How to handle ping request on client (boost::beast::websocket) - c++

Question

Imagine that you have some websocket client, that downloading some data in loop like this:
#include <boost/asio.hpp>
#include <boost/beast.hpp>
#include "nlohmann/json.hpp"
namespace beast = boost::beast;
namespace websocket = beast::websocket;
using tcp = boost::asio::ip::tcp;
class Client {
public:
Client(boost::asio::io_context &ctx) : ws_{ctx}, ctx_{ctx} {
ws_.set_option(websocket::stream_base::timeout::suggested(boost::beast::role_type::client));
#define HOST "127.0.0.1"
#define PORT "8000"
boost::asio::connect(ws_.next_layer(), tcp::resolver{ctx_}.resolve(HOST, PORT));
ws_.handshake(HOST ":" PORT, "/api/v1/music");
#undef HOST
#undef PORT
}
~Client() {
if (ws_.is_open()) {
ws_.close(websocket::normal);
}
}
nlohmann::json NextPacket(std::size_t offset) {
nlohmann::json request;
request["offset"] = offset;
ws_.write(boost::asio::buffer(request.dump()));
beast::flat_buffer buffer;
ws_.read(buffer);
return nlohmann::json::parse(std::string_view{reinterpret_cast<const char *>(buffer.data().data()), buffer.size()});
}
private:
boost::beast::websocket::stream<boost::asio::ip::tcp::socket> ws_;
boost::asio::io_context &ctx_;
};
// ... some function
int main() {
boost::asio::io_context context;
boost::asio::executor_work_guard<boost::asio::io_context::executor_type> guard{context.get_executor()};
std::thread{[&context]() { context.run(); }}.detach();
static constexpr std::size_t kSomeVeryBigConstant{1'000'000'000};
Client client{context};
std::size_t offset{};
while (offset < kSomeVeryBigConstant) {
offset += client.NextPacket(offset)["offset"].get<std::size_t>();
// UPDATE:
userDefinedLongPauseHere();
}
}
On the server side we have ping requests with some frequency. Were should I handle ping requests? As I understand it, control_callback controls calls to ping, pong and close functions, not requests. With the read or read_async functions, I also cannot catch the ping request.

Answer 1

Beast responds to pings with pongs automatically, as described here: https://github.com/boostorg/beast/issues/899#issuecomment-346333014
Whenever you call read(), it can process a ping and send a pong without you knowing about that.