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文件:      Wintalk.vb
'  摘要:   演示如何使用.NET Framework library创建聊天程序.

Option Explicit On
Option Strict On

Imports System
Imports System.IO
Imports System.Text
Imports System.Threading
Imports System.Net
Imports System.Net.Sockets
Imports System.Drawing
Imports System.Windows.Forms
Imports Microsoft.VisualBasic

Class App
    'Entry point which delegates to C-style main Private Function
    Public Overloads Shared Sub Main()
    End Sub
    ' Entry point
    Overloads Public Shared Sub Main(args() As String)
        ' If the args parse in known way then run the app
        If ParseArgs(args) Then
            ' Create a custom Talker object
            Dim talkerObj As New Talker(endPoint, client)
            ' Pass the object reference to a new form object
            Dim form As New TalkForm(talkerObj)
            ' Start the talker "talking"
            ' Run the applications message pump
        End If
    End Sub 'Main
    ' Parsed Argument Storage
    Private Shared endPoint As IPEndPoint
    Private Shared client As Boolean
    ' Parse command line arguments
    Private Shared Function ParseArgs(args() As String) As Boolean
            If args.Length = 1 Then
                client = False
                endPoint = New IPEndPoint(IPAddress.Any, 5150)
                Return True
            End If
            Dim port As Integer
            Select Case Char.ToUpper(args(1).ToCharArray()(1))
                Case "L"c
                    port = 5150
                    If args.Length > 2 Then
                        port = Convert.ToInt32(args(2))
                    End If
                    endPoint = New IPEndPoint(IPAddress.Any, port)
                    client = False
                Case "C"c
                    port = 5150
                    Dim address As String = ""
                    client = True
                    If args.Length > 2 Then
                        address = args(2)
                        port = Convert.ToInt32(args(3))
                    End If
                    endPoint = New IPEndPoint(Dns.Resolve(address).AddressList(0), port)
                Case Else
                        Return False
            End Select
        End Try
        Return True
    End Function 'ParseArgs
    ' Show sample usage
    Private Shared Sub ShowUsage()
        MessageBox.Show("WinTalk [switch] [parameters...]" & ControlChars.CrLf & ControlChars.CrLf & _
            "  /L  [port]" & ControlChars.Tab & ControlChars.Tab & "-- Listens on a port.  Default:  5150" & ControlChars.CrLf & _
            "  /C  [address] [port]" & ControlChars.Tab & "-- Connects to an address and port." & ControlChars.CrLf & ControlChars.CrLf & _
            "Example Server - " & ControlChars.CrLf & _
            "Wintalk /L" & ControlChars.CrLf & ControlChars.CrLf & _
            "Example Client - " & ControlChars.CrLf & _
            "Wintalk /C ServerMachine 5150", "WinTalk Usage")
    End Sub 'ShowUsage
End Class 'App

' UI class for the sample
Class TalkForm
    Inherits Form
    Public Sub New(talkerObj As Talker)
        ' Associate for method with the talker object
        Me.talkerObj = talkerObj
        AddHandler talkerObj.Notifications, AddressOf HandleTalkerNotifications
        ' Create a UI elements
        Dim talkSplitter As New Splitter()
        Dim talkPanel As New Panel()

        receiveText = New TextBox()
        sendText = New TextBox()
        'we'll support up to 64k data in our text box controls
        receiveText.MaxLength = 65536
        sendText.MaxLength = 65536
        statusText = New Label()
        ' Initialize UI elements
        receiveText.Dock = DockStyle.Top
        receiveText.Multiline = True
        receiveText.ScrollBars = ScrollBars.Both
        receiveText.Size = New Size(506, 192)
        receiveText.TabIndex = 1
        receiveText.Text = ""
        receiveText.WordWrap = False
        receiveText.ReadOnly = True
        talkPanel.Anchor = AnchorStyles.Top Or AnchorStyles.Bottom Or AnchorStyles.Left Or AnchorStyles.Right
        talkPanel.Controls.AddRange(New Control() {sendText, talkSplitter, receiveText})
        talkPanel.Size = New Size(506, 371)
        talkPanel.TabIndex = 0
        talkSplitter.Dock = DockStyle.Top
        talkSplitter.Location = New Point(0, 192)
        talkSplitter.Size = New Size(506, 6)
        talkSplitter.TabIndex = 2
        talkSplitter.TabStop = False
        statusText.Dock = DockStyle.Bottom
        statusText.Location = New Point(0, 377)
        statusText.Size = New Size(507, 15)
        statusText.TabIndex = 1
        statusText.Text = "Status:"
        sendText.Dock = DockStyle.Fill
        sendText.Location = New Point(0, 198)
        sendText.Multiline = True
        sendText.ScrollBars = ScrollBars.Both
        sendText.Size = New Size(506, 173)
        sendText.TabIndex = 0
        sendText.Text = ""
        sendText.WordWrap = False
        AddHandler sendText.TextChanged, AddressOf HandleTextChange
        sendText.Enabled = False
        AutoScaleBaseSize = New Size(5, 13)
        ClientSize = New Size(507, 392)
        Controls.AddRange(New Control() {statusText, talkPanel})
        Me.Text = "WinTalk"

