增强ASIO HTTP客户端开机自检

我正在尝试让Boost ASIO库发送POST，但变量从未到达服务器。我知道服务器工作正常(使用cURL进行了测试)

此代码不起作用(变量msg未发送到服务器)，但当我使用cURL时它确实起作用

tcp::resolver resolver(io_service);
tcp::resolver::query query("localhost",  "3000"); // "http");
tcp::resolver::iterator endpoint_iterator = resolver.resolve(query);
tcp::resolver::iterator end;

tcp::socket socket(io_service);
boost::system::error_code error = boost::asio::error::host_not_found;
while (error && endpoint_iterator != end)
{
  socket.close();
  socket.connect(*endpoint_iterator++, error);
}
if (error)
  throw boost::system::system_error(error);

boost::asio::streambuf request;
std::ostream request_stream(&request);

string sToSend = "msg=testing";

request_stream << "POST / HTTP/1.1
";
request_stream << "Host: " << "localhost:3000" << "
";
request_stream << "Accept: */*
";
request_stream << "Content-Length: " <<  sToSend.length() << "
";
request_stream << "Content-Type: application/x-www-form-urlencoded";
request_stream << "Connection: close

"; d
request_stream << sToSend;

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

boost::asio::streambuf response;
boost::asio::read_until(socket, response, "
");

要测试我使用的服务器

$ curl --verbose -X POST -d msg=testing123 localhost:3000/
* Hostname was NOT found in DNS cache
*   Trying 127.0.0.1...
* Connected to localhost (127.0.0.1) port 3000 (#0)
> POST / HTTP/1.1
> User-Agent: curl/7.35.0
> Host: localhost:3000
> Accept: */*
> Content-Length: 14
> Content-Type: application/x-www-form-urlencoded
> 
* upload completely sent off: 14 out of 14 bytes
< HTTP/1.1 200 OK
< X-Powered-By: Express
< Date: Mon, 21 Mar 2016 20:55:00 GMT
< Connection: keep-alive
< Transfer-Encoding: chunked
< 
* Connection #0 to host localhost left intact

---

解决方案

此行缺少回车符和换行符：

request_stream << "Content-Type: application/x-www-form-urlencoded";