如何使用套接字将Arduino连接到C ++？

Question

我的C ++客户端套接字代码只收集Arduino套接字服务器提供的输出的第一行（我想我可以称之为）。你能告诉我我的C ++代码在哪里出错以及如何修复它吗？如果问题太冗长，请跳到底部的C ++代码。

硬件设置：带有以太网卡（屏蔽）的Arduino Mega和带有Ubuntu 16.04的Intel NUC。这两个设备使用电缆和非管理型交换机连接。

Arduino Side：我开始使用Arduino以太网库中的Web服务器示例，并修改代码，直到我能够收集所有I / O的状态，处理I / O数据，并将结果提供给Web客户端。下图显示了我的Arduino菜肴的HTML快照。

处理套接字服务器端的Arduino代码如下（一切正常，但包括显示所有内容）：

#include <SPI.h>
#include <Ethernet.h>

byte mac[] = {0xBA, 0xDA, 0x55, 0x12, 0x34, 0x56};

IPAddress ip(192, 168, 0, 21);

EthernetServer server(80);

void setup() 
{
  Ethernet.begin(mac, ip);

  // Check for Ethernet hardware present
  if (Ethernet.hardwareStatus() == EthernetNoHardware) 
  {
    Serial.println("Ethernet shield was not found.  Sorry, can't run without hardware.");
   while (true) 
   {
      delay(1); // do nothing, no point running without Ethernet hardware
   }
}

if (Ethernet.linkStatus() == LinkOFF) 
{
    Serial.println("Ethernet cable is not connected.");
}

server.begin();
}

void loop()
{
    //true when there is an incoming connection
   if (client) 
   {
     Serial.println("new client");
     // an http request ends with a blank line
     boolean currentLineIsBlank = true;
     while (client.connected()) 
     {
       if (client.available()) 
       {
          //the next two lines print the client HTTP GET request to serial.
          char c = client.read();
          Serial.write(c);
          // if you've gotten to the end of the line (received a newline
          // character) and the line is blank, the http request has ended,
          // so you can send a reply
          if (c == '\n' && currentLineIsBlank) 
          {
             // send a standard http response header
             client.println("HTTP/1.1 200 OK");
             client.println("Content-Type: text/html");
             client.println("Connection: close");  
             client.println("Refresh: 1");  
             client.println();
             client.println("<!DOCTYPE HTML>");
             client.println("<html>");

             //whole bunch of client.println("...."); to dish out a web page.

              client.println("</html>");
              break;
            }

            if (c == '\n') 
            {
               // you're starting a new line
               currentLineIsBlank = true;
            } else if (c != '\r') 
            {
              // you've gotten a character on the current line
              currentLineIsBlank = false;
            }
         }
      }
     // give the web browser time to receive the data
     //delay(1);
     // close the connection:
     client.stop();
     Serial.println("client disconnected");
  }
}

英特尔NUC与Ubuntu 16.04和C ++ 11：我一直在关注一个教程（https://www.binarytides.com/socket-programming-c-linux-tutorial/）来找出套接字客户端，并从https://www.learncpp.com学习C ++。到目前为止，我可以向Google服务器发送请求并使用我的套接字收集HTML页面，并将HTML打印到终端：

这是我的C ++代码：

#include <iostream> //for std::cout & std::endl
#include<arpa/inet.h> //inet_addr
#include<string.h> // for strlen

int main()
{
    int my_socket = socket(AF_INET , SOCK_STREAM , 0);

    //make sure the socket we got is OK
    if (my_socket == -1)
    {
         std::cout << "problem creating a socket." << std::endl;
    }

    struct sockaddr_in connectionToServer;

    connectionToServer.sin_addr.s_addr = inet_addr("172.217.2.99");//google IP
    connectionToServer.sin_family = AF_INET; //type of IP addres. where AF_INET is IPv4
    connectionToServer.sin_port = htons(80); //port is set via a method


    if (connect(my_socket , (struct sockaddr *)&connectionToServer , sizeof(connectionToServer)) < 0)
    {
        std::cout << "connect error" << std::endl;
        return 1;
    }

    std::cout << "Connected" << std::endl;

