Imports System
Imports System.IO
Imports System.Net
Imports System.Text
Imports System.Threading
Imports System.Net.Sockets
Imports System.Windows.Forms

Class Talker
    Implements IDisposable
    '實現接口
    Public socket As socket
    '定義Socket
    Public reader As TextReader
    '定義讀出流
    Public writer As TextWriter
    '定義寫入流
    Public client As Boolean
    '標識程序是客戶端還是服務器端
    Public endPoint As IPEndPoint
    'IP地址
    Public prevSendText As String
    '在此之前發出去的信息
    Public prevReceiveText As String
    '在此之前收到的信息
    Public statusText As String
    '連接狀態
    Public statusObj As Status
    '定義Status類型變量

    Public Sub Dispose() Implements IDisposable.Dispose
        GC.SuppressFinalize(Me)
        If Not (reader Is Nothing) Then
            '這部分代碼用來釋放資源，銷毀對象
            reader.Close()
            reader = Nothing
            '釋放讀出流對象
        End If
        If Not (writer Is Nothing) Then
            writer.Close()
            '釋放寫入流對象
            writer = Nothing
        End If
        If Not (socket Is Nothing) Then
            socket.Close()
            '釋放Socket對象
            socket = Nothing
        End If
    End Sub

    Public Sub New(ByVal endPoint As IPEndPoint, ByVal client As Boolean)
        '構造函數
        Me.endPoint = endPoint
        Me.client = client
        socket = Nothing
        reader = Nothing
        writer = Nothing
        statusText = String.Empty
        prevSendText = String.Empty
        prevReceiveText = String.Empty
    End Sub

    Protected Overrides Sub Finalize()
        '析構
        Dispose()
        MyBase.Finalize()
    End Sub

    Friend Event Notifications(ByVal notify As Notification, ByVal data As Object)
    '定義【通知】事件，對notify進行處理

    Public Enum Notification
        '系統可能的通知
        Initialized = 1
        StatusChange
        ReceivedAppend
        ReceivedRefresh
        EndNotify
        ErrorNotify
    End Enum

    Public Enum Status
        '狀態
        偵聽
        已正常連接
    End Enum

    Public Sub Start()
        ThreadPool.QueueUserWorkItem(New System.Threading.WaitCallback _
        (AddressOf EstablishSocket))
        '將用戶項排隊到線程池，調用指定的委托，
        '并指定在接受線程池服務時要傳遞給委托的對象()
    End Sub

    Private Sub EstablishSocket(ByVal state As Object)
        Dim stream As NetworkStream
        '定義流
        stream = Nothing
        '初始化
        Try
            If Not client Then
                '如果不是客戶端，則進行偵聽
                Dim listener As Socket
                Try
                    listener = New Socket(AddressFamily.InterNetwork, _
                    SocketType.Stream, ProtocolType.Tcp)
                    '實例化Socket類
                    listener.Blocking = True
                    '指示Socket處于阻塞模式
                    listener.Bind(endPoint)
                    '綁定本地的IP地址
                    SetStatus(Status.偵聽)
                    '顯示狀態
                    listener.Listen(0)
                    '偵聽
                    socket = listener.Accept()
                    '處理傳入的連接請求
                    listener.Close()
                    '關閉Socket連接
                    stream = New NetworkStream(socket)
                    '實例化流類
                    reader = New StreamReader(stream)
                    '實例化讀出流類
                    writer = New StreamWriter(stream)
                    '實例化寫入流類
                    writer.Write("WINTALK .NET")
                    writer.Flush()
                    '清理緩沖區,將所有的緩沖數據寫入基礎設備
                Catch e As SocketException
                    '如果已經存在了一個偵聽端，那么這個端口作為客戶端
                    If e.ErrorCode = 10048 Then
                        client = True
                        endPoint = New IPEndPoint _
                        (Dns.Resolve("127.0.0.1").AddressList(0), endPoint.Port)
                        '設置端口地址
                    Else
                        RaiseEvent Notifications _
                        (Notification.ErrorNotify, "初始化Socket時發生錯誤:" & ControlChars.CrLf & e.ToString())
                        '觸發事件
                    End If
                End Try
            End If

