用c#开发安卓程序 (xamarin.android)系列之二 容易的聊天程序

using System;
using Android.App;
using Android.Content;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
using System.Net;
using System.Collections.Generic;
using System.IO;

namespace ExamplesChat.Android
{
    [Activity(Label = "ExamplesChat.Android", MainLauncher = true, Icon = "@drawable/icon")]
    public class Activity1 : Activity
    {
        #region Private Fields
        /// <summary>
        /// 一个聊天程序的实例
        /// </summary>
        ChatAppAndroid chatApplication;

        /// <summary>
        /// 用于显示聊天消息
        /// </summary>
        TextView chatHistory;

        /// <summary>
        /// 发送消息按钮
        /// </summary>
        Button sendButton;
        
        /// <summary>
        /// 消息输入框
        /// </summary>
        AutoCompleteTextView input;

        /// <summary>
        /// The texbox containing the master ip address (server)
        /// </summary>
        AutoCompleteTextView ipTextBox;

        /// <summary>
        /// The texbox containing the master port number (server)
        /// </summary>
        AutoCompleteTextView portTextBox;

        /// <summary>
        /// The spinner (drop down) menu for selecting the connection type to use
        /// </summary>
        Spinner connectionTypeSelector;

        /// <summary>
        /// The checkbox which can be used to enable local server mode
        /// </summary>
        CheckBox enableLocalServerCheckBox;
        #endregion

        /// <summary>
        /// Method runs after the application has been launched
        /// </summary>
        /// <param name="bundle"></param>
        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);

            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.Main);

            //Get references to user interface controls
            connectionTypeSelector = FindViewById<Spinner>(Resource.Id.connectionTypeSpinner);
            chatHistory = FindViewById<TextView>(Resource.Id.mainText);
            input = FindViewById<AutoCompleteTextView>(Resource.Id.messageTextInput);
            ipTextBox = FindViewById<AutoCompleteTextView>(Resource.Id.ipTextInput);
            portTextBox = FindViewById<AutoCompleteTextView>(Resource.Id.portTextInput);
            sendButton = FindViewById<Button>(Resource.Id.sendButton);
            enableLocalServerCheckBox = FindViewById<CheckBox>(Resource.Id.enableLocalServer);

            //Set the connection type selection drop down options
            ArrayAdapter adapter = ArrayAdapter.CreateFromResource(this, Resource.Array.ConnectionTypes, global::Android.Resource.Layout.SimpleSpinnerItem);
            adapter.SetDropDownViewResource(global::Android.Resource.Layout.SimpleSpinnerDropDownItem);
            connectionTypeSelector.Adapter = adapter;

            //Append the method 'connectionType_Selected' to the connection type selected event
            connectionTypeSelector.ItemSelected += connectionType_Selected;

            //Append the method 'sendButton_Click' to the button click event
            sendButton.Click += sendButton_Click;

            //Append the method 'enableLocalServerCheckBox_CheckedChange' when the enable
            //local server checkbox state is changed
            enableLocalServerCheckBox.CheckedChange += enableLocalServerCheckBox_CheckedChange;

            //Initialise the chat application
            chatApplication = new ChatAppAndroid(this, chatHistory, input);

            //Print the usage instructions
            chatApplication.PrintUsageInstructions();

            //Initialise NetworkComms.Net but without a local server
            chatApplication.RefreshNetworkCommsConfiguration();

            //Uncomment this line to enable logging
            //EnableLogging();
        }

        /// <summary>
        /// Enable NetworkComms.Net logging. Usefull for debugging.
        /// </summary>
        void EnableLogging()
        {
            //We will create the log file in the root external storage directory
            string sdCardDir = global::Android.OS.Environment.ExternalStorageDirectory.AbsolutePath;
            string logFileName = Path.Combine(sdCardDir, "NetworkCommsLog.txt");

            chatApplication.AppendLineToChatHistory(System.Environment.NewLine + "Logging enabled to " + logFileName);

