跨平台c++/boost/asio 简单的HTTP POST请求 客户端模型

作为一个呼应，写一个c++版本的同步http post客户端功能，如果你需要纯C版本，移步这里

linux下纯C简单的HTTP POST请求 客户端模型

讲解一下基本的的http post协议

• 通过\r\n，实现tcp的消息边界
• 每个请求的第一段 POST /a.b HTTP/1.1
  • POST http的方法，还有最常用的GET，当然还有其他的几种，略过
  • /a.b 请求的网页路径，比如如果是首页，最经常的就是/
  • HTTP/1.1 http协议的版本号,传说中已经出了2了，还有神奇的谷歌出的用来替代http协议的SPDY
• 通过这条信息表明这是一个表单
  • Content-Type: application/x-www-form-urlencoded
• 通过这条信息来表示这次httppost 的包体长度，非必需项
• Content-Length:12
• 然后就是一个空行，代表接下来都是包体

刚才是请求，谈一下响应就更简单了

• 响应内容 HTTP/1.1 200 OK
  • 200就是传送中的状态，404没找喔等等
  • HTTP/1.1 表示http的版本号
  • 当然，如果包头也是可以存在，此处不介绍
  • 然后就是一个空行，分割是包体

好了，直接上代码吧

#include <iostream>
#include <istream>
#include <ostream>
#include <string>
#include <boost/asio.hpp>

using boost::asio::ip::tcp;
using std::string;

int post(const string& host, const string& port, const string& page, const string& data, string& reponse_data)
{
  try
  {
    boost::asio::io_service io_service;
    //如果io_service存在复用的情况
    if(io_service.stopped())
      io_service.reset();

    // 从dns取得域名下的所有ip
    tcp::resolver resolver(io_service);
    tcp::resolver::query query(host, port);
    tcp::resolver::iterator endpoint_iterator = resolver.resolve(query);
    
    // 尝试连接到其中的某个ip直到成功 
    tcp::socket socket(io_service);
    boost::asio::connect(socket, endpoint_iterator); 

    // Form the request. We specify the "Connection: close" header so that the
    // server will close the socket after transmitting the response. This will
    // allow us to treat all data up until the EOF as the content.
    boost::asio::streambuf request;
    std::ostream request_stream(&request);
    request_stream << "POST " << page << " HTTP/1.0\r\n";
    request_stream << "Host: " << host << ":" << port << "\r\n";
    request_stream << "Accept: */*\r\n";
    request_stream << "Content-Length: " << data.length() << "\r\n";
    request_stream << "Content-Type: application/x-www-form-urlencoded\r\n";
    request_stream << "Connection: close\r\n\r\n";
    request_stream << data;

    // Send the request.
    boost::asio::write(socket, request);

    // Read the response status line. The response streambuf will automatically
    // grow to accommodate the entire line. The growth may be limited by passing
    // a maximum size to the streambuf constructor.
    boost::asio::streambuf response;
    boost::asio::read_until(socket, response, "\r\n");

    // Check that response is OK.
    std::istream response_stream(&response);
    std::string http_version;
    response_stream >> http_version;
    unsigned int status_code;
    response_stream >> status_code;
    std::string status_message;
    std::getline(response_stream, status_message);
    if (!response_stream || http_version.substr(0, 5) != "HTTP/")
    {
      reponse_data = "Invalid response";
      return -2;
    }
    // 如果服务器返回非200都认为有错,不支持301/302等跳转
    if (status_code != 200)
    {
      reponse_data = "Response returned with status code != 200 " ;
      return status_code;
    }

    // 传说中的包头可以读下来了
    std::string header;
    std::vector<string> headers;        
    while (std::getline(response_stream, header) && header != "\r")
      headers.push_back(header);

    // 读取所有剩下的数据作为包体
    boost::system::error_code error;
    while (boost::asio::read(socket, response,
        boost::asio::transfer_at_least(1), error))
    {           
    }

    //响应有数据
    if (response.size())
    {
      std::istream response_stream(&response);
      std::istreambuf_iterator<char> eos;
      reponse_data = string(std::istreambuf_iterator<char>(response_stream), eos);                        
    }

    if (error != boost::asio::error::eof)
    {
      reponse_data = error.message();
      return -3;
    }
  }
  catch(std::exception& e)
  {
    reponse_data = e.what();
      return -4;  
  }
  return 0;
}

int main(int argc, char* argv[])
{
  string host = "127.0.0.1";   
  string port = "80";
  string page = "/auth/login";
  string data = "user_name=linbc&password=a";
  string reponse_data;

  int ret = post(host, port, page, data, reponse_data);
  if (ret != 0)
    std::cout << "error_code:" << ret << std::endl;

  std::cout << reponse_data << std::endl;

  return 0;
}

编译一下吧。。

g++ post.cc -std=c++11 -pthread -lboost_system