        Me.ActiveControl = sendText
    End Sub 'New
    ' When the app closes, dispose of the talker object
    Protected Overrides Sub OnClosed(e As EventArgs)
        If Not (talkerObj Is Nothing) Then
            RemoveHandler talkerObj.Notifications, AddressOf HandleTalkerNotifications
        End If
    End Sub 'OnClosed
    ' Handle notifications from the talker object
    Private Sub HandleTalkerNotifications(notify As Talker.Notification, data As Object)
        Select Case notify
            Case Talker.Notification.Initialized
                ' Respond to status changes
            Case Talker.Notification.StatusChange
                Dim statusObj As Talker.Status = CType(data, Talker.Status)
                statusText.Text = String.Format("Status: {0}", statusObj)
                If statusObj = Talker.Status.Connected Then
                    sendText.Enabled = True
                End If
                ' Respond to received text
            Case Talker.Notification.Received
                receiveText.Text = data.ToString()
                receiveText.SelectionStart = Int32.MaxValue
                ' Respond to error notifications
            Case Talker.Notification.ErrorNotify
                ' Respond to end
            Case Talker.Notification.EndNotify
                MessageBox.Show(data.ToString(), "Closing WinTalk")
            Case Else
        End Select
    End Sub 'HandleTalkerNotifications
    ' Handle text change notifications and send talk
    Private Sub HandleTextChange(sender As Object, e As EventArgs)
        If Not (talkerObj Is Nothing) Then
            talkerObj.SendTalk(CType(sender, TextBox).Text)
        End If
    End Sub 'HandleTextChange
    ' Close with an explanation
    Private OverLoads Sub Close(message As String)
        MessageBox.Show(message, "Error!")
    End Sub 'Close
    ' Private UI elements
    Private receiveText As TextBox
    Private sendText As TextBox
    Private statusText As Label
    Private talkerObj As Talker

    Private Sub TalkForm_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

    End Sub

    Private Sub InitializeComponent()
        Me.AutoScaleBaseSize = New System.Drawing.Size(6, 14)
        Me.ClientSize = New System.Drawing.Size(292, 273)
        Me.Name = "TalkForm"

    End Sub
End Class 'TalkForm

' An encapsulation of the Sockets class used for socket chatting
Class Talker
    Implements IDisposable
    ' Construct a talker
    Public Sub New(endPoint As IPEndPoint, client As Boolean)
        Me.endPoint = endPoint
        Me.client = client
        socket = Nothing
        reader = Nothing
        writer = Nothing
        statusText = String.Empty
        prevSendText = String.Empty
        prevReceiveText = String.Empty
    End Sub 'New
    ' Finalize a talker
    Overrides Protected Sub Finalize()
    End Sub 'Finalize
    ' Dispose of resources and surpress finalization
    Public Sub Dispose() Implements IDisposable.Dispose
        If Not (reader Is Nothing) Then
            reader = Nothing
        End If
        If Not (writer Is Nothing) Then
            writer = Nothing
        End If
        If Not (socket Is Nothing) Then
            socket = Nothing
        End If
    End Sub 'Dispose
    ' Nested delegate class and matchine event
    Delegate Sub NotificationCallback(notify As Notification, data As Object)
    Public Event Notifications As NotificationCallback
    ' Nested enum for notifications
    Public Enum Notification
        Initialized = 1
    End Enum 'Notification
    ' Nested enum for supported states
    Public Enum Status
    End Enum 'Status
    ' Start up the talker's functionality
    Public Sub Start()
        ThreadPool.QueueUserWorkItem(New System.Threading.WaitCallback(AddressOf EstablishSocket))
    End Sub 'Start
    ' Establish a socket connection and start receiving
    Private Sub EstablishSocket(ByVal state As Object)
            ' If not client, setup listner
            If Not client Then
                Dim listener As Socket

                    listener = New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
                    listener.Blocking = True
                    socket = listener.Accept()
                Catch e As SocketException
                    ' If there is already a listener on this port try client
                    If e.ErrorCode = 10048 Then
                        client = True
                        endPoint = New IPEndPoint(Dns.Resolve("").AddressList(0), endPoint.Port)
                        RaiseEvent Notifications(Notification.ErrorNotify, "Error Initializing Socket:" & ControlChars.CrLf & e.ToString())
                    End If
                End Try
            End If

