LCM的安装与使用

LCM（Lightweight Communications and Marshalling）是一套用于消息传递和数据编组的库和工具，针对高带宽和低延迟至关重要的实时系统。 它提供了一个发布/订阅消息传递模型和自动编组/解组代码生成，并为各种编程语言的应用程序提供绑定。
目前版本是1.3.1，下载地址为：https://github.com/lcm-proj/lcm/releases
在Ubuntu下，所依赖的包有：

• build-essential

• libglib2.0-dev

  建议安装的包有：

• openjdk-6-jdk
• python-dev

安装

开启终端依次运行下列代码

$ unzip lcm-1.3.1.zip
$ cd lcm-1.3.1
$ ./configure
$ make
$ sudo make install
$ sudo ldconfig

安装之后

为lcm创建一个ld.so.conf文件：

$ export LCM_INSTALL_DIR=/usr/local/lib
$ echo $LCM_INSTALL_DIR > /etc/ld.so.conf.d/lcm.conf

配置pkgconfig来查找lcm.pc

$ export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:$LCM_INSTALL_DIR/pkgconfig

Python用户需要使用.pth文件将lcm安装位置添加到Python的站点包搜索路径。

$ export PYTHON_VERSION=$(python -c "import sys; print(\"%s.%s\" % sys.version_info[:2])")
$ export PYTHON_USER_SITE=$(python -m site --user-site)
$ echo "$LCM_INSTALL_DIR/python$PYTHON_VERSION/site-packages" > $PYTHON_USER_SITE/lcm.pth

应用教程（C++）

http://lcm-proj.github.io/tut_cpp.html

多播配置1

export LCM_DEFAULT_URL=udpm://239.255.76.67:7667?ttl=1

一个ROS使用LCM例子

#include "ros/ros.h"
#include 
#include 

#include 
#include "exlcm/robot_control_t.hpp"

class Handler 
{
    public:
        ~Handler() {}
        objrecog_msgs::object_id lcmsrv;
        void handleMessage(const lcm::ReceiveBuffer* rbuf,
                const std::string& chan, 
                const robot_control_t* msg)
        {
            printf("Received message on channel \"%s\":\n",chan.c_str());
            printf("Received message 2: \"%d\":\n",msg->iparams[1]);
            printf("Received message 1: \"%d\":\n",msg->iparams[0]);
        if(msg->iparams[0]==1)
            lcmsrv.request.object_id = msg->iparams[1];
        else
        lcmsrv.request.object_id = 0;
        }
};

int main(int argc, char** argv)
{
  ros::init(argc, argv, "this_node_name");
  ros::NodeHandle n;
  ros::ServiceClient client = n.serviceClient("/service_name");
  ros::Rate loop_rate(50);
  lcm::LCM lcm;
  Handler handlerObject;
  lcm.subscribe("SERVICE_COMMAND", &Handler::handleMessage, &handlerObject);

    while (n.ok())
    {
        ros::spinOnce();
        if (!lcm.good()) {
            printf("stop\n");
            break;
        }
        if (lcm.handle() != 0)
            break;
        ROS_INFO("Success,%d",handlerObject.lcmsrv.request.object_id);
    if(handlerObject.lcmsrv.request.object_id !=0)
    {
        if (client.call(handlerObject.lcmsrv))
        {
            ROS_INFO("Success");
        }
        else
  {
    ROS_ERROR("Failed to call service pose");
    return 1;
  }
}
        loop_rate.sleep();
    }

    return 0;
}

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1. http://lcm-proj.github.io/multicast_setup.html ↩