            NetworkCommsDotNet.NetworkComms.EnableLogging(logFileName);
        }

        #region Event Handlers
        /// <summary>
        /// Event triggered when the enable local server checkbox is changed
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void enableLocalServerCheckBox_CheckedChange(object sender, CompoundButton.CheckedChangeEventArgs e)
        {
            //Update the local server enabled state and then refresh the network configuration
            chatApplication.LocalServerEnabled = enableLocalServerCheckBox.Checked;
            chatApplication.RefreshNetworkCommsConfiguration();
        }

        /// <summary>
        /// Event triggered when the send button is clicked
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void sendButton_Click(object sender, EventArgs e)
        {
            //Parse the ip address box
            if (ipTextBox.Text != "")
            {
                IPAddress newMasterIPAddress;
                if (IPAddress.TryParse(ipTextBox.Text, out newMasterIPAddress))
                    //If the parse was succesfull we can update the chat application
                    chatApplication.ServerIPAddress = newMasterIPAddress.ToString();
                else
                    //If the parse failed set the ipTextBox back to the the previous good value
                    ipTextBox.Text = chatApplication.ServerIPAddress;
            }
            else
                //If no server IP has been entered we ensure the chat application has a blank address
                chatApplication.ServerIPAddress = "";

            //Parse the port number
            if (portTextBox.Text != "")
            {
                int newPort;
                bool portParseResult = int.TryParse(portTextBox.Text, out newPort);
                if (!portParseResult || newPort < 1 || newPort > ushort.MaxValue)
                    //If the parse failed we set the portTextBox back to the previous good value
                    portTextBox.Text = chatApplication.ServerPort.ToString();
                else
                    chatApplication.ServerPort = newPort;
            }
            else
                chatApplication.ServerPort = -1;

            //Send the text entered in the input box
            chatApplication.SendMessage(input.Text);
        }

        /// <summary>
        /// Checks if the selected connection type has changed. If changed reset the example to use the new connection type.
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        void connectionType_Selected(object sender, EventArgs e)
        {
            //Parse the connection type
            string selectedItem = connectionTypeSelector.SelectedItem.ToString();
            if (selectedItem == "TCP")
                chatApplication.ConnectionType = NetworkCommsDotNet.ConnectionType.TCP;
            else if (selectedItem == "UDP")
                chatApplication.ConnectionType = NetworkCommsDotNet.ConnectionType.UDP;

            //Update the NetworkComms.Net configuration
            chatApplication.RefreshNetworkCommsConfiguration();
        }
        #endregion
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Android.App;
using Android.Content;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;

namespace ExamplesChat.Android
{
    /// <summary>
    /// All NetworkComms.Net implementation can be found here and in ChatAppBase
    /// </summary>
    public class ChatAppAndroid : ChatAppBase
    {
        #region Public Fields
        /// <summary>
        /// The chat history window. This is where all of the message appear
        /// </summary>
        public TextView ChatHistory { get; private set; }

        /// <summary>
        /// The input box where new messages are input
        /// </summary>
        public AutoCompleteTextView Input { get; private set; }

        /// <summary>
        /// The parent context of this object
        /// </summary>
        public Context ParentContext { get; private set; }
        #endregion

        #region Private Fields
        /// <summary>
        /// Handler used to post information to the parent context
        /// </summary>
        Handler handler = new Handler();
        #endregion

        /// <summary>
        /// Constructor for the Android chat app.
        /// </summary>
        public ChatAppAndroid(Context parentContext, TextView chatHistory, AutoCompleteTextView input)
            : base("Android", NetworkCommsDotNet.ConnectionType.TCP)
        {
            this.ParentContext = parentContext;
            this.ChatHistory = chatHistory;
            this.Input = input;
        }

        #region GUI Interface Overrides
        /// <summary>
        /// Append the provided message to the chatBox text box.
        /// </summary>
        /// <param name="message">Message to be appended</param>
        public override void AppendLineToChatHistory(string message)
        {
            handler.Post(() => { ChatHistory.Text += System.Environment.NewLine + message; });
        }

        /// <summary>
        /// Clear all previous chat history
        /// </summary>
        /// <param name="message">Message to be appended</param>
        public override void ClearChatHistory()
        {
            handler.Post(() => { ChatHistory.Text = ""; });
        }

