使用curl c++发送电子邮件

Question

我试着用curl c++发送电子邮件，我很好地登录了，当我运行程序时，它运行良好，不会抛出任何错误，但电子邮件永远不会来。

这是我的密码：

#include <iostream>
#include <curl/curl.h>

static const char *payload_text =
  "Date: Mon, 29 Nov 2010 21:54:29 +1100\r\n"
  "To: " "mailto" "\r\n"
  "From: " "mymail" "\r\n"
  "Message-ID: <dcd7cb36-11db-487a-9f3a-e652a9458efd@"
  "rfcpedant.example.org>\r\n"
  "Subject: SMTP example message\r\n"
  "\r\n" /* empty line to divide headers from body, see RFC5322 */
  "The body of the message starts here.\r\n"
  "\r\n"
  "It could be a lot of lines, could be MIME encoded, whatever.\r\n"
  "Check RFC5322.\r\n";

size_t read_function(char *buffer, size_t size, size_t nmemb,char *data)
{
    size_t len;
    if(size == 0 or nmemb == 0)
    {
        return 0;
    }
    if(data)
    {
        len = strlen(data);
        memcpy(buffer, data, len);
        return len;
    }
    return 0;  
}

int main()
{
    CURL *curl;
    CURLcode res = CURLE_OK;
    const char *data = payload_text;
 
    curl = curl_easy_init();
    if(curl) 
    {
        curl_easy_setopt(curl, CURLOPT_USERNAME, "mymail"); 
        curl_easy_setopt(curl, CURLOPT_PASSWORD, "password");
        curl_easy_setopt(curl, CURLOPT_URL, "smtp://smtp.gmail.com:587");
        curl_easy_setopt(curl, CURLOPT_MAIL_FROM, "my mail");
        curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, "mailto");
        curl_easy_setopt(curl, CURLOPT_READDATA,payload_text);
        curl_easy_setopt(curl, CURLOPT_READFUNCTION, read_function);
        curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
        curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
        curl_easy_setopt(curl, CURLOPT_USE_SSL, CURLUSESSL_ALL);
    }
    res = curl_easy_perform(curl);
    
    if(res != CURLE_OK)
    {
        fprintf(stderr, "curl_easy_perform() failed: %s\n",
        curl_easy_strerror(res));
        curl_easy_cleanup(curl);
    }
    return 0;
}

我认为问题在于卷曲选项READDATA和READUNCTION。在文档中，您必须将数据指针作为参数传递给READDATA。const char *data = payload_text;是数据指针，对吗？

然后，READFUNCTION将返回数据大小的函数作为参数，我认为这就是size_t read_function(char *buffer, size_t size, size_t nmemb,char *data)正在做的事情。

我是新来的，所以任何建议都会对我有好处。

Answer 1

我发现这是一个有用的起点：https://curl.se/libcurl/c/smtp-mail.html

代码有两个主要问题：

1. 您的read_function没有跟踪读取了多少有效负载，所以它会不断地给出相同的内容，反复地胡言乱语，永远不会发出消息的结束信号。
2. 您将CURLOPT_MAIL_RCPT设置为一个字符串，而实际上它应该是一个struct curl_slist *，因为可以有多个收件人。

这是一个固定的例子，我在我的电脑上测试了它的工作。在投递之前，修改了文件顶部的私有数据。

#define USERNAME "david"
#define PASSWORD "xxxxx"
#define MAILTO "david@example.com"
#define MAILFROM "you@example.com"
#define SMTP "smtp://your.smtp.server.example.com:25"

#include <stdio.h>
#include <curl/curl.h>

const char * payload_text =
  "Date: Mon, 29 Nov 2010 21:54:29 +1100\r\n"
  "To: " MAILTO "\r\n"
  "From: " MAILFROM "\r\n"
  "Subject: SMTP example message with libcurl 6\r\n"
  "\r\n"
  "Hello world!\r\n";

struct ReadData
{
  explicit ReadData(const char * str)
  {
    source = str;
    size = strlen(str);
  }

  const char * source;
  size_t size;
};

size_t read_function(char * buffer, size_t size, size_t nitems, ReadData * data)
{
  size_t len = size * nitems;
  if (len > data->size) { len = data->size; }
  memcpy(buffer, data->source, len);
  data->source += len;
  data->size -= len;
  return len;
}

int main()
{
  CURL * curl = curl_easy_init();
  if (!curl)
  {
    fprintf(stderr, "curl_easy_init failed\n");
    return 1;
  }

  curl_easy_setopt(curl, CURLOPT_USERNAME, USERNAME);
  curl_easy_setopt(curl, CURLOPT_PASSWORD, PASSWORD);
  curl_easy_setopt(curl, CURLOPT_URL, SMTP);
  curl_easy_setopt(curl, CURLOPT_MAIL_FROM, MAILFROM);

  struct curl_slist * rcpt = NULL;
  rcpt = curl_slist_append(rcpt, MAILTO);
  curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, rcpt);

  ReadData data(payload_text);
  curl_easy_setopt(curl, CURLOPT_READDATA, &data);
  curl_easy_setopt(curl, CURLOPT_READFUNCTION, read_function);

  curl_easy_setopt(curl, CURLOPT_VERBOSE, 1);
  curl_easy_setopt(curl, CURLOPT_UPLOAD, 1);
  curl_easy_setopt(curl, CURLOPT_USE_SSL, CURLUSESSL_ALL);

  // If your server doesn't have a proper SSL certificate:
  curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0);

  CURLcode res = curl_easy_perform(curl);
  if (res != CURLE_OK)
  {
    fprintf(stderr, "curl_easy_perform() failed: %s\n",
      curl_easy_strerror(res));
    curl_easy_cleanup(curl);
  }
  return 0;
}

Answer 2

read_function：您正在更改不影响调用方字节缓冲区的本地指针buffer。您应该将数据复制到指定的缓冲区。

memcpy(buffer, data, len);

FYI sizeof(char)保证为1，因此不需要。

另一个问题-函数从不返回信号所有数据被发送的0，它一次又一次地发送相同的数据。您应该在第二个电话中返回0。或将长度设置为选项CURLOPT_POSTFIELDSIZE_LARGE。

参见示例smtp-mail.c