P2P by using WCF

P2P by using WCF
這是一個用C# 寫的應用，主要是練習 P2P，使用的是 .NET 3.0 推出的 WCF，可以參考 A simple peer to peer chat application using WCF netPeerTcpBinding。若對開啟 C# 應用有興趣的人，可以參考 Button Controls。P2P 可以想成一個應用程式本身具有 Client 及 Server。

Server

在 Server 端需要額外引入三個 namespace:

    * System.ServiceModel;
    * System.ServiceModel.Channels;
    * System.ServiceModel.PeerResolvers; 

完整程式碼如下:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.ServiceModel;
using System.ServiceModel.Channels;
using System.ServiceModel.PeerResolvers;

namespace ChatServer
{
    public partial class ChatServer : Form
    {
        private CustomPeerResolverService cprs;
        private ServiceHost host;

        public ChatServer()
        {
            InitializeComponent();            
            btnStop.Enabled = false;
        }

        private void btnStart_Click(object sender, EventArgs e)
        {
            try
            {
                cprs = new CustomPeerResolverService();
                cprs.RefreshInterval = TimeSpan.FromSeconds(5);
                host = new ServiceHost(cprs);
                cprs.ControlShape = true;
                cprs.Open();
                host.Open(TimeSpan.FromDays(1000000));
                lblMessage.Text = "Server started successfully.";
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString());
            }
            finally
            {
                btnStart.Enabled = false;
                btnStop.Enabled = true;
            }
        }

        private void btnStop_Click(object sender, EventArgs e)
        {
            try
            {
                cprs.Close();
                host.Close();
                lblMessage.Text = "Server stopped successfully.";
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString());
            }
            finally
            {
                btnStart.Enabled = true;
                btnStop.Enabled = false;
            }
        }
    }
} 

很簡單，若真的要說程式片斷就在前面的六行:

                cprs = new CustomPeerResolverService();
                cprs.RefreshInterval = TimeSpan.FromSeconds(5);
                host = new ServiceHost(cprs);
                cprs.ControlShape = true;
                cprs.Open();
                host.Open(TimeSpan.FromDays(1000000));

cprs 是 CustomPeerResolverService 物件，用來當 ServiceHost 物件的輸入參數，主要會讀取一個設定檔(App.config), 並且設定連線資訊更新時間是 5ms。
host 是 ServiceHost 物件，並設定 timeout 時間為永不停止(1000000 天實在是非常久的時間)。然後....就這樣.....

CONFIG

至於設定檔，內容如下:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <system.serviceModel>
    <services>
      <service name="System.ServiceModel.PeerResolvers.CustomPeerResolverService">
        <host>
          <baseAddresses>
            <add baseAddress="net.tcp://localhost/ChatServer"/>
          </baseAddresses>
        </host>
        <endpoint address="net.tcp://localhost/ChatServer" binding="netTcpBinding"
                  bindingConfiguration="TcpConfig"
                  contract="System.ServiceModel.PeerResolvers.IPeerResolverContract">         
        </endpoint>         
      </service>
    </services>

    <bindings>
      <netTcpBinding>
        <binding name="TcpConfig">
          <security mode="None"></security>
        </binding>
      </netTcpBinding>
    </bindings>
  </system.serviceModel>
</configuration>

Client

Client 是稍微複雜了點，先貼一下原始程式碼如下，只需要用到兩個 namespace(System.ServiceModel, 及System.ServiceModel.Channels):

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.ServiceModel;
using System.ServiceModel.Channels;

namespace ChatClient
{
    [ServiceContract(CallbackContract = typeof(IChatService))]
    public interface IChatService
    {
        [OperationContract(IsOneWay = true)]
        void Join(string memberName);
        [OperationContract(IsOneWay = true)]
        void Leave(string memberName);
        [OperationContract(IsOneWay = true)]
        void SendMessage(string memberName, string message);
    }

    public interface IChatChannel : IChatService, IClientChannel
    {
    }

    public partial class ChatClient : Form, IChatService
    {
        private delegate void UserJoined(string name);
        private delegate void UserSendMessage(string name, string message);
        private delegate void UserLeft(string name);

        private static event UserJoined NewJoin;
        private static event UserSendMessage MessageSent;
        private static event UserLeft RemoveUser;
               
        private string userName;
        private IChatChannel channel;
        private DuplexChannelFactory factory;

        public ChatClient()
        {
            InitializeComponent();
            this.AcceptButton = btnLogin;
        }

        public ChatClient(string userName)
        {
            this.userName = userName;
        }

        private void btnLogin_Click(object sender, EventArgs e)
        {
            if (!string.IsNullOrEmpty(txtUserName.Text.Trim()))
            {
                try
                {
                    NewJoin += new UserJoined(ChatClient_NewJoin);
                    MessageSent += new UserSendMessage(ChatClient_MessageSent);
                    RemoveUser += new UserLeft(ChatClient_RemoveUser);

