void sock::perform_sock5_second_handshake() {

  std::uint16_t const port = 4561;
  std::uint8_t ipv4[4]{};
  std::vector<std::uint8_t> handshake_buffer{};

  std::cout << "Performing second handshake\n";
  if (sscanf("1.1.1.1", "%hhu.%hhu.%hhu.%hhu", &ipv4[0], &ipv4[1], &ipv4[2],
             &ipv4[3]) != 4) {
    throw std::runtime_error("Could not parse IPv4 address: 1.1.1.1");
  }

  handshake_buffer.clear();
  handshake_buffer.push_back(0x05); // version
  handshake_buffer.push_back(0x01); // TCP/IP
  handshake_buffer.push_back(0x00); // must be 0x00 always
  handshake_buffer.push_back(0x01); // IPv4

  // how do I specify the hostname here?
  handshake_buffer.push_back(ipv4[0]);
  handshake_buffer.push_back(ipv4[1]);
  handshake_buffer.push_back(ipv4[2]);
  handshake_buffer.push_back(ipv4[3]);

  // host to network short(htons)
  handshake_buffer.push_back(port >> 8);
  handshake_buffer.push_back(port & 0xff);

  ::send(socket_, reinterpret_cast<char const*>( handshake_buffer.data() ), handshake_buffer.size(), 0 );
}