{

public:

virtual ~Adapter() noexcept = default;

virtual System::native_socket_type get_handle() const noexcept = 0;

virtual ::gnutls_session_t get_tls_session() const noexcept = 0;

virtual Adapter *copy() const noexcept = 0;

long nonblock_recv(

std::vector<std::string::value_type> &buf,

const std::chrono::milliseconds &timeout

) const noexcept;

virtual long nonblock_recv(

void *buf,

const size_t length,

const std::chrono::milliseconds &timeout

) const noexcept = 0;

long nonblock_send(

const std::string &buf,

const std::chrono::milliseconds &timeout

) const noexcept;

virtual long nonblock_send(

const void *buf,

const size_t length,

const std::chrono::milliseconds &timeout

) const noexcept = 0;

virtual void close() noexcept = 0;

bool operator ==(const Adapter &obj) const noexcept;

bool operator !=(const Adapter &obj) const noexcept;