TCP应答窗口演示

最新推荐文章于 2025-08-11 09:11:08 发布
原创最新推荐文章于 2025-08-11 09:11:08 发布 · 297 阅读
CC 4.0 BY-SA版权
本程序演示了TCP应答窗口的工作原理。
Public Class Form1
    Const POS_TOP = 32
    Const POS_BOTT = 200
    Const TMR_MAX = 2000
    Const POS_WIDTH = 20
    Const POS_WIDTHW = 24

    Dim POS_STEP As Integer

    Dim TXWin As Integer
    Dim RXWin As Integer
    Dim WinSize As Integer
    Dim WinsizeR As Integer

    Dim Pkg_RcvR(20) As Integer
    Dim Pkg_RcvT(20) As Integer
    Dim Pkg_Sent(20) As Integer
    Dim TopLabel() As Label
    Dim BottomLabel() As Label
    Dim PkgLabel() As Label
    Dim TmrLabel() As Label

    Dim Pkg_Dir(20) As Integer      '数据包运动方向变量
    Dim Tmr_Cnt(20) As Integer      '数据包超时计数

    Dim Lab_Dir As Boolean

    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles tmr_Global.Tick
        Dim i As Integer
        For i = 1 To 20
            If Pkg_Dir(i) = 1 Then PkgLabel(i).Top = PkgLabel(i).Top + POS_STEP
            If Pkg_Dir(i) = -1 Then PkgLabel(i).Top = PkgLabel(i).Top - POS_STEP
            If PkgLabel(i).Top >= POS_BOTT Then
                If i < RXWin Or i >= RXWin + WinsizeR Then
                    Pkg_Dir(i) = 0
                    PkgLabel(i).Visible = False
                    PkgLabel(i).Top = POS_TOP
                Else
                    Pkg_Dir(i) = -1
                    PkgLabel(i).BackColor = Color.Yellow
                    BottomLabel(i).BackColor = Color.Yellow
                    PkgLabel(i).Top = POS_BOTT
                    Pkg_RcvR(i) = 1
                End If
            End If

                If PkgLabel(i).Top <= POS_TOP And Pkg_Dir(i) = -1 Then
                    Pkg_Dir(i) = 0
                    PkgLabel(i).Visible = False
                    If i < TXWin Or i >= TXWin + WinSize Then
                        'TopLabel(i).BackColor = Color.White
                    Else
                        TopLabel(i).BackColor = Color.Red
                        PkgLabel(i).Top = POS_TOP
                        Pkg_RcvT(i) = 1
                    End If

                End If

                If Pkg_RcvT(i) = 0 Then Tmr_Cnt(i) = Tmr_Cnt(i) - 3

                If (Tmr_Cnt(i) <= 0) Then
                    Tmr_Cnt(i) = 0
                    If (Pkg_RcvT(i) = 0 And Pkg_Sent(i) = 1) Then

                        Pkg_Dir(i) = 1
                        PkgLabel(i).Top = POS_TOP
                        PkgLabel(i).BackColor = Color.Red
                        PkgLabel(i).Visible = True
                        Tmr_Cnt(i) = TMR_MAX
                        Beep()
                    End If
                End If

                TmrLabel(i).Text = Int(Tmr_Cnt(i) / 100)
        Next
        For i = 1 To 20
            If Pkg_RcvT(i) = 0 Then Exit For
        Next
        TXWin = i
        ShowLabel1(TXWin)

        For i = 1 To 20
            If Pkg_RcvR(i) = 0 Then Exit For
        Next
        RXWin = i
        ShowLabel2(RXWin)

        TextBox1.Text = "T:" & TXWin
        TextBox2.Text = "R:" & RXWin

        If (TXWin >= 21) Then
            tmr_Global.Enabled = False
            btnSend.Enabled = False
            btnPause.Enabled = False
            btnKill.Enabled = False
            MsgBox("所有的数据都已成功发送完毕并收到应答。", MsgBoxStyle.Information, "恭喜你")
        End If
    End Sub

    Private Sub PkgLabel_Click(ByVal sender As Object, ByVal e As EventArgs)
        Dim i As Integer
        For i = 1 To 20
            If sender.Equals(PkgLabel(i)) = True Then
                PkgLabel(i).BackColor = Color.Cyan
            End If
        Next
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim i As New Integer
        ReDim TopLabel(20)
        ReDim BottomLabel(20)
        ReDim PkgLabel(20)
        ReDim TmrLabel(20)