        /// <summary>
        /// Clears the input text box
        /// </summary>
        public override void ClearInputLine()
        {
            handler.Post(() => { Input.Text = ""; });
        }

        /// <summary>
        /// Ouput message on error
        /// </summary>
        /// <param name="message">Message to be output</param>
        public override void ShowMessage(string message)
        {
            handler.Post(() =>
                {
                    AlertDialog dialog = (new AlertDialog.Builder(ParentContext)).Create();
                    dialog.SetCancelable(false); // This blocks the 'BACK' button  
                    dialog.SetMessage(message);
                    dialog.SetButton("OK", new EventHandler<DialogClickEventArgs>((obj, args) =>
                    {
                        dialog.Dismiss();
                    }));

                    dialog.Show();
                });
        }
        #endregion
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Android.App;
using Android.Content;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using NetworkCommsDotNet;
using DPSBase;

namespace ExamplesChat.Android
{
    /// <summary>
    /// In an attempt to keep things as clear as possible all shared implementation across chat examples
    /// has been provided in this base class.
    /// </summary>
    public abstract class ChatAppBase
    {
        #region Private Fields
        /// <summary>
        /// A boolean used to track the very first initialisation
        /// </summary>
        protected bool FirstInitialisation { get; set; }

        /// <summary>
        /// Dictionary to keep track of which peer messages have already been written to the chat window
        /// </summary>
        protected Dictionary<ShortGuid, ChatMessage> lastPeerMessageDict = new Dictionary<ShortGuid, ChatMessage>();

        /// <summary>
        /// The maximum number of times a chat message will be relayed
        /// </summary>
        int relayMaximum = 3;

        /// <summary>
        /// A local counter used to track the number of messages sent from
        /// this instance.
        /// </summary>
        long messageSendIndex = 0;

        /// <summary>
        /// An optional encryption key to use should one be required.
        /// This can be changed freely but must obviously be the same
        /// for both sender and reciever.
        /// </summary>
        string _encryptionKey = "ljlhjf8uyfln23490jf;m21-=scm20--iflmk;";
        #endregion

        #region Public Fields
        /// <summary>
        /// The type of connection currently used to send and recieve messages. Default is TCP.
        /// </summary>
        public ConnectionType ConnectionType { get; set; }

        /// <summary>
        /// The IP address of the server 
        /// </summary>
        public string ServerIPAddress { get; set; }

        /// <summary>
        /// The port of the server
        /// </summary>
        public int ServerPort { get; set; }

        /// <summary>
        /// The local name used when sending messages
        /// </summary>
        public string LocalName { get; set; }

        /// <summary>
        /// A boolean used to track if the local device is acting as a server
        /// </summary>
        public bool LocalServerEnabled { get; set; }

        /// <summary>
        /// A boolean used to track if encryption is currently being used
        /// </summary>
        public bool EncryptionEnabled { get; set; }
        #endregion

        /// <summary>
        /// Constructor for ChatAppBase
        /// </summary>
        public ChatAppBase(string name, ConnectionType connectionType)
        {
            LocalName = name;
            ConnectionType = connectionType;

            //Initialise the default values
            ServerIPAddress = "";
            ServerPort = 10000;
            LocalServerEnabled = false;
            EncryptionEnabled = false;
            FirstInitialisation = true;
        }

        #region NetworkComms.Net Methods
        /// <summary>
        /// Updates the configuration of this instance depending on set fields
        /// </summary>
        public void RefreshNetworkCommsConfiguration()
        {
            #region First Initialisation
            //On first initilisation we need to configure NetworkComms.Net to handle our incoming packet types
            //We only need to add the packet handlers once. If we call NetworkComms.Shutdown() at some future point these are not removed.
            if (FirstInitialisation)
            {
                FirstInitialisation = false;

                //Configure NetworkComms.Net to handle any incoming packet of type 'ChatMessage'
                //e.g. If we recieve a packet of type 'ChatMessage' execute the method 'HandleIncomingChatMessage'
                NetworkComms.AppendGlobalIncomingPacketHandler<ChatMessage>("ChatMessage", HandleIncomingChatMessage);

