    // Copyright (C) 2006  Davis E. King (davis@dlib.net)
    // License: Boost Software License   See LICENSE.txt for the full license.
    #undef DLIB_SOCKETS_EXTENSIONs_ABSTRACT_
    #ifdef DLIB_SOCKETS_EXTENSIONs_ABSTRACT_

    #include <string>
    #include "sockets_kernel_abstract.h"
    #include "../smart_pointers.h"
    #include "../error.h"

    namespace dlib
    {

    // ----------------------------------------------------------------------------------------

        class invalid_network_address : public dlib::error
        {
            /*!
                WHAT THIS OBJECT REPRESENTS
                    This is the exception thrown by network_address's constructor if the
                    input is invalid.
            !*/
        };

    // ----------------------------------------------------------------------------------------

        struct network_address
        {
            /*!
                WHAT THIS OBJECT REPRESENTS
                    This object is simply a container for two things:
                        - A host machine address which is either an IP address or DNS name
                          for a machine.
                        - A port number.

                    Together, these things define a machine and port on that machine.
            !*/

            network_address(
            );
            /*!
                ensures
                    - host_address == ""
                    - #port == 0
            !*/

            network_address(
                const std::string& full_address
            );
            /*!
                ensures
                    - interprets full_address as a network address of the form:
                        host_address:port
                      and assigns each part into #host_address and #port.  For example,
                      network_address("localhost:80") would result in a network_address
                      object where host_address was "localhost" and port was 80.
                throws
                    - invalid_network_address
                        This exception is thrown if the full_address string can't be
                        interpreted as a valid network address.
            !*/

            network_address (
                const char* full_address
            );
            /*!
                requires
                    - full_address == a valid pointer to a null terminated string
                ensures
                    - Invoking this constructor is equivalent to performing
                      network_address(std::string(full_address))
            !*/

            network_address(
                const std::string& host_address_,
                const unsigned short port_
            );
            /*!
                ensures
                    - #host_address == host_address_
                    - #port == port_
            !*/

            std::string host_address;
            unsigned short port;
        };

    // ----------------------------------------------------------------------------------------

        inline bool operator < (
            const network_address& a,
            const network_address& b
        );
        /*!
            ensures
                - provides a total ordering over network_address objects so you can use them in
                  the standard associative containers.  The ordering is defined such that if
                  you sorted network addresses they would sort first on the host_address string
                  and then, for network_address objects with equal host_address, they would
                  sort on the port number
        !*/

        inline bool operator== (
            const network_address& a,
            const network_address& b
        );
        /*!
            ensures
                - returns true if a and b contain exactly the same address and false otherwise.
                  That is, the following must be true for this function to return true:
                    - a.host_address == b.host_address
                    - a.port == b.port
                  Note that this means that two addresses which are logically equivalent but
                  written differently will not compare equal.  For example, suppose example.com
                  has the IP address 10.1.1.1.  Then network_address("10.1.1.1:80") and
                  network_address("example.com:80") really refer to the same network resource
                  but will nevertheless not compare equal since.
        !*/

        inline bool operator != (
            const network_address& a,
            const network_address& b
        );
        /*!
            ensures
                - returns !(a == b)
        !*/

    // ----------------------------------------------------------------------------------------

        void serialize(
            const network_address& item,
            std::ostream& out
        );
        /*!
            ensures
                - provides serialization support
        !*/

        void deserialize(
            network_address& item,
            std::istream& in
        );
        /*!
            ensures
                - provides deserialization support
        !*/

        std::ostream& operator<< (
            std::ostream& out,
            const network_address& item
        );
        /*!
            ensures
                - writes the given network_address to the output stream.  The format is the
                  host_address, then a colon, then the port number.  So for example:
                    cout << network_address("localhost", 80);
                  would print:
                    localhost:80
                - returns #out
        !*/

        std::istream& operator>> (
            std::istream& in,
            network_address& item
        );
        /*!
            ensures
                - reads a network_address from the given input stream.  The expected format is
                  the same as the one used to print them by the above operator<<() routine.
                - returns #in
                - if (there is an error reading the network_address) then
                    - #in.good() == false
        !*/

    // ----------------------------------------------------------------------------------------

        connection* connect (
            const std::string& host_or_ip,
            unsigned short port
        );
        /*!
            ensures
                - returns a connection object that is connected to the given host at the
                  given port
            throws
                - dlib::socket_error
                    This exception is thrown if there is some problem that prevents us from
                    creating the connection
                - std::bad_alloc
        !*/

    // ----------------------------------------------------------------------------------------

        connection* connect (
            const network_address& addr
        );
        /*!
            ensures
                - returns connect(addr.host_address, addr_port);
        !*/

    // ----------------------------------------------------------------------------------------

        connection* connect (
            const std::string& host_or_ip,
            unsigned short port,
            unsigned long timeout
        );
        /*!
            ensures
                - returns a connection object that is connected to the given host at the
                  given port.
                - blocks for at most timeout milliseconds
            throws
                - dlib::socket_error
                    This exception is thrown if there is some problem that prevents us from
                    creating the connection or if timeout milliseconds elapses before the
                    connect is successful.
                - std::bad_alloc
        !*/

    // ----------------------------------------------------------------------------------------

        bool is_ip_address (
            std::string ip
        );
        /*!
            ensures
                - if (ip is a valid ip address) then
                    - returns true
                - else
                    - returns false
        !*/

    // ----------------------------------------------------------------------------------------

        void close_gracefully (
            connection* con,
            unsigned long timeout = 500
        );
        /*!
            requires
                - con == a valid pointer to a connection object or 0
            ensures
                - This function does nothing if con == 0, otherwise it performs the following:
                    - performs a graceful close of the given connection and if it takes longer
                      than timeout milliseconds to complete then forces the connection closed.
                        - Specifically, a graceful close means that the outgoing part of con is
                          closed (a FIN is sent) and then we wait for the other end to to close
                          their end of the connection.  This way any data still on its way to
                          the other end of the connection will be received properly.
                    - This function will block until the graceful close is completed or we
                      timeout.
                    - calls "delete con;".  Thus con is no longer a valid pointer after this
                      function has finished.
            throws
                - std::bad_alloc or dlib::thread_error
                    If either of these exceptions are thrown con will still be closed via
                    "delete con;"
        !*/

    // ----------------------------------------------------------------------------------------

        void close_gracefully (
            scoped_ptr<connection>& con,
            unsigned long timeout = 500
        );
        /*!
            requires
                - con == a valid pointer to a connection object or con.get() == 0
            ensures
                - This function does nothing if con.get() == 0, otherwise it performs the
                  following:
                    - performs a graceful close of the given connection and if it takes longer
                      than timeout milliseconds to complete then forces the connection closed.
                        - Specifically, a graceful close means that the outgoing part of con is
                          closed (a FIN is sent) and then we wait for the other end to to close
                          their end of the connection.  This way any data still on its way to
                          the other end of the connection will be received properly.
                    - This function will block until the graceful close is completed or we
                      timeout.
                    - #con.get() == 0.  Thus con is no longer a valid pointer after this
                      function has finished.
            throws
                - std::bad_alloc or dlib::thread_error
                    If either of these exceptions are thrown con will still be closed and
                    deleted (i.e. #con.get() == 0).
        !*/

    // ----------------------------------------------------------------------------------------

    }

    #endif // DLIB_SOCKETS_EXTENSIONs_ABSTRACT_