ProtocolInstance Class

public abstract class ProtocolInstance : ProtocolSocket

using System.Threading.Tasks;
using Demo3D.Net;

namespace Examples.Net.ExampleProtocol {
    /// <summary>
    /// An interface that describes the services (the IO methods) that your protocol supports.
    /// Typically a protocol would implement one of the standard services (such as <see cref="IPacketIOService"/>).
    /// </summary>
    interface IExampleService {
        // Put whatever methods users of your protocol would expect in here.
    }

    /// <summary>
    /// An instance of a protocol.  Must inherit from <see cref="ProtocolInstance"/>, and should
    /// support a set of services.  The simplest way to support services is to implement the
    /// services interface (<see cref="IExampleService"/>) and to advertise those services in the
    /// <see cref="ExampleProtocol.NewInstance(ProtocolHead, ProtocolAddress)"/> constructor.
    /// </summary>
    /// <remarks>
    /// See <see cref="TCPExample.Client.TcpClientProtocol.TcpClientConnection"/> for an
    /// example implementing the TCP protocol.
    /// </remarks>
    class ExampleProtocolInstance : ProtocolInstance, IExampleService {
        public ExampleProtocolInstance(Protocol protocol, ProtocolHead head, ProtocolAddress address) : base(protocol, head, address, false, null) { }

        /// <summary>
        /// Initializes the socket.
        /// </summary>
        /// <param name="sync">If true, the Task returned must be guaranteed to be complete.</param>
        protected override Task InitializeAsync(bool sync) {
            // Any initialization code goes here.
            return Task.CompletedTask;
        }

        /// <summary>
        /// Indicates whether the instance is still running.
        /// </summary>
        protected override bool InternalRunning => base.InternalRunning;  // Return true if the connection is established

        /// <summary>
        /// Opens or reopens the instance.
        /// </summary>
        /// <param name="sync">If true, the Task returned must be guaranteed to be complete.</param>
        /// <param name="flags">Additional flags.</param>
        protected override Task InternalOpenAsync(bool sync, Flags flags) {
            // Open your connection here.
            return Task.CompletedTask;
        }

        /// <summary>
        /// Forcibly shuts down the underlying protocol, causing all other users to throw an error.
        /// </summary>
        protected override void InternalShutdown() {
            // Forcibly shut the connection down.
        }

        /// <summary>
        /// Performs a controlled close.
        /// </summary>
        protected override void InternalClose() {
            // Called to close the connection.
            InternalShutdown();
        }

        // Implement any IExampleService methods here.
    }

    /// <summary>
    /// A protocol inherits from <see cref="Protocol"/>.
    /// </summary>
    /// See <see cref="TCPExample.Client.TcpClientProtocol"/> for an example implementing the TCP protocol,
    /// or <see cref="TCPExample.Server.TcpServerProtocol"/> for an example implementing a TCP server.
    /// </remarks>
    class ExampleProtocol : Protocol {
        /// <summary>
        /// Constructs a new protocol.
        /// You need to give your protocol a name, and advertise which services it supports.
        /// </summary>
        public ExampleProtocol() : base("Example", typeof(IExampleService)) { }

        /// <summary>
        /// Create a new server/client protocol instance.
        /// At the minimum, you need to implement this method to return a new instance of your protocol.
        /// </summary>
        /// <param name="head">The socket head which is a required parameter to the ProtocolInstance constructor.</param>
        /// <param name="protocolAddress">The protocol address.</param>
        /// <returns>A new ProtocolInstance.</returns>
        protected override ProtocolInstance NewInstance(ProtocolHead head, ProtocolAddress protocolAddress) {
            return new ExampleProtocolInstance(this, head, protocolAddress);
        }

        /// <summary>
        /// Registers the protocol with Demo3D.Net.
        /// You need to call this method somewhere in your code in order to register this protocol with Demo3D.Net.
        /// </summary>
        public static void Register() {
            Registry.Register(new ExampleProtocol());
        }
    }
}

using System.ComponentModel;
using System.IO;
using System.Net.Sockets;
using System.Threading.Tasks;
using Demo3D.IO;
using Demo3D.Net;

using TcpClient = System.Net.Sockets.TcpClient;

namespace Examples.Net.TCPExample.Client {
    /// <summary>
    /// TCP address editor.
    /// </summary>
    public class TcpAddressEditor : ProtocolAddressPropertyBagEditor {
        string host;
        int    port;

        /// <summary>
        /// The server host.
        /// </summary>
        [Description("The server host.")]
        [Category("Connection")]
        public string Host {
            get { return host; }
            set {
                if (host != value) {
                    host = value;
                    NotifyPropertyChanged();
                }
            }
        }

        /// <summary>
        /// The server port.
        /// </summary>
        [Description("The server port.")]
        [Category("Connection")]
        public int Port {
            get { return port; }
            set {
                if (port != value) {
                    port = value;
                    NotifyPropertyChanged();
                }
            }
        }

        /// <summary>
        /// Returns a ProtocolAddress that represents the configuration defined by this object.
        /// </summary>
        /// <returns>The protocol address according to the current setting of the editor properties.</returns>
        public override ProtocolAddress GetAddress() {
            return new ProtocolAddressBuilder("tcp", host, port).Address;
        }

        /// <summary>
        /// Sets this configuration object properties from the ProtocolAddress given.
        /// </summary>
        /// <param name="address">The current address.</param>
        public override void SetAddress(ProtocolAddress address) {
            host = address.Host;
            port = address.Port;
        }

        /// <summary>
        /// Returns the next property that needs to be edited to complete the address.
        /// </summary>
        /// <returns>The name of the property, or null.</returns>
        public override string NextProperty() {
            if (string.IsNullOrWhiteSpace(this.Host)) return nameof(this.Host);
            if (this.Port <= 0)                       return nameof(this.Port);
            return null;
        }
    }

