在网络套接字计时器滴答后增加asio短读错误

Question

我正在尝试使用 websocketpp 连接到安全的 websocket，但在计时器的第二次滴答声后出现这个奇怪的错误：

[2019-12-05 10:48:55] [info] asio async_read_at_least error: asio.ssl:335544539 (short read)
[2019-12-05 10:48:55] [error] handle_read_frame error: websocketpp.transport:11 (Generic TLS related error)
[2019-12-05 10:48:55] [info] asio async_write error: asio.ssl:336396495 (protocol is shutdown)
[2019-12-05 10:48:55] [fatal] handle_write_frame error: websocketpp.transport:2 (Underlying Transport Error)
[2019-12-05 10:48:55] [info] asio async_shutdown error: asio.ssl:335544539 (short read)
close handler: Underlying Transport Error
[2019-12-05 10:48:55] [disconnect] Disconnect close local:[1006,Underlying Transport Error] remote:[1000]

我的代码是：

#define _WEBSOCKETPP_CPP11_STL_
#   ifdef _WIN32
#       pragma warning(disable: 4503)
#       pragma warning(disable: 4996)
#   endif
#   include <websocketpp/config/asio_client.hpp>
#   include <websocketpp/client.hpp>
#   include <websocketpp/frame.hpp>
#undef _WEBSOCKETPP_CPP11_STL_
#include <iostream>
using WSClient = websocketpp::client<websocketpp::config::asio_tls_client>;
int main()
{
WSClient client;
client.init_asio();
client.set_tls_init_handler([](auto)
{
auto result = websocketpp::lib::make_shared<boost::asio::ssl::context>(boost::asio::ssl::context::sslv23_client);
result->set_verify_mode(boost::asio::ssl::verify_none);
return result;
});
client.set_open_handler([&client](auto hdl)
{
client.set_timer(40000, [hdl, &client](auto)
{
if (auto con = client.get_con_from_hdl(hdl)) {
con->send(std::string(R"({"op":1,"d":1})"), websocketpp::frame::opcode::text);
}
});
});
client.set_close_handler([&client](auto hdl)
{
auto con = client.get_con_from_hdl(hdl);
std::cout << "close handler: " << con->get_ec().message() << std::endl;
});
client.set_fail_handler([&client](auto hdl)
{
auto con = client.get_con_from_hdl(hdl);
std::cout << "fail handler: " << con->get_ec().message() << std::endl;
});
websocketpp::lib::error_code ec;
const auto websocketUrl = "wss://gateway.discord.gg/?encoding=json&v=6";
auto con = client.get_connection(websocketUrl, ec);
if (ec) {
std::cout << "Could not create WebSocket connection because " << ec.message() << std::endl;
return 0;
}
client.connect(con);
client.run();
}

令人惊讶的是，如果我使用 NodeJS 做同样的事情，它可以使用以下方法正常工作：

const WebSocket = require('ws');
let websocketUrl = 'wss://gateway.discord.gg/?encoding=json&v=6'
const ws = new WebSocket(websocketUrl);
ws.on('open', function() {
setInterval(() => {
console.log('ping');
ws.send('{"op":1,"d":1}');
}, 40000);
});
ws.on('error', function(e, v){
console.log('error', e, v);
});
ws.on('unexpected-response', function(e, t, v){
console.log('unexpected-response', e, t);
});
ws.on('close', function() {
console.log('connection closed');
});

我在C++版本中做错了什么？

环境： Windows 10， MSVC 14， Websocketpp 0.8.1， Boost 1.69

Answer 1

根据文档 [1]，客户端必须发送 ping(手册称它们为心跳(：

心跳：

用于维护活动网关连接。必须在收到操作码 10 Hello 有效负载后每 heartbeat_interval 毫秒发送一次。内部 d 键是客户端接收的最后一个序列号 (s(。如果尚未收到，请发送空值。

