 
    Bottle msg;
    Bottle reply;
    msg.addInt32(atoi(argv[1]));
    msg.addInt32(atoi(argv[2]));
    if (!client.write(msg, reply)) {
        yCError(CLIENT_V2, "Failed to call service");
        return 1;
    }
    yCInfo(CLIENT_V2, "Got %d\n", reply.get(0).asInt32());
 
    return 0;
}

An example CMakeLists.txt file to compile this and link with YARP would be:

cmake_minimum_required(VERSION 3.12)
find_package(YARP COMPONENTS os REQUIRED)
add_executable(add_int_client_v1)
target_sources(add_int_client_v1 PRIVATE add_int_client_v1.cpp)
target_link_libraries(add_int_client_v1 PRIVATE YARP::YARP_os
                                                YARP::YARP_init)

On the ROS side we'd do:

rosrun rospy_tutorials add_two_ints_server

Then on the YARP side we can try it out (assume the above program is compiled as 'add_int_client_v1'):

./add_int_client_v1 4 6

yarp: Port /yarp_add_int_client active at tcp://192.168.1.2:35731
yarp: Port /add_two_ints+1@/yarp_add_int_client active at tcp://192.168.1.2:35004
Got 10