            ' Try a client connection
            If client Then
                Dim temp As New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
                temp.Blocking = True
                socket = temp
            End If

            ' If it all worked out, create stream objects
            If Not (socket Is Nothing) Then
                Dim stream As New NetworkStream(socket)
                reader = New StreamReader(stream)
                writer = New StreamWriter(stream)
                RaiseEvent Notifications(Notification.Initialized, Me)
                RaiseEvent Notifications(Notification.ErrorNotify, "Failed to Establish Socket")
            End If

            ' Start receiving talk
            ' Note: on w2k and later platforms, the NetworkStream.Read()
            ' method called in ReceiveTalke will generate an exception when
            ' the remote connection closes. We handle this case in our
            ' catch block below.

            ' On Win9x platforms, NetworkStream.Read() returns 0 when
            ' the remote connection closes, prompting a graceful return
            ' from ReceiveTalk() above. We will generate a Notification.End
            ' message here to handle the case and shut down the remaining
            ' WinTalk instance.
            RaiseEvent Notifications(Notification.EndNotify, "Remote connection has closed.")
        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, "Remote connection has closed.")
                RaiseEvent Notifications(Notification.ErrorNotify, "Socket Error:" & ControlChars.CrLf & e.Message)
            End If
        Catch e As Exception
            RaiseEvent Notifications(Notification.ErrorNotify, "Socket Error:" & ControlChars.CrLf & e.Message)
        End Try
    End Sub 'EstablishSocket

    ' Send text to remote connection
    Public Sub SendTalk(ByVal newText As String)
        Dim send As String
        ' Is this an append
        If prevSendText.Length <= newText.Length And String.CompareOrdinal(newText, 0, prevSendText, 0, prevSendText.Length) = 0 Then
            Dim append As [String] = newText.Substring(prevSendText.Length)
            send = String.Format("A{0}:{1}", append.Length, append)
            ' or a complete replacement
            send = String.Format("R{0}:{1}", newText.Length, newText)
        End If
        ' Send the data and flush it out
        ' Save the text for future comparison
        prevSendText = newText
    End Sub 'SendTalk

    ' Send a status notification
    Private Sub SetStatus(ByVal statusObj As Status)
        Me.statusObj = statusObj
        RaiseEvent Notifications(Notification.StatusChange, statusObj)
    End Sub 'SetStatus

    ' Receive chat from remote client
    Private Sub ReceiveTalk()
        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
                Goto ContinueWhile1
            End If

            Select Case readMode
                Case 1
                    If counter = commandBuffer.Length Then
                        readMode = 0
                        Goto ContinueWhile1
                    End If
                    If oneBuffer(0) <> ":"c Then
                        commandBuffer(counter) = oneBuffer(0)
                        counter = counter + 1
                        counter = Convert.ToInt32(New String(commandBuffer, 1, counter - 1))
                        If counter > 0 Then
                            readMode = 2
                            textObj.Length = 0
                            If commandBuffer(0) = "R"c Then
                                counter = 0
                                prevReceiveText = String.Empty
                                RaiseEvent Notifications(Notification.Received, prevReceiveText)
                            End If
                        End If
                    End If
                Case 2
                    counter = counter - 1
                    If counter = 0 Then
                        Select Case commandBuffer(0)
                            Case "R"c
                                prevReceiveText = textObj.ToString()
                            Case Else
                                prevReceiveText += textObj.ToString()
                        End Select
                        readMode = 1

                        RaiseEvent Notifications(Notification.Received, prevReceiveText)
                    End If
                Case Else
                    readMode = 0
                    Goto ContinueWhile1
            End Select
        End While
    End Sub 'ReceiveTalk

    Private socket As socket

    Private reader As TextReader
    Private writer As TextWriter

    Private client As Boolean
    Private endPoint As IPEndPoint

    Private prevSendText As String
    Private prevReceiveText As String
    Private statusText As String

    Private statusObj As Status
End Class 'Talker

.NET Framework SDK有这个例子.


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