跨平臺c++/boost/asio 簡單的HTTP POST請求 客戶端模型

冷侃發表於2015-12-09
C++HTTP客戶端模型

作為一個呼應，寫一個c++版本的同步http post客戶端功能，如果你需要純C版本，移步這裡

linux下純C簡單的HTTP POST請求 客戶端模型

講解一下基本的的http post協議

  • 通過\r\n，實現tcp的訊息邊界
  • 每個請求的第一段 POST /a.b HTTP/1.1
    • POST http的方法，還有最常用的GET，當然還有其他的幾種，略過
    • /a.b 請求的網頁路徑，比如如果是首頁，最經常的就是/
    • HTTP/1.1 http協議的版本號,傳說中已經出了2了，還有神奇的谷歌出的用來替代http協議的SPDY
  • 通過這條資訊表明這是一個表單
    • Content-Type: application/x-www-form-urlencoded
  • 通過這條資訊來表示這次httppost 的包體長度，非必需項
    • Content-Length:12
  • 然後就是一個空行，代表接下來都是包體

剛才是請求，談一下響應就更簡單了

  • 響應內容 HTTP/1.1 200 OK
    • 200就是傳送中的狀態，404沒找喔等等
    • HTTP/1.1 表示http的版本號
    • 當然，如果包頭也是可以存在，此處不介紹
    • 然後就是一個空行，分割是包體

好了，直接上程式碼吧

#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存在複用的情況
    if(io_service.stopped())
      io_service.reset();

    // 從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);
    
    // 嘗試連線到其中的某個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;
    }
    // 如果伺服器返回非200都認為有錯,不支援301/302等跳轉
    if (status_code != 200)
    {
      reponse_data = "Response returned with status code != 200 " ;
      return status_code;
    }

    // 傳說中的包頭可以讀下來了
    std::string header;
    std::vector<string> headers;        
    while (std::getline(response_stream, header) && header != "\r")
      headers.push_back(header);

    // 讀取所有剩下的資料作為包體
    boost::system::error_code error;
    while (boost::asio::read(socket, response,
        boost::asio::transfer_at_least(1), error))
    {           
    }

    //響應有資料
    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;
}

編譯一下吧。。

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

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