    //send a request to get a page
    char *message = "GET / HTTP/1.1\r\n\r\n";
    if( send(my_socket , message , strlen(message) , 0) < 0)
    {
        std::cout << "Send failed" << std::endl;
        return 1;
    }

    std::cout << "Data Sent\n" << std::endl;


    char buffer [20000] = {};
    if( recv(my_socket, buffer , sizeof(buffer) , 0) < 0)
    {
        std::cout << "recv failed" << std::endl;
    }

    for(int i=0; i<20000 ; i++)
    {
        std::cout<< buffer[i];
    }

    return 0;
 }

问题：当我在我的C ++程序中将IP地址从Google更改为我的Arduino时，cpp客户端套接字程序仅收集Arduino套接字服务器输出的第一行。我知道这是第一行，因为我修改了第一行，Arduino服务器通过添加“..但它无关紧要”，并且更改出现在c ++程序的标准输出窗口中。我需要C ++程序来收集整个输出，而不仅仅是第一行。对于我的生活，我无法弄清楚如何。

能否帮我解决以下问题：

如何收集整个Arduino消息（而不仅仅是第一行）？我需要对C ++程序进行哪些修改？系统需要能够将数据从一个设备传递到另一个设备。
此设置的整个目标是将Arduino中的2个浮点数和6个整数传递给我的C ++程序。我很快就会废除整个HTML的东西。你推荐我在传递数据时使用什么样的协议？我在考虑用字母填充每个值。例如：“Aint1A Bint2B Cint3C Dfloat1D ......”等等。你能推荐一些帖子/教程/网页，它建议打包和处理通过套接字到达C ++程序的数据的最佳方法吗？

我提前为'fix-my-codez'问题道歉，但我读到的所有问题对我来说都有点过于先进，因为它们解决了缓冲区溢出，安全性，字节序问题，错误处理，格式错误的消息等问题，超出了我的需求（能力可能更准确）。非常感谢您的时间和帮助。

Answer 1

非常感谢Jonathan Potter和Remy Lebeau在评论中提供了一个有效的答案。我执行了你的建议/答案，一切顺利。我没有触及Arduino代码，并在CPP代码中进行了以下更改：

在问题中的CPP代码中删除（包括）char buffer [20000] = {};中的所有内容并将其替换为：

//***********receive the results**************************
//initialize a string
std::string totalResults;

//create a temp array. This will hold a single line recieved from
//the arduino.
char tempBuffer [300] = {};

//the number of lines I want to recieve from the arduino
int magicNumber = 100;

//recieve the arduino response
for(int i = 0; i < magicNumber ; i++)
{
    //call the recv method over and over as it gets a single arduino line with
    //every iteration.
    if( recv(my_socket, tempBuffer , sizeof(tempBuffer) , 0) < 0)
    {
    std::cout << "recv failed" << std::endl;
    }

    //write out the single line we recieved to a string (which grows on the fly)
    for(int i = 0; i < 300; i++ )
    {
        totalResults = totalResults+tempBuffer[i];

        //kill the loop the moment there is a null character. When i created the
        //array i initialized it with NULL characters. so if I am seeing a null
        //character it means that the data I recieved from the arduino has all been
        //given to the string.
        if(tempBuffer[i] == NULL)
        {
            break;
        }
    }

    //empty array - see: https://stackoverflow.com/questions/632846/clearing-a-char-array-c
    std::fill(&tempBuffer[0], &tempBuffer[300], 0);

}

//print the results to the standard output.
std::cout << totalResults << std::endl;

这些变化（我肯定可以从这里到月球和后面进行评论）使我能够获得arduino发送的数据而不会丢失单个ASCII字符。谢谢！

另请注意，感谢David Schwartz和Remy Lebeau指出我使用的HTTP协议非常糟糕。我使用HTTP，因为我知道它是Arduino代码中的一个工作示例;现在的目标是删除HTML并找到一种更有效的方法将值传递给cpp代码（仅使用套接字）。非常感谢您的评论！