                    channel = null;
                    this.userName = txtUserName.Text.Trim();
                    InstanceContext context = new InstanceContext(
                        new ChatClient(txtUserName.Text.Trim()));
                    factory =
                        new DuplexChannelFactory(context, "ChatEndPoint");
                    channel = factory.CreateChannel();
                    IOnlineStatus status = channel.GetProperty();
                    status.Offline += new EventHandler(Offline);
                    status.Online += new EventHandler(Online);                   
                    channel.Open();                   
                    channel.Join(this.userName);
                    grpMessageWindow.Enabled = true;
                    grpUserList.Enabled = true;                   
                    grpUserCredentials.Enabled = false;                   
                    this.AcceptButton = btnSend;
                    rtbMessages.AppendText("*****************************WEL-COME to Chat Application*****************************\r\n");
                    txtSendMessage.Select();
                    txtSendMessage.Focus();
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.ToString());
                }
            }
        }

        void ChatClient_RemoveUser(string name)
        {
            try
            {
                rtbMessages.AppendText("\r\n");
                rtbMessages.AppendText(name + " left at " + DateTime.Now.ToString());
                lstUsers.Items.Remove(name);
            }
            catch (Exception ex)
            {
                System.Diagnostics.Trace.WriteLine(ex.ToString());
            }
        }

        void ChatClient_MessageSent(string name, string message)
        {
            if (!lstUsers.Items.Contains(name))
            {
                lstUsers.Items.Add(name);
            }
            rtbMessages.AppendText("\r\n");
            rtbMessages.AppendText(name + " says: " + message);
        }

        void ChatClient_NewJoin(string name)
        {
            rtbMessages.AppendText("\r\n");
            rtbMessages.AppendText(name + " joined at: [" + DateTime.Now.ToString() + "]");           
            lstUsers.Items.Add(name);      
        }

        void Online(object sender, EventArgs e)
        {           
            rtbMessages.AppendText("\r\nOnline: " + this.userName);
        }

        void Offline(object sender, EventArgs e)
        {
            rtbMessages.AppendText("\r\nOffline: " + this.userName);
        }

        #region IChatService Members

        public void Join(string memberName)
        {           
            if (NewJoin != null)
            {
                NewJoin(memberName);
            }
        }

        public new void Leave(string memberName)
        {
            if (RemoveUser != null)
            {
                RemoveUser(memberName);
            }
        }

        public void SendMessage(string memberName, string message)
        {
            if (MessageSent != null)
            {
                MessageSent(memberName, message);
            }
        }

        #endregion

        private void btnSend_Click(object sender, EventArgs e)
        {
            channel.SendMessage(this.userName, txtSendMessage.Text.Trim());
            txtSendMessage.Clear();
            txtSendMessage.Select();
            txtSendMessage.Focus();
        }

        private void ChatClient_FormClosing(object sender, FormClosingEventArgs e)
        {
            try
            {
                if (channel != null)
                {
                    channel.Leave(this.userName);
                    channel.Close();
                }
                if (factory != null)
                {
                    factory.Close();
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString());
            }
        }
    }
}

雖然小小長了點，可以看到 interface 中只有定義了三個動作:

        Join : 用來登入用
        Leave: 用來登出用
        SendMessage:  用來傳送訊息

在繼續看這份 souce code 之前，先來讀一下設定檔:

Config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <system.serviceModel>
    <client>
      <endpoint name="ChatEndPoint" address="net.p2p://chatMesh/ChatServer"
                binding="netPeerTcpBinding" bindingConfiguration="PeerTcpConfig"
                contract="ChatClient.IChatService"></endpoint>
   </client>

    <bindings>
      <netPeerTcpBinding>
        <binding name="PeerTcpConfig" port="0">
          <security mode="None"></security>
          <resolver mode="Custom">
            <custom address="net.tcp://localhost/ChatServer" binding="netTcpBinding"
                    bindingConfiguration="TcpConfig"></custom>
          </resolver>
        </binding>
      </netPeerTcpBinding>
      <netTcpBinding>
        <binding name="TcpConfig">
          <security mode="None"></security>
        </binding>
      </netTcpBinding>
    </bindings>
  </system.serviceModel>
</configuration>

對應到前面講的 Join, Leave, SendMessage 三個介面，需要三個事件來配合:

        private static event UserJoined NewJoin;
        private static event UserSendMessage MessageSent;
        private static event UserLeft RemoveUser;

Event 的使用在程式中如下:

                    NewJoin += new UserJoined(ChatClient_NewJoin);
                    MessageSent += new UserSendMessage(ChatClient_MessageSent);
                    RemoveUser += new UserLeft(ChatClient_RemoveUser);

聊天室功能裡面，最重要的就是聊天，對，有點廢話，不過難就難在網路連線的維護，幸好都被 WCF 做掉了，在程式裡面是透過 DuplexChannelFactory() 物件來達成:

               factory = new DuplexChannelFactory(context, "ChatEndPoint");
               channel = factory.CreateChannel();

若我們看看幾個動作即可明白中間的關聯:

channel.Join(this.userName);
channel.SendMessage(this.userName, txtSendMessage.Text.Trim());
channel.Leave(this.userName);
channel.Close();

好了，就這樣。什麼？沒講完？對，聰明的你一定有發現，好像沒指出收訊息的機制？呵，其實是沒特別講清楚而已。

訊息收送

收: MessageSent += new UserSendMessage(ChatClient_MessageSent);
送: channel.SendMessage(this.userName, txtSendMessage.Text.Trim());