                //Configure NetworkComms.Net to perform some action when a connection is closed
                //e.g. When a connection is closed execute the method 'HandleConnectionClosed'
                NetworkComms.AppendGlobalConnectionCloseHandler(HandleConnectionClosed);
            }
            #endregion

            #region Optional Encryption
            //Configure encryption if requested
            if (EncryptionEnabled && !NetworkComms.DefaultSendReceiveOptions.DataProcessors.Contains(DPSBase.DPSManager.GetDataProcessor<DPSBase.RijndaelPSKEncrypter>()))
            {
                //Encryption is currently implemented using a pre-shared key (PSK) system
                //NetworkComms.Net supports multiple data processors which can be used with any level of granularity
                //To enable encryption globally (i.e. for all connections) we first add the encryption password as an option
                DPSBase.RijndaelPSKEncrypter.AddPasswordToOptions(NetworkComms.DefaultSendReceiveOptions.Options, _encryptionKey);
                //Finally we add the RijndaelPSKEncrypter data processor to the sendReceiveOptions
                NetworkComms.DefaultSendReceiveOptions.DataProcessors.Add(DPSBase.DPSManager.GetDataProcessor<DPSBase.RijndaelPSKEncrypter>());
            }
            else if (!EncryptionEnabled && NetworkComms.DefaultSendReceiveOptions.DataProcessors.Contains(DPSBase.DPSManager.GetDataProcessor<DPSBase.RijndaelPSKEncrypter>()))
            {
                //If encryption has been disabled but is currently enabled
                //To disable encryption we just remove the RijndaelPSKEncrypter data processor from the sendReceiveOptions
                NetworkComms.DefaultSendReceiveOptions.DataProcessors.Remove(DPSBase.DPSManager.GetDataProcessor<DPSBase.RijndaelPSKEncrypter>());
            }
            #endregion

            #region Local Server Mode and Connection Type Changes
            if (LocalServerEnabled && ConnectionType == ConnectionType.TCP && !TCPConnection.Listening())
            {
                //If we were previously listening for UDP we first shutdown comms.
                if (UDPConnection.Listening())
                {
                    AppendLineToChatHistory("Connection mode has been changed. Any existing connections will be closed.");
                    NetworkComms.Shutdown();
                }
                else
                {
                    AppendLineToChatHistory("Enabling local server mode. Any existing connections will be closed.");
                    NetworkComms.Shutdown();
                }

                //Start listening for new incoming TCP connections
                //Parameter is true so that we listen on a random port if the default is not available
                TCPConnection.StartListening(true);

                //Write the IP addresses and ports that we are listening on to the chatBox
                AppendLineToChatHistory("Listening for incoming TCP connections on:");
                foreach (var listenEndPoint in TCPConnection.ExistingLocalListenEndPoints())
                    AppendLineToChatHistory(listenEndPoint.Address + ":" + listenEndPoint.Port);

                //Add a blank line after the initialisation output
                AppendLineToChatHistory(System.Environment.NewLine);
            }
            else if (LocalServerEnabled && ConnectionType == ConnectionType.UDP && !UDPConnection.Listening())
            {
                //If we were previously listening for TCP we first shutdown comms.
                if (TCPConnection.Listening())
                {
                    AppendLineToChatHistory("Connection mode has been changed. Any existing connections will be closed.");
                    NetworkComms.Shutdown();
                }
                else
                {
                    AppendLineToChatHistory("Enabling local server mode. Any existing connections will be closed.");
                    NetworkComms.Shutdown();
                }

                //Start listening for new incoming UDP connections
                //Parameter is true so that we listen on a random port if the default is not available
                UDPConnection.StartListening(true);

                //Write the IP addresses and ports that we are listening on to the chatBox
                AppendLineToChatHistory("Listening for incoming UDP connections on:");
                foreach (var listenEndPoint in UDPConnection.ExistingLocalListenEndPoints())
                    AppendLineToChatHistory(listenEndPoint.Address + ":" + listenEndPoint.Port);