****编辑****

好的，所以如果你还在读这个，你必须使用以太网将一些信息从Arduino传递给cpp程序。如果是这样的话。在我被引导如何接收完整的Arduino响应后，我删除了所有HTML和HTTP，并简单地从Arduino中使用字母填充发送了我需要的值（例如：Aint1B，Cint2D，Efloat1F等等）。我用~~~字符标记了Arduino的传输结束。凉。但是，由于某些原因，有时我会得到整个Arduino响应，有时它会丢失一些消息的尾部。这是我学到的：

recv从中读取的位置（内存或系统调用我不知道）有时只能有一个char值。
有时\n字符都是recv fetches！
有时，recv从中读取的位置可以有多个值！有些时候recv方法返回6个字符，有时它只返回4.这种行为似乎无法预测。

考虑到这种行为，我修改了我的cpp代码。此代码接收整个消息，当它发生时，将停止recv方法的额外不必要的循环。希望你觉得它有用：

//***********receive the results**************************
//initialize a string
std::string totalResults = "";

//create a temp array. This will hold a single line recieved from
//the arduino.
char tempBuffer [300] = {};

//the number of lines I want to receive from the Arduino. This is an unusual
//value for the following reasons (figured out via println):
//(1) sometimes the buffer where the recv method reads from has only one value.
//    ex: letter A only (as per my,*ahem", "protocol".
//(2) sometimes the \n is all a recv fetches!
//(3) sometimes the buffer where the recv method reads has multiple values, so
//    the recv fetches many items that get unpacked in the second loop. This is
//    why sometimes we increase the value by only 1, but get WAY more values. I
//    observed this behaviour to be non repeating. Sometimes it reads 5 values,
//    and sometimes it reads only 3 values.
// At a value of 60 I am always getting the message, and run the recv command
// unnecesserily. For this reason I have implemented the "end transmission"
// characters (~~~), which allow me to kill the for loop once the full message is
// retrieved.
int numberOfTimesRecvRuns = 60;

//number of characters per line. do not reduce as it is needed to be this size to
// get the full insult if the protocol is not followed.
int arduinoNumberOfCharsPerLine = 50;

bool fullResponseRecieved = false;

//recieve the entire arduino response. The magic number is the number of times
// we call the recv method (which reads a line from the socket).
for(int i = 0; i < numberOfTimesRecvRuns; i++)
{
    //call the recv method over and over as it gets a single arduino line with
    //every iteration.
    if( recv(my_socket, tempBuffer , sizeof(tempBuffer) , 0) < 0)
    {
    std::cout << "recv failed" << std::endl;
    }

    //write out the single line we recieved to a string (which grows on the fly). 300 because
    //i dont believe I will have more than 300 characters per line.
    for(int j = 0; j < arduinoNumberOfCharsPerLine; j++ )
    {
        totalResults = totalResults+tempBuffer[j];
        std::cout << "i: " << j << " value recv read: " << tempBuffer[j]<< std::endl;

        //kill the loop the moment there is a null character. When i created the
        //array i initialized it with NULL characters. so if I am seeing a null
        //character it means that the data I recieved from the arduino has all been
        //given to the string.
        if(tempBuffer[j] == NULL )
        {
            std::cout << "I ran... See ya" << std::endl;
            break;
        }

        //end of transmission detected
        if(tempBuffer[j] == '~')
        {
            fullResponseRecieved = true;
        }
    }

    //empty array - see: https://stackoverflow.com/questions/632846/clearing-a-char-array-c
    std::fill(&tempBuffer[0], &tempBuffer[300], 0);

    // A '~' character means the full message has been recieved and there is no
    // need to keep looping for the purpose of running the recv method.
    if(fullResponseRecieved == true)
    {
        //reset the value
        fullResponseRecieved = false;
        std::cout << "killing recv loop" << std::endl;
        break;
    }

}

//print the results to the standard output.
std::cout << totalResults << std::endl;

return 0;

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