boost::asio - can't set keepalive value

Question

I have copied the chat-example from the boost examples.

server code: https://www.boost.org/doc/libs/1_53_0/doc/html/boost_asio/example/chat/chat_server.cpp
chat_message.hpp: https://www.boost.org/doc/libs/1_53_0/doc/html/boost_asio/example/chat/chat_message.hpp
client code: https://www.boost.org/doc/libs/1_53_0/doc/html/boost_asio/example/chat/chat_client.cpp

In chat_server.cpp, I have added a cout in chat_room::leave to get notified when a client leaves. In chat_server, I tried to configure TCP keepalive according to this SO answer:

// additional includes that I have added
#include <winsock2.h>
#include <ws2tcpip.h>
#include <ws2spi.h>
#include <mstcpip.h>
#include <windows.h>

// ----
class chat_server {
public:
    chat_server(boost::asio::io_service& io_service,
                const tcp::endpoint& endpoint)
        : acceptor_(io_service, endpoint),
        socket_(io_service) {
        do_accept();
    }

private:
    void do_accept() {
        acceptor_.async_accept(socket_,
                               [this](boost::system::error_code ec) {
                                   if(!ec) {
                                       unsigned long val = 1;
                                       int res = setsockopt(socket_.native_handle(), SOL_SOCKET, SO_KEEPALIVE, (char*) &val, sizeof val);
                                       if(res) std::cout << "Can't set sockopt!" << std::endl;

                                       tcp_keepalive alive;
                                       alive.onoff = TRUE;
                                       alive.keepalivetime = 1000;
                                       alive.keepaliveinterval = 1000;
                                       DWORD bytes_ret = 0;
                                       res = WSAIoctl(socket_.native_handle(), SIO_KEEPALIVE_VALS, &alive, sizeof(alive), NULL, 0,
                                                      &bytes_ret, NULL, NULL);
                                       if(res) std::cout << "Can't set TCP keepalive!" << std::endl;

                                       std::make_shared<chat_session>(std::move(socket_), room_)->start();
                                   }

                                   do_accept();
                               });
    }

    tcp::acceptor acceptor_;
    tcp::socket socket_;
    chat_room room_;
};

My test setup is to run the server on my local machine. The client runs on a "VMware Workstation 15 Player"-virtual machine, where NAT is used as network adapter. When I connect to the server and uncheck the "Connected"-checkbox in Virtual Machine Settings (should be the same as unplugging the network cable), I would expect to see the output of chat_room::leave in the console, but it seems, that the server even after a few minutes thinks that the client is still connected.

How can I configure the TCP keepalive appropriately? (I would prefer a cross-platform solution which works on Linux too, but if it works on windows, it's better than nothing)

Edit: I have monitored the sent data with Wireshark and found out that no keep-alive packets were sent. What could cause this?

boost::asio - can't set keepalive value

0 Answers0