signal(SIGINT, exit_handler);

uint16_t port = 37;

std::string time_host = "time.nist.gov"; //https://tf.nist.gov/tf-cgi/servers.cgi#

if (argc == 3) {

time_host = argv[1];

port = std::atol(argv[2]);

}

std::cout << "Connecting to " << time_host << " on port " << port << std::endl;

netlib::client client;

std::error_condition client_create_res =

client.connect(time_host, port, netlib::AddressFamily::IPv4,

netlib::AddressProtocol::UDP, 1000ms);

if (client_create_res) {

std::cerr << "Error connecting to host, error : " << client_create_res.message() << std::endl;

exit(EXIT_FAILURE);

}

//since time uses udp, we need to send some random udp datagram to server,

//since it has no way of knowing that we want the datetime

//(udp is connectionless)

//Interesting that the send payload can be lower than the 4 expected bytes -

//this could potentially be used in an udp reflection attack

std::vector<uint8_t> dummy_payload(4, 0);

auto send_res = client.send(dummy_payload, 1000ms);

if (send_res.second) {

std::cout << "Error sending byte in udp mode for triggering response: " <<

send_res.second.message() << std::endl;

exit(EXIT_FAILURE);

}

auto time_res = client.recv(1024, 1000ms);

if (time_res.second) {

std::cerr << "Failed to get UDP datagram. Error: " << time_res.second.message() << std::endl;

exit(EXIT_FAILURE);

}

if (time_res.first.size() != 4) {

std::cerr << "Did not recieve 32 bits - instead got " << time_res.first.size() << std::endl;

exit(EXIT_FAILURE);

}

uint32_t time_result = (time_res.first[0] << 24) |

(time_res.first[1] << 16) |

(time_res.first[2] << 8) |

(time_res.first[3]);

std::cout << "Value from server: " << time_result << std::endl;

//print out actual time

std::time_t temp = time_result - 2208988800;

std::cout << std::put_time(std::gmtime(&temp), "Formatted: %Y-%m-%d %I:%M:%S %p") << std::endl;

}