ROS版本：indigo
Linux版本：Ubuntu14.04
在開始第一個ROS(Robot Operating System)程序之前，確保已經按照官方教程成功安裝了ROS。本文建立的是一個非常簡單的發佈（Publisher）、訂閱(Subscriber)程序.
一個簡單的發佈（Publisher）、訂閱(Subscriber)程序
寫一個發佈（Publisher）節點
節點（node）是連接到ROS網絡中可執行的基本單元。我們在這創建一個發佈者—“talker”節點，這個節點持續對外發布消息。
首先我們要把目錄切換到我們的beginner_tutorials工程包中。
$ cd ~/catkin_ws/src/beginner_tutorials 因爲我們已經編譯過這個工程包了，所以會在beginner_tutorials文件夾下看到CmakeList.txt、package.xml文件和include、src這兩個目錄。接下來進入src子目錄
$ cd src 在src目錄中創建一個talker.cpp文件，裏面的內容如下：
#include "ros/ros.h"
#include "std_msgs/String.h"
#include <sstream>
int main(int argc, char **argv)
{
/**
* The ros::init() function needs to see argc and argv so that it can perform
* any ROS arguments and name remapping that were provided at the command line. For programmatic
* remappings you can use a different version of init() which takes remappings
* directly, but for most command-line programs, passing argc and argv is the easiest
* way to do it. The third argument to init() is the name of the node.
*
* You must call one of the versions of ros::init() before using any other
* part of the ROS system.
*/
ros::init(argc, argv, "talker");
/**
* NodeHandle is the main access point to communications with the ROS system.
* The first NodeHandle constructed will fully initialize this node, and the last
* NodeHandle destructed will close down the node.
*/
ros::NodeHandle n;
/**
* The advertise() function is how you tell ROS that you want to
* publish on a given topic name. This invokes a call to the ROS
* master node, which keeps a registry of who is publishing and who
* is subscribing. After this advertise() call is made, the master
* node will notify anyone who is trying to subscribe to this topic name,
* and they will in turn negotiate a peer-to-peer connection with this
* node. advertise() returns a Publisher object which allows you to
* publish messages on that topic through a call to publish(). Once
* all copies of the returned Publisher object are destroyed, the topic
* will be automatically unadvertised.
*
* The second parameter to advertise() is the size of the message queue
* used for publishing messages. If messages are published more quickly
* than we can send them, the number here specifies how many messages to
* buffer up before throwing some away.
*/
ros::Publisher chatter_pub = n.advertise<std_msgs::String>("chatter", 1000);
ros::Rate loop_rate(10);
/**
* A count of how many messages we have sent. This is used to create
* a unique string for each message.
*/
int count = 0;
while (ros::ok())
{
/**
* This is a message object. You stuff it with data, and then publish it.
*/
std_msgs::String msg;
std::stringstream ss;
ss << "hello world " << count;
msg.data = ss.str();
ROS_INFO("%s", msg.data.c_str());
/**
* The publish() function is how you send messages. The parameter
* is the message object. The type of this object must agree with the type
* given as a template parameter to the advertise<>() call, as was done
* in the constructor above.
*/
chatter_pub.publish(msg);
ros::spinOnce();
loop_rate.sleep();
++count;
}
return 0;
} 寫一個訂閱（Subscriber）節點
還是在src目錄下，創建一個listener.cpp文件。內容如下：
#include "ros/ros.h"
#include "std_msgs/String.h"
/**
* This tutorial demonstrates simple receipt of messages over the ROS system.
*/
void chatterCallback(const std_msgs::String::ConstPtr& msg)
{
ROS_INFO("I heard: [%s]", msg->data.c_str());
}
int main(int argc, char **argv)
{
/**
* The ros::init() function needs to see argc and argv so that it can perform
* any ROS arguments and name remapping that were provided at the command line. For programmatic
* remappings you can use a different version of init() which takes remappings
* directly, but for most command-line programs, passing argc and argv is the easiest
* way to do it. The third argument to init() is the name of the node.
*
* You must call one of the versions of ros::init() before using any other
* part of the ROS system.
*/
ros::init(argc, argv, "listener");
/**
* NodeHandle is the main access point to communications with the ROS system.
* The first NodeHandle constructed will fully initialize this node, and the last
* NodeHandle destructed will close down the node.
*/
ros::NodeHandle n;
/**
* The subscribe() call is how you tell ROS that you want to receive messages
* on a given topic. This invokes a call to the ROS
* master node, which keeps a registry of who is publishing and who
* is subscribing. Messages are passed to a callback function, here
* called chatterCallback. subscribe() returns a Subscriber object that you
* must hold on to until you want to unsubscribe. When all copies of the Subscriber
* object go out of scope, this callback will automatically be unsubscribed from
* this topic.
*
* The second parameter to the subscribe() function is the size of the message
* queue. If messages are arriving faster than they are being processed, this
* is the number of messages that will be buffered up before beginning to throw
* away the oldest ones.
*/
ros::Subscriber sub = n.subscribe("chatter", 1000, chatterCallback);
/**
* ros::spin() will enter a loop, pumping callbacks. With this version, all
* callbacks will be called from within this thread (the main one). ros::spin()
* will exit when Ctrl-C is pressed, or the node is shutdown by the master.
*/
ros::spin();
return 0;
} 編譯創建的節點
在編譯我們創建的節點之前，我們還需要編輯Cmakelist.txt文件（注意：是beginner_tutorials項目包下的CMakelist文件），告訴編輯器我們需要編輯什麼文件，需要什麼依賴。
$ gedit CMakeLists.txt在文件末尾添加如下語句：
include_directories(include ${catkin_INCLUDE_DIRS})
add_executable(talker src/talker.cpp)
target_link_libraries(talker ${catkin_LIBRARIES})
add_dependencies(talker beginner_tutorials_generate_messages_cpp)
add_executable(listener src/listener.cpp)
target_link_libraries(listener ${catkin_LIBRARIES})
add_dependencies(listener beginner_tutorials_generate_messages_cpp)
將目錄切換到工作區目錄，並執行catkin_make運行命令：
$ cd ~/catkin_ws
$ catkin_make 不出意外的話，會出現如下界面：
至此，程序已經創建完成，而接下來我們要檢查一下我們創建的程序是否正確。
測試程序的正確性
首先，我們得要啓動ROS核心程序roscore。
$ roscore 在使用我們的程序之前，需要先把程序註冊
$ cd ~/catkin_ws
$ source ./devel/setup.bash運行talker節點：
$ rosrun beginner_tutorials talker在另一個終端下運行listener節點：
$ rosrun beginner_tutorials listener （注意：在運行listener節點時應再把程序註冊一遍，即
$ cd ~/catkin_ws
$ source ./devel/setup.bash）
這時候會看到如下信息：
如圖能看見發佈和訂閱的節點正在正常運行。一個在發送一個在接收。
這說明訂閱節點（listener）已經成功的接收到了發佈節點（talker）發佈的信息。至此，整個程序結束！