                //Add a blank line after the initialisation output
                AppendLineToChatHistory(System.Environment.NewLine);
            }
            else if (!LocalServerEnabled && (TCPConnection.Listening() || UDPConnection.Listening()))
            {
                //If the local server mode has been disabled but we are still listening we need to stop accepting incoming connections
                NetworkComms.Shutdown();
                AppendLineToChatHistory("Local server mode disabled. Any existing connections will be closed.");
                AppendLineToChatHistory(System.Environment.NewLine);
            }
            else if (!LocalServerEnabled &&
                ((ConnectionType == ConnectionType.UDP && NetworkComms.GetExistingConnection(ConnectionType.TCP).Count > 0) ||
                (ConnectionType == ConnectionType.TCP && NetworkComms.GetExistingConnection(ConnectionType.UDP).Count > 0)))
            {
                //If we are not running a local server but have changed the connection type after creating connections we need to close
                //existing connections.
                NetworkComms.Shutdown();
                AppendLineToChatHistory("Connection mode has been changed. Existing connections will be closed.");
                AppendLineToChatHistory(System.Environment.NewLine);
            }
            #endregion
        }

        /// <summary>
        /// Performs whatever functions we might so desire when we recieve an incoming ChatMessage
        /// </summary>
        /// <param name="header">The PacketHeader corresponding with the recieved object</param>
        /// <param name="connection">The Connection from which this object was recieved</param>
        /// <param name="incomingMessage">The incoming ChatMessage we are after</param>
        protected virtual void HandleIncomingChatMessage(PacketHeader header, Connection connection, ChatMessage incomingMessage)
        {
            //We only want to write a message once to the chat window
            //Because we support relaying and may recieve the same message twice from multiple sources
            //we use our history and message indexes to ensure we have a new message
            //We perform this action within a lock as HandleIncomingChatMessage could be called in parallel
            lock (lastPeerMessageDict)
            {
                if (lastPeerMessageDict.ContainsKey(incomingMessage.SourceIdentifier))
                {
                    if (lastPeerMessageDict[incomingMessage.SourceIdentifier].MessageIndex < incomingMessage.MessageIndex)
                    {
                        //If this message index is greater than the last seen from this source we can safely
                        //write the message to the ChatBox
                        AppendLineToChatHistory(incomingMessage.SourceName + " - " + incomingMessage.Message);

                        //We now replace the last recieved message with the current one
                        lastPeerMessageDict[incomingMessage.SourceIdentifier] = incomingMessage;
                    }
                }
                else
                {
                    //If we have never had a message from this source before then it has to be new
                    //by defintion
                    lastPeerMessageDict.Add(incomingMessage.SourceIdentifier, incomingMessage);
                    AppendLineToChatHistory(incomingMessage.SourceName + " - " + incomingMessage.Message);
                }
            }

            //This last section of the method is the relay feature
            //We start by checking to see if this message has already been relayed the maximum number of times
            if (incomingMessage.RelayCount < relayMaximum)
            {
                //If we are going to relay this message we need an array of 
                //all known connections, excluding the current one
                var allRelayConnections = (from current in NetworkComms.GetExistingConnection() where current != connection select current).ToArray();

                //We increment the relay count before we send
                incomingMessage.IncrementRelayCount();

                //We now send the message to every other connection
                foreach (var relayConnection in allRelayConnections)
                {
                    //We ensure we perform the send within a try catch
                    //To ensure a single failed send will not prevent the
                    //relay to all working connections.
                    try { relayConnection.SendObject("ChatMessage", incomingMessage); }
                    catch (CommsException) { /* Catch the comms exception, ignore and continue */ }
                }
            }
        }

        /// <summary>
        /// Performs whatever functions we might so desire when an existing connection is closed.
        /// </summary>
        /// <param name="connection">The closed connection</param>
        private void HandleConnectionClosed(Connection connection)
        {
            //We are going to write a message to the chat history when a connection disconnects
            //We perform the following within a lock incase mutliple connections disconnect simultaneously  
            lock (lastPeerMessageDict)
            {
                //Get the remoteIdentifier from the closed connection
                //This a unique GUID which can be used to identify peers
                ShortGuid remoteIdentifier = connection.ConnectionInfo.NetworkIdentifier;

