1.配置准备

输入sudo apt-get install ros-$ROS_DISTRO-turtlesim下载安装turtlesim测试包，完成后首先运行roscore
再打开一个终端输入rosrun turtlesim turtlesim_node，不出意外的话会出现一只乌龟
再另外一个终端输入rosrun turtlesim turtle_teleop_key
可以通过上下左右键控制乌龟运动了

2.多机通讯

想在PC上直接按键控制树莓派上的乌龟运动，要如何操作呢？
主机与树莓派信息如下:

Item	IP	Hostname
PC	`192.168.31.111`	`robot-dekstop`
树莓派	`192.168.31.107`	`pi-desktop`

相互ip可以通，因为未添加hostname ip映射，相互无法通过hostname联系

1. 在树莓派上运行roscore和启动turtlesim_node
1. PC上想要与之通讯首先必须设置ROS_MASTER_URI,export ROS_MASTER_URI='http:192.168.31.107:11311'即可，在PC中断输入rostopic
  list即可看到当前的所有topic列表，说明PC已经可以与ROS_MASTER建立通讯了
1. 这时PC端启动rosrun turtlesim turtle_teleop_key无法控制乌龟运动，为什么呢？这里明明rostopic明明可以看到/turtle/cmd_vel。键入rostopic info /turtle/cmd_vel 显示如下
  
  这就明显了,主机从master里面取到的node发送/订阅的topic信息，node地址为http://pi-desktop:46395, PC根本不认识pi-desktop为何物，自然无法发送数据。
1. 如何修改？自然有2个方法：
  - 这个我不认识换个我认识的来，修改树莓派端的ROS_IP环境变量 export ROS_IP=192.168.31.107
    再次查看topic信息，
    
    ，现在就认识了，启动rosrun turtlesim turtle_teleop_key节点，发现仍然无法控制。问题是我认识你，可是你不认我啊，所有本地PC也需要export ROS_IP=192.168.31.111,现在就正常了
  - 这个我不认识，我现在认识下不就行了，PC端修改/etc/hosts 添加一个192.168.31.107 pi-desktop,同时树莓派端一样修改/etc/hosts 添加 192.168.31.111 robot-desktop

3.PIBOT配置

PIBOT相关配置如下

ROS主机(树莓派等)

source /opt/ros/indigo/setup.bash
LOCAL_IP=`hostname -I`
export ROS_IP=`echo $LOCAL_IP`
export ROS_HOSTNAME=`echo $LOCAL_IP`
export PIBOT_MODEL=apollo
export PIBOT_LIDAR=rplidar
export ROS_MASTER_URI=`echo http://$ROS_IP:11311`
source ~/pibot_ros/ros_ws/devel/setup.bash

source /opt/ros/indigo/setup.bash
LOCAL_IP=`hostname -I`
export ROS_IP=`echo $LOCAL_IP`
export ROS_HOSTNAME=`echo $LOCAL_IP`
export PIBOT_MODEL=apollo
export PIBOT_LIDAR=rplidar
export ROS_MASTER_URI=`echo http://xxx.xxx.xx.xx:11311`
source ~/pibot_ros/ros_ws/devel/setup.bash

xxx.xxx.xx.xx为ROS主机IP

4. 总结

多机通讯只能有一个master存在，所有都设置ROS_MASTER_URI为http://MASTER_IP:11311, 各个终端要能相互通讯就必须设置自己的ROS_IP。

5. 一键配置脚本

PIBOT提供一键配置脚本，只需要根据提示输入即可配置上面参数

#!/bin/bash
if [ ! -z "$PIBOT_HOME" ]; then
    PIBOT_HOME_DIR=$PIBOT_HOME
else
    PIBOT_HOME_DIR=~/pibot_ros
fi


code_name=$(lsb_release -sc)

if [ "$code_name" = "trusty" ]; then
    ros_version="indigo"
elif [ "$code_name" = "xenial" ]; then
    ros_version="kinetic"
elif [ "$code_name" = "bionic" ] || [ "$code_name" = "stretch" ]; then
    ros_version="melodic"
else
    echo -e "\033[1;31m PIBOT not support "$code_name"\033[0m"
    exit
fi 


content="#!/bin/bash
#source ros
if [ ! -f /opt/ros/${ros_version}/setup.bash ]; then 
    echo \"please run cd $PIBOT_HOME_DIR && ./pibot_install_ros.sh to install ros sdk\"
else
    source /opt/ros/${ros_version}/setup.bash
fi
"
echo "${content}" > ~/.pibotrc

#LOCAL_IP=`ifconfig eth0|grep "inet addr:"|awk -F":" '{print $2}'|awk '{print $1}'`
#LOCAL_IP=`ip addr | grep 'state UP' -A2 | tail -n1 | awk '{print $2}' | awk -F"/" '{print $1}'`

#if [ ! ${LOCAL_IP} ]; then
#    echo "please check network"
#    exit
#fi

LOCAL_IP=`ip addr | grep 'state UP' -A2 | tail -n1 | awk '{print $2}' | awk -F"/" '{print $1}'`
echo "LOCAL_IP=\`ip addr | grep 'state UP' -A2 | tail -n1 | awk '{print \$2}' | awk -F"/" '{print \$1}'\`" >> ~/.pibotrc

if [ ! ${LOCAL_IP} ]; then
    echo -e "\033[1;31muse 127.0.0.1 as local ip\033[0m"
    LOCAL_IP=127.0.0.1
fi


echo "export ROS_IP=\`echo \$LOCAL_IP\`" >> ~/.pibotrc
echo "export ROS_HOSTNAME=\`echo \$LOCAL_IP\`" >> ~/.pibotrc

echo -e "\033[1;34mplease specify the current machine(ip:$LOCAL_IP) type:\033[1;32m
                        (0: pibot board,
                        \033[31m1: control PC or Virtual PC\033[1;34m)\033[1;33m" 
read PIBOT_INPUT
if [ "$PIBOT_INPUT" = "0" ]; then
    ROS_MASTER_IP_STR="\`echo \$LOCAL_IP\`"
    ROS_MASTER_IP=`echo $LOCAL_IP`
else
    echo -e "\033[1;34mplase specify the pibot board ip for commnication(e.g. 192.168.12.1):" 
    read -p "" PIBOT_INPUT
    ROS_MASTER_IP_STR=`echo $PIBOT_INPUT`
    ROS_MASTER_IP=`echo $PIBOT_INPUT`
fi

echo "export ROS_MASTER_URI=`echo http://${ROS_MASTER_IP_STR}:11311`" >> ~/.pibotrc

echo -e "\033[1;35m*****************************************************************"
echo "local_ip:     " ${LOCAL_IP} 
echo "onboard_ip:   " ${ROS_MASTER_IP}
echo ""
echo -e "please execute \033[1;36;4msource ~/.bashrc\033[1;35m to make the configure effective\033[0m"
echo -e "\033[1;35m*****************************************************************\033[0m"

复制上面脚本保存至文件init_env.sh,执行bash init_env.sh, 按照提示输入

init_env.gif

树莓派输入0，会自动读取树莓派ip，写入变量至~/.piborc文件
PC端输入1，再次输入树莓派的ip，写入变量至~/.piborc文件

source ~/.piborc当次生效或使用下面命令写入到bash的环境变量中

echo "source ~/.piborc" >> ~/.bashrc

ROS多机的通讯配置