linjam/JuceLibraryCode/modules/juce_events/interprocess/juce_NetworkServiceDiscovery.h

/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2017 - ROLI Ltd.

   JUCE is an open source library subject to commercial or open-source
   licensing.

   The code included in this file is provided under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license. Permission
   To use, copy, modify, and/or distribute this software for any purpose with or
   without fee is hereby granted provided that the above copyright notice and
   this permission notice appear in all copies.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

//==============================================================================
/**
    Contains classes that implement a simple protocol for broadcasting the availability
    and location of a discoverable service on the local network, and for maintaining a
    list of known services.

    @tags{Events}
*/
struct NetworkServiceDiscovery
{
    /** An object which runs a thread to repeatedly broadcast the existence of a
        discoverable service.

        To use, simply create an instance of an Advertiser and it'll broadcast until
        you delete it.

        @tags{Events}
    */
    struct Advertiser  : private Thread
    {
        /** Creates and starts an Advertiser thread, broadcasting with the given properties.
            @param serviceTypeUID       A user-supplied string to define the type of service this represents
            @param serviceDescription   A description string that will appear in the Service::description field for clients
            @param broadcastPort        The port number on which to broadcast the service discovery packets
            @param connectionPort       The port number that will be sent to appear in the Service::port field
            @param minTimeBetweenBroadcasts   The interval to wait between sending broadcast messages
        */
        Advertiser (const String& serviceTypeUID,
                    const String& serviceDescription,
                    int broadcastPort,
                    int connectionPort,
                    RelativeTime minTimeBetweenBroadcasts = RelativeTime::seconds (1.5));

        /** Destructor */
        ~Advertiser() override;

    private:
        XmlElement message;
        const int broadcastPort;
        const RelativeTime minInterval;
        DatagramSocket socket { true };

        void run() override;
        void sendBroadcast();
    };

    //==============================================================================
    /**
        Contains information about a service that has been found on the network.

        @see AvailableServiceList, Advertiser

        @tags{Events}
    */
    struct Service
    {
        String instanceID;   /**< A UUID that identifies the particular instance of the Advertiser class.  */
        String description;  /**< The service description as sent by the Advertiser */
        IPAddress address;   /**< The IP address of the advertiser */
        int port;            /**< The port number of the advertiser */
        Time lastSeen;       /**< The time of the last ping received from the advertiser */
    };

    //==============================================================================
    /**
        Watches the network for broadcasts from Advertiser objects, and keeps a list of
        all the currently active instances.

        Just create an instance of AvailableServiceList and it will start listening - you
        can register a callback with its onChange member to find out when services
        appear/disappear, and you can call getServices() to find out the current list.

        @see Service, Advertiser

        @tags{Events}
    */
    struct AvailableServiceList  : private Thread,
                                   private AsyncUpdater
    {
        /** Creates an AvailableServiceList that will bind to the given port number and watch
            the network for Advertisers broadcasting the given service type.

            This will only detect broadcasts from an Advertiser object with a matching
            serviceTypeUID value, and where the broadcastPort matches.
        */
        AvailableServiceList (const String& serviceTypeUID, int broadcastPort);

        /** Destructor */
        ~AvailableServiceList() override;

        /** A lambda that can be set to receive a callback when the list changes */
        std::function<void()> onChange;

        /** Returns a list of the currently known services. */
        std::vector<Service> getServices() const;

    private:
        DatagramSocket socket { true };
        String serviceTypeUID;
        CriticalSection listLock;
        std::vector<Service> services;

        void run() override;
        void handleAsyncUpdate() override;
        void handleMessage (const XmlElement&);
        void handleMessage (const Service&);
        void removeTimedOutServices();

        JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (AvailableServiceList)
    };
};

} // namespace juce