                //If at any point we recieved a message with a matching identifier we can
                //include the peer name in the disconnection message.
                if (lastPeerMessageDict.ContainsKey(remoteIdentifier))
                    AppendLineToChatHistory("Connection with '" + lastPeerMessageDict[remoteIdentifier].SourceName + "' has been closed.");
                else
                    AppendLineToChatHistory("Connection with '" + connection.ToString() + "' has been closed.");

                //Last thing is to remove this peer from our message history
                lastPeerMessageDict.Remove(connection.ConnectionInfo.NetworkIdentifier);
            }
        }

        /// <summary>
        /// Send a message.
        /// </summary>
        public void SendMessage(string stringToSend)
        {
            //If we have tried to send a zero length string we just return
            if (stringToSend.Trim() == "") return;

            //We may or may not have entered some server connection information
            ConnectionInfo serverConnectionInfo = null;
            if (ServerIPAddress != "")
            {
                try { serverConnectionInfo = new ConnectionInfo(ServerIPAddress, ServerPort); }
                catch (Exception)
                {
                    ShowMessage("Failed to parse the server IP and port. Please ensure it is correct and try again");
                    return;
                }
            }

            //We wrap everything we want to send in the ChatMessage class we created
            ChatMessage chatMessage = new ChatMessage(NetworkComms.NetworkIdentifier, LocalName, stringToSend, messageSendIndex++);

            //We add our own message to the message history incase it gets relayed back to us
            lock (lastPeerMessageDict) lastPeerMessageDict[NetworkComms.NetworkIdentifier] = chatMessage;

            //We write our own message to the chatBox
            AppendLineToChatHistory(chatMessage.SourceName + " - " + chatMessage.Message);

            //Clear the input box text
            ClearInputLine();

            //If we provided server information we send to the server first
            if (serverConnectionInfo != null)
            {
                //We perform the send within a try catch to ensure the application continues to run if there is a problem.
                try
                {
                    if (ConnectionType == ConnectionType.TCP)
                        TCPConnection.GetConnection(serverConnectionInfo).SendObject("ChatMessage", chatMessage);
                    else if (ConnectionType == ConnectionType.UDP)
                        UDPConnection.GetConnection(serverConnectionInfo, UDPOptions.None).SendObject("ChatMessage", chatMessage);
                    else
                        throw new Exception("An invalid connectionType is set.");
                }
                catch (CommsException) { AppendLineToChatHistory("Error: A communication error occured while trying to send message to " + serverConnectionInfo + ". Please check settings and try again."); }
                catch (Exception) { AppendLineToChatHistory("Error: A general error occured while trying to send message to " + serverConnectionInfo + ". Please check settings and try again."); }
            }

            //If we have any other connections we now send the message to those as well
            //This ensures that if we are the server everyone who is connected to us gets our message
            //We want a list of all established connections not including the server if set
            List<ConnectionInfo> otherConnectionInfos;
            if (serverConnectionInfo != null)
                otherConnectionInfos = (from current in NetworkComms.AllConnectionInfo() where current.RemoteEndPoint != serverConnectionInfo.RemoteEndPoint select current).ToList();
            else
                otherConnectionInfos = NetworkComms.AllConnectionInfo();

            foreach (ConnectionInfo info in otherConnectionInfos)
            {
                //We perform the send within a try catch to ensure the application continues to run if there is a problem.
                try
                {
                    if (ConnectionType == ConnectionType.TCP)
                        TCPConnection.GetConnection(info).SendObject("ChatMessage", chatMessage);
                    else if (ConnectionType == ConnectionType.UDP)
                        UDPConnection.GetConnection(info, UDPOptions.None).SendObject("ChatMessage", chatMessage);
                    else
                        throw new Exception("An invalid connectionType is set.");
                }
                catch (CommsException) { AppendLineToChatHistory("Error: A communication error occured while trying to send message to " + info + ". Please check settings and try again."); }
                catch (Exception) { AppendLineToChatHistory("Error: A general error occured while trying to send message to " + info + ". Please check settings and try again."); }
            }