您正在使用 WSClient：：set_timer(((在 set_open 方法中(在 C++ 实现中发送 ping 消息。但是，WSClient：：set_timer(( 只调用一次 ping 函数(您可以使用 printf 进行检查或阅读该方法的文档(。因此，您只发送一条 ping 消息。因此，您的连接将在一段时间后从服务器终止。

相反，你在 NodeJS 实现中使用 "setIntervall((" 来设置一个周期性的计时器。因此，会定期调用此计时器，并且服务器会定期接收您的ping消息。

我做了以下操作来修复您的C++代码[答案末尾复制粘贴的完整代码]：

1.( 添加一个处理程序来读取传入消息以进行调试：

client.set_message_handler([&client](auto hdl, auto msg_ptr)
{
std::string message = msg_ptr->get_payload();
std::cout << "received message: " << message << std::endl;
});

2.( 以非阻塞方式启动 websocket

：

auto run_thread = std::thread{[&client](){client.run();}}; 
while(! client_is_open) { //this variable is defined elsewhere, see full code
sleep(1); //TODO: use an mutex instead
}

3.( 执行 ping：

int heartbeat_interval = 41250; //in ms: TODO extract from message
while(true) {
std::this_thread::sleep_for(std::chrono::milliseconds(heartbeat_interval));
client.send(con, "{"op":1, "d":null}", websocketpp::frame::opcode::text);
}

请注意以下事项：

1. 您必须从第一条消息中提取 ping 间隔。(我没有(
ping
2. 消息应发送最后一个 ping 的序列号(请参阅文档(。我没有，它仍然有效，但不要指望这一点。
3. client.run(( 是一个阻塞调用，有一些问题。

你可以在下面找到我的代码

[1] https://github.com/discordapp/discord-api-docs/blob/master/docs/topics/Gateway.md#DOCS_TOPICS_GATEWAY/heartbeat

#define _WEBSOCKETPP_CPP11_STL_
#   ifdef _WIN32
#       pragma warning(disable: 4503)
#       pragma warning(disable: 4996)
#   endif
#   define _WEBSOCKETPP_CPP11_STL_
#   include <websocketpp/config/asio_client.hpp>
#   include <websocketpp/client.hpp>
#   include <websocketpp/frame.hpp>
#undef _WEBSOCKETPP_CPP11_STL_
#include <iostream>
using WSClient = websocketpp::client<websocketpp::config::asio_tls_client>;;
int main() { WSClient client;
client.init_asio();
bool client_is_open = false;
client.set_tls_init_handler([](auto)
{
auto result = websocketpp::lib::make_shared<boost::asio::ssl::context>(boost::asio::ssl::context::sslv23_client);
result->set_verify_mode(boost::asio::ssl::verify_none);
return result;
});
client.set_open_handler([&client,&client_is_open](auto hdl)
{
client_is_open=true;
});
client.set_close_handler([&client](auto hdl)
{
auto con = client.get_con_from_hdl(hdl);
std::cout << "close handler: " << con->get_ec().message() << std::endl;
});
client.set_fail_handler([&client](auto hdl)
{
auto con = client.get_con_from_hdl(hdl);
std::cout << "fail handler: " << con->get_ec().message() << std::endl;
});
client.set_message_handler([&client](auto hdl, auto msg_ptr)
{
std::string message = msg_ptr->get_payload();
std::cout << "received message: " << message << std::endl;
});
websocketpp::lib::error_code ec;
const auto websocketUrl = "wss://gateway.discord.gg/?encoding=json&v=6";
auto con = client.get_connection(websocketUrl, ec);
if (ec) {
std::cout << "Could not create WebSocket connection because " << ec.message() << std::endl;
return 0;
}
client.connect(con);
auto run_thread = std::thread{[&client](){client.run();}};
while(! client_is_open) {
sleep(1); //TODO: use an mutex instead
}
int heartbeat_interval = 41250; //in ms: TODO extract from message
while(true) {
std::this_thread::sleep_for(std::chrono::milliseconds(heartbeat_interval));
client.send(con, "{"op":1, "d":null}", websocketpp::frame::opcode::text);
} 
run_thread.join();
}