    [ProtocolAddressEditor(Editor = typeof(TcpAddressEditor))]
    public sealed class TcpClientProtocol : Protocol {
        class TcpClientConnection : ProtocolInstance, IByteStreamService {
            TcpClient     tcpClient;
            NetworkStream stream;

            internal TcpClientConnection(Protocol protocol, ProtocolHead head, ProtocolAddress peerAddress)
                : base(protocol, head, peerAddress, true, null) {
            }

            protected override bool InternalRunning {
                get { return tcpClient != null && tcpClient.Connected; }
            }

            protected override async Task InternalOpenAsync(bool sync, Flags flags) {
                string host = this.Address.Host;
                int    port = this.Address.IsDefaultPort ? 0 : this.Address.Port;

                if (!this.Address.HasHost || port <= 0) {
                    throw Exceptions.ProtocolError("Host or port not configured", this);
                }

                tcpClient = new TcpClient();

                if (sync) tcpClient.Connect(host, port);
                else      await tcpClient.ConnectAsync(host, port).ConfigureAwait(false);

                stream = tcpClient.GetStream();
            }

            protected override void InternalShutdown() {
                try { tcpClient?.Client?.Shutdown(SocketShutdown.Both); }
                catch { }
            }

            protected override void InternalClose() {
                if (tcpClient == null) return;

                InternalShutdown();

                try { tcpClient?.Client?.Close(); }
                catch { }

                try { tcpClient?.Close(); }
                catch { }

                stream    = null;
                tcpClient = null;
            }

            bool   IByteStreamService.DataAvailable { get { return stream.DataAvailable; } }
            Stream IByteStreamService.Stream        { get { return stream;               } }
        }

        TcpClientProtocol() : base("TCP", typeof(IByteStreamService)) { }

        public static void Register() {
            Registry.Register(new TcpClientProtocol());
        }

        protected override ProtocolInstance NewInstance(ProtocolHead head, ProtocolAddress protocolAddress) {
             return new TcpClientConnection(this, head, protocolAddress);
        }
    }
}

using System;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Threading.Tasks;
using Demo3D.IO;
using Demo3D.Net;

using TcpClient = System.Net.Sockets.TcpClient;

namespace Examples.Net.TCPExample.Server {
    public sealed class TcpServerProtocol : Protocol {
        class TcpServerConnection : ProtocolInstance, IByteStreamService {
            TcpClient     tcpClient;
            NetworkStream stream;

            internal TcpServerConnection(TcpClient tcpClient, Protocol protocol, ProtocolHead head, ProtocolAddress peerAddress)
                : base(protocol, head, peerAddress, true, null) {
                this.tcpClient = tcpClient;
                stream         = tcpClient.GetStream();
            }

            protected override bool InternalRunning {
                get { return tcpClient != null && tcpClient.Connected; }
            }

            protected override Task InternalOpenAsync(bool sync, Flags flags) {
                throw new Exception("Cannot reconnect");
            }

            protected override void InternalShutdown() {
                try { tcpClient?.Client?.Shutdown(SocketShutdown.Both); }
                catch { }
            }

            protected override void InternalClose() {
                if (tcpClient == null) return;

                InternalShutdown();

                try { tcpClient?.Client?.Close(); }
                catch { }

                try { tcpClient?.Close(); }
                catch { }

                stream    = null;
                tcpClient = null;
            }

            bool   IByteStreamService.DataAvailable { get { return stream.DataAvailable; } }
            Stream IByteStreamService.Stream        { get { return stream;               } }
        }

        sealed class TcpServer : ProtocolInstance, IProtocolServerService {
            TcpListener listener;

            internal TcpServer(Protocol protocol, ProtocolHead head, ProtocolAddress protocolAddress)
                : base(protocol, head, protocolAddress, false, null) {
            }

            protected override bool InternalRunning { get { return listener != null; } }

            protected override async Task InternalOpenAsync(bool sync, Flags flags) {
                int       port = this.Address.IsDefaultPort ? 0 : this.Address.Port;
                IPAddress ipAddress;

                switch (this.Address.Host) {
                    case "":
                    case ProtocolAddress.AnyHost:
                        ipAddress = IPAddress.Any;
                        break;

                    default:
                        ipAddress = await IPv4.HostToIPAddressAsync(sync, this.Address.Host).ConfigureAwait(false);
                        break;
                }

                listener = new TcpListener(ipAddress, port);
                listener.Start();
            }

            protected override void InternalShutdown() {
                try { listener?.Server.Close(); }
                catch { }
            }

            protected override void InternalClose() {
                try { listener?.Stop(); }
                catch { }
                listener = null;
            }

            async Task<ProtocolInstance> IProtocolServerService.InternalAcceptAsync(bool sync, ProtocolHead head, ProtocolInstance downStreamConnection) {
                TcpClient client;

                if (sync) client = listener.AcceptTcpClient();
                else      client = await listener.AcceptTcpClientAsync().ConfigureAwait(false);

                var endPoint = (IPEndPoint)client.Client.RemoteEndPoint;
                var address  = new ProtocolAddressBuilder("tcp", endPoint.Address.ToString(), endPoint.Port).Address;

                return new TcpServerConnection(client, this.Protocol, head, address);
            }
        }

        TcpServerProtocol() : base("TCP", typeof(IProtocolServerService), typeof(IByteStreamService)) { }

        public static void Register() {
            Registry.Register(new TcpServerProtocol());
        }

        protected override ProtocolInstance NewInstance(ProtocolHead head, ProtocolAddress protocolAddress) {
            return new TcpServer(this, head, protocolAddress);
        }
    }
}