我正在尝试实现一个 C++ 服务器来为 javascript EventSource 生成事件,我正在使用 cpprest 构建它。从我在 PHP 或 Node.js 中看到的示例来看,它看起来非常简单,但我一定错过了一些东西,因为我在 Firefox 控制台中得到了这个:
Firefox can’t establish a connection to the server at http://localhost:32123/data.
使用邮递员,我正确接收了
"data : test"
,所以我认为我错过了一些延续,可能需要做的不仅仅是回复请求,但我没有找到关于这应该如何进行的良好解释还没工作呢。如果您有一些文档可以指出我,我将不胜感激!
html页面脚本如下所示:
var source = new EventSource("http://localhost:32123/data");
source.onmessage = function (event) {
document.getElementById("result1").innerHTML += event.data + "<br>";
};
C++ 服务器响应:
wResponse.set_status_code(status_codes::OK);
wResponse.headers().add(U("Access-Control-Allow-Origin"), U("*"));
wResponse.set_body(U("data: test"));
iRequest.reply(wResponse);
我的服务器收到的请求:
GET /data HTTP/1.1
Accept: text/event-stream
Accept-Encoding: gzip, deflate
Accept-Language: en-us, en;q=0.5
Cache-Control: no-cache
Connection: keep-alive
Host: localhost:32123
Origin: null
Pragma: no-cache
User-Agent: Mozilla/5.0 (Windows NT6.1; Win64, x64; rv:61.0) Gecko/20100101 Firefox/61.0
这是一个小证明。它一点也不完美,但它正在发挥作用。下一步是弄清楚如何存储连接,检查它们是否处于活动状态,等等......
编辑:在达伦评论后更新答案
正确的解决方案似乎是围绕将
producer_consumer_buffer<char>
喂给绑定到设置为 basic_istream<uint8_t>
主体的 http_response
来展开。
然后,一旦
http_request::reply
完成,连接将保持打开状态,直到缓冲区关闭,这可以通过 wBuffer.close(std::ios_base::out).wait();
完成。
我不是 100% 确定,但似乎
wBuffer.sync().wait();
的作用就像 PHP flush
命令将在类似的 event-providing-server 场景中使用。
下面添加了一个工作示例。
显然这不是一个完整的解决方案。管理连接等方面还有更多乐趣。用
Connection
实例化一些 make_unique
并将它们存储到事件访问的容器中可能是我的方法......
main.cpp
#include "cpprest/uri.h"
#include "cpprest/producerconsumerstream.h"
#include "cpprest/http_listener.h"
using namespace std;
using namespace web;
using namespace http;
using namespace utility;
using namespace concurrency;
using namespace http::experimental::listener;
struct MyServer
{
MyServer(string_t url);
pplx::task<void> open() { return mListener.open(); };
pplx::task<void> close() { return mListener.close(); };
private:
void handleGet(http_request iRequest);
http_listener mListener;
};
MyServer::MyServer(utility::string_t url) : mListener(url)
{
mListener.support(methods::GET, bind(&MyServer::handleGet, this, placeholders::_1));
}
void MyServer::handleGet(http_request iRequest)
{
ucout << iRequest.to_string() << endl;
http_response wResponse;
// Setting headers
wResponse.set_status_code(status_codes::OK);
wResponse.headers().add(header_names::access_control_allow_origin, U("*"));
wResponse.headers().add(header_names::content_type, U("text/event-stream"));
// Preparing buffer
streams::producer_consumer_buffer<char> wBuffer;
streams::basic_istream<uint8_t> wStream(wBuffer);
wResponse.set_body(wStream);
auto wReplyTask = iRequest.reply(wResponse);
wBuffer.putn_nocopy("data: a\n",10).wait();
wBuffer.putn_nocopy("data: b\n\n",12).wait();
wBuffer.sync().wait(); // seems equivalent to 'flush'
this_thread::sleep_for(chrono::milliseconds(2000));
wBuffer.putn_nocopy("data: c\n", 10).wait();
wBuffer.putn_nocopy("data: d\n\n", 12).wait();
wBuffer.sync().wait();
// wBuffer.close(std::ios_base::out).wait(); // closes the connection
wReplyTask.wait(); // blocking!
}
unique_ptr<MyServer> gHttp;
void onInit(const string_t iAddress)
{
uri_builder wUri(iAddress);
auto wAddress = wUri.to_uri().to_string();
gHttp = unique_ptr<MyServer>(new MyServer(wAddress));
gHttp->open().wait();
ucout << string_t(U("Listening for requests at: ")) << wAddress << endl;
}
void onShutdown()
{
gHttp->close().wait();
}
void main(int argc, wchar_t* argv[])
{
onInit(U("http://*:32123"));
cout << "Wait until connection occurs..." << endl;
getchar();
onShutdown();
}
sse.htm
<!DOCTYPE html>
<html lang="en-US">
<head>
<meta charset="utf-8">
</head>
<body>
<div id="result"></div>
</body>
</html>
<script>
if (typeof (EventSource) !== undefined)
{
document.getElementById("result").innerHTML += "SSE supported" + "<br>";
}
else
{
document.getElementById("result").innerHTML += "SSE NOT supported" + "<br>";
}
var source = new EventSource("http://localhost:32123/");
source.onopen = function ()
{
document.getElementById("result").innerHTML += "open" + "<br>";
};
source.onerror = function ()
{
document.getElementById("result").innerHTML += "error" + "<br>";
};
source.onmessage = function (event) {
document.getElementById("result").innerHTML += event.data + "<br>";
};
</script>
仅供参考。有一种基于brpc的解决方案:https://github.com/apache/brpc/pull/2375