c++ - websocket计时器滴答后 boost asio短读错误

Question

我正在尝试使用websocketpp连接到安全的websocket，但是在计时器的第二个滴答声后出现此奇怪的错误:

[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进行相同的操作，则可以使用以下命令正常工作:

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');
});

在C++版本中我在做什么错？

信封: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):

Heartbeat:

Used to maintain an active gateway connection. Must be sent every heartbeat_interval milliseconds after the Opcode 10 Hello payload is received. The inner d key is the last sequence number—s—received by the client. If you have not yet received one, send null.

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()仅调用一次ping函数(您可以使用printf进行检查或阅读该方法的文档)。因此，您只发送一个ping消息。因此，从服务器上断开连接后，您的连接将被终止。
相反，您在NodeJS实现中使用“setIntervall()”来设置定期计时器。因此，将定期调用此计时器，并且服务器会定期接收您的ping消息。
我做了以下工作来修复您的C++代码[答案结尾处用于复制粘贴的完整代码]:
1.)添加处理程序以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操作:

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:

您必须从第一条消息中提取ping间隔。 (我没有)

ping消息应发送上次ping的序列号(请参阅相关文档)。我没有，它仍然有效，但是不要指望它。

client.run()是一个阻止调用，对此存在一些问题。

您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();

}