            return;
        }
        #endregion

        #region GUI Interface Methods
        /// <summary>
        /// Outputs the usage instructions to the chat window
        /// </summary>
        public void PrintUsageInstructions()
        {
            AppendLineToChatHistory("");
            AppendLineToChatHistory("Chat usage instructions:");
            AppendLineToChatHistory("");
            AppendLineToChatHistory("Step 1. Open atleast two chat applications. You can choose from Android, Windows Phone, iOS or native Windows versions.");
            AppendLineToChatHistory("Step 2. Enable local server mode in a single application, see settings.");
            AppendLineToChatHistory("Step 3. Provide remote server IP and port information in settings on remaining application.");
            AppendLineToChatHistory("Step 4. Start chatting.");
            AppendLineToChatHistory("");
            AppendLineToChatHistory("Note: Connections are established on the first message send.");
            AppendLineToChatHistory("");
        }

        /// <summary>
        /// Append the provided message to the chat history text box.
        /// </summary>
        /// <param name="message">Message to be appended</param>
        public abstract void AppendLineToChatHistory(string message);

        /// <summary>
        /// Clears the chat history
        /// </summary>
        public abstract void ClearChatHistory();

        /// <summary>
        /// Clears the input text box
        /// </summary>
        public abstract void ClearInputLine();

        /// <summary>
        /// Show a message box as an alternative to writing to the chat history
        /// </summary>
        /// <param name="message">Message to be output</param>
        public abstract void ShowMessage(string message);
        #endregion
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Android.App;
using Android.Content;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using ProtoBuf;
using NetworkCommsDotNet;

namespace ExamplesChat.Android
{
    /// <summary>
    /// A wrapper class for the messages that we intend to send and recieve. 
    /// The [ProtoContract] attribute informs NetworkCommsDotNet that we intend to 
    /// serialise (turn into bytes) this object. At the base level the 
    /// serialisation is performed by protobuf.net.
    /// </summary>
    [ProtoContract]
    public class ChatMessage
    {
        /// <summary>
        /// The source identifier of this ChatMessage.
        /// We use this variable as the constructor for the ShortGuid.
        /// The [ProtoMember(1)] attribute informs the serialiser that when
        /// an object of type ChatMessage is serialised we want to include this variable
        /// </summary>
        [ProtoMember(1)]
        string _sourceIdentifier;

        /// <summary>
        /// The source identifier is accessible as a ShortGuid
        /// </summary>
        public ShortGuid SourceIdentifier { get { return new ShortGuid(_sourceIdentifier); } }

        /// <summary>
        /// The name of the source of this ChatMessage. 
        /// We use shorthand declaration, get and set.
        /// The [ProtoMember(2)] attribute informs the serialiser that when
        /// an object of type ChatMessage is serialised we want to include this variable 
        /// </summary>
        [ProtoMember(2)]
        public string SourceName { get; private set; }

        /// <summary>
        /// The actual message.
        /// </summary>
        [ProtoMember(3)]
        public string Message { get; private set; }

        /// <summary>
        /// The index of this message. Every message sent by a particular source
        /// has an incrementing index.
        /// </summary>
        [ProtoMember(4)]
        public long MessageIndex { get; private set; }

        /// <summary>
        /// The number of times this message has been relayed.
        /// </summary>
        [ProtoMember(5)]
        public int RelayCount { get; private set; }

        /// <summary>
        /// We must include a private constructor to be used by the deserialisation step.
        /// </summary>
        public ChatMessage() { }

        /// <summary>
        /// Create a new ChatMessage
        /// </summary>
        /// <param name="sourceIdentifier">The source identifier</param>
        /// <param name="sourceName">The source name</param>
        /// <param name="message">The message to be sent</param>
        /// <param name="messageIndex">The index of this message</param>
        public ChatMessage(ShortGuid sourceIdentifier, string sourceName, string message, long messageIndex)
        {
            this._sourceIdentifier = sourceIdentifier;
            this.SourceName = sourceName;
            this.Message = message;
            this.MessageIndex = messageIndex;
            this.RelayCount = 0;
        }

        /// <summary>
        /// Increment the relay count variable
        /// </summary>
        public void IncrementRelayCount()
        {
            RelayCount++;
        }
    }
}