            If client Then  '以客戶端形式進行連接
                Dim temp As New Socket(AddressFamily.InterNetwork, _
                SocketType.Stream, ProtocolType.Tcp)
                '實例化Socket類
                temp.Blocking = True
                '指示Socket處于阻塞模式
                temp.Connect(endPoint)
                socket = temp
                socket.SetSocketOption(SocketOptionLevel.Socket, _
                SocketOptionName.ReceiveTimeout, 5000)
                socket.SetSocketOption(SocketOptionLevel.Socket, _
                SocketOptionName.SendTimeout, 5000)
                stream = New NetworkStream(socket)
                reader = New StreamReader(stream)
                writer = New StreamWriter(stream)
                Dim handshake(11) As Char
                '判斷是否連接上，通過發出的 WINTALK .NET 消息來判斷
                Try
                    If Not (reader.Read(handshake, 0, 12) > 0 And New _
                    String(handshake) = "WINTALK .NET") Then
                        socket.Close()
                        socket = Nothing
                    Else
                        socket.SetSocketOption(SocketOptionLevel.Socket, _
                        SocketOptionName.ReceiveTimeout, 0)
                        socket.SetSocketOption(SocketOptionLevel.Socket, _
                        SocketOptionName.SendTimeout, 0)
                    End If
                Catch
                    socket.Close()
                    socket = Nothing
                End Try
            End If
            If Not (socket Is Nothing) Then
                SetStatus(Status.已正常連接)
                RaiseEvent Notifications(Notification.Initialized, Me)
                '觸發事件進行初始化
                ReceiveTalk() '開始收取信息
                RaiseEvent Notifications(Notification.EndNotify, "遠程連接已經關閉")
            Else
                RaiseEvent Notifications(Notification.ErrorNotify, _
                "建立Socket失敗，檢查端口設置是否正確")
            End If
        Catch e As IOException
            Dim sockExcept As SocketException = _
            CType(e.InnerException, SocketException)
            If Not (sockExcept Is Nothing) And 10054 = sockExcept.ErrorCode Then
                RaiseEvent Notifications(Notification.EndNotify, "遠程連接已經斷開")
            Else
                RaiseEvent Notifications(Notification.ErrorNotify, "Socket 錯誤" & _
                ControlChars.CrLf & e.Message)
            End If
        Catch e As Exception
            RaiseEvent Notifications(Notification.ErrorNotify, "Socket 錯誤" & _
            ControlChars.CrLf & e.Message)
        End Try
    End Sub

    Public Sub SendTalk(ByVal newText As String)
        '向遠程機器發送信息
        Dim send As String
        If prevSendText.Length <= newText.Length And _
        String.CompareOrdinal(newText, 0, prevSendText, 0, _
        prevSendText.Length) = 0 Then
            '判斷是否是附加的字符串
            Dim append As [String] = newText.Substring(prevSendText.Length)
            send = String.Format("A{0}:{1}", append.Length, append)
        Else
            send = String.Format("R{0}:{1}", newText.Length, newText)
            '否則取代該字符串
        End If '
        writer.Write(send)
        '發送字符串
        writer.Flush()
        '清理緩沖區
        prevSendText = newText
        '保存字符串為后面作比較
    End Sub

    Private Sub SetStatus(ByVal statusObj As Status)
        Me.statusObj = statusObj
        '獲取系統狀態
        RaiseEvent Notifications(Notification.StatusChange, statusObj)
        '設置狀態
    End Sub

    Private Sub ReceiveTalk()
        '從遠程客戶端獲取信息
        Dim commandBuffer(19) As Char
        Dim oneBuffer(0) As Char
        Dim readMode As Integer = 1
        Dim counter As Integer = 0
        Dim textObj As New StringBuilder()
        While readMode <> 0
            If reader.Read(oneBuffer, 0, 1) = 0 Then
                readMode = 0
            Else
                Select Case readMode
                    Case 1
                        If counter = commandBuffer.Length Then
                            readMode = 0
                        End If
                        If oneBuffer(0) <> ":"c Then
                            commandBuffer(counter) = oneBuffer(0)
                            counter = counter + 1
                        Else
                            counter = Convert.ToInt32(New String(commandBuffer, 1, _
                            counter - 1))
                            If counter > 0 Then
                                readMode = 2
                                textObj.Length = 0
                            Else
                                If commandBuffer(0) = "R"c Then
                                    counter = 0
                                    prevReceiveText = String.Empty
                                    RaiseEvent Notifications _
                                    (Notification.ReceivedRefresh, prevReceiveText)
                                End If
                            End If
                        End If
                    Case 2
                        textObj.Append(oneBuffer(0))
                        counter = counter - 1
                        If counter = 0 Then
                            Select Case commandBuffer(0)
                                Case "R"c
                                    prevReceiveText = textObj.ToString()
                                    RaiseEvent Notifications _
                                    (Notification.ReceivedRefresh, prevReceiveText)
                                Case Else
                                    Dim newText As String
                                    newText = textObj.ToString()
                                    prevReceiveText += newText
                                    RaiseEvent Notifications _
                                    (Notification.ReceivedAppend, newText)
                            End Select
                            readMode = 1
                        End If
                    Case Else
                        readMode = 0
                End Select
            End If
        End While
    End Sub

End Class