        POS_STEP = 1

        For i = 1 To 20
            PkgLabel(i) = New Label
            TopLabel(i) = New Label
            BottomLabel(i) = New Label

            PkgLabel(i).Left = POS_WIDTHW * i
            PkgLabel(i).Width = POS_WIDTH
            PkgLabel(i).Height = 16
            PkgLabel(i).BorderStyle = BorderStyle.FixedSingle
            AddHandler PkgLabel(i).Click, AddressOf PkgLabel_Click

            TmrLabel(i) = New Label
            TmrLabel(i).Left = POS_WIDTHW * i
            TmrLabel(i).Top = 12
            TmrLabel(i).Width = POS_WIDTH
            TmrLabel(i).Height = 16
            TmrLabel(i).BackColor = Color.White
            TmrLabel(i).BorderStyle = BorderStyle.FixedSingle


            TopLabel(i).Left = POS_WIDTHW * i
            TopLabel(i).Top = POS_TOP
            TopLabel(i).Width = POS_WIDTH
            TopLabel(i).Height = 16
            TopLabel(i).BorderStyle = BorderStyle.FixedSingle

            BottomLabel(i).Left = POS_WIDTHW * i
            BottomLabel(i).Top = POS_BOTT
            BottomLabel(i).Width = POS_WIDTH
            BottomLabel(i).Height = 16
            BottomLabel(i).BorderStyle = BorderStyle.FixedSingle

            Me.Controls.Add(PkgLabel(i))
            Me.Controls.Add(TmrLabel(i))
            Me.Controls.Add(TopLabel(i))
            Me.Controls.Add(BottomLabel(i))
        Next
        Reset_All()
    End Sub

    Private Sub Reset_All()
        Dim i As Integer
        TXWin = 1
        RXWin = 1
        For i = 1 To 20
            Pkg_RcvR(i) = 0
            Pkg_RcvT(i) = 0
            Pkg_Sent(i) = 0
            Pkg_Dir(i) = 0
            Tmr_Cnt(i) = 0
            PkgLabel(i).Top = POS_TOP
            PkgLabel(i).BackColor = Color.Red
            PkgLabel(i).Visible = False
            TopLabel(i).BackColor = Color.White
            BottomLabel(i).BackColor = Color.Blue
            WinSize = Num1.Value
            WinsizeR = Num2.Value
        Next
        ShowLabel1(1)
        ShowLabel2(1)
        Label1.SendToBack()
        Label2.SendToBack()
        tmr_Global.Enabled = True
        btnPause.Text = "暂停(&P)"
        Num2.Enabled = True
        btnSend.Enabled = True
        btnPause.Enabled = True
        btnKill.Enabled = True
    End Sub
    Private Sub ShowLabel1(ByVal i As Integer)
        If (i - 1 + WinSize > 20) Then
            Label1.Width = POS_WIDTHW * (20 - i + 1)
        Else
            Label1.Width = POS_WIDTHW * WinSize
        End If
        Label1.Left = TopLabel(1).Left - (POS_WIDTHW - POS_WIDTH) / 2 + POS_WIDTHW * (i - 1)
        Label1.Top = POS_TOP - 2
        Label1.Height = TopLabel(1).Height + 4
    End Sub

    Private Sub ShowLabel2(ByVal i As Integer)
        If (i - 1 + WinsizeR > 20) Then
            Label2.Width = POS_WIDTHW * (20 - i + 1)
        Else
            Label2.Width = POS_WIDTHW * WinsizeR
        End If
        Label2.Left = TopLabel(1).Left - (POS_WIDTHW - POS_WIDTH) / 2 + POS_WIDTHW * (i - 1)
        Label2.Top = POS_BOTT - 2
        Label2.Height = TopLabel(1).Height + 4
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnPause.Click
        If tmr_Global.Enabled = False Then
            tmr_Global.Enabled = True
            btnPause.Text = "暂停(&P)"
        Else
            tmr_Global.Enabled = False
            btnPause.Text = "继续(&C)"
        End If
    End Sub

    Private Sub btnSend_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSend.Click
        Dim i As Integer
        Num2.Enabled = False
        For i = 1 To WinSize
            If (TXWin + i - 1 > 20) Then Exit For
            If (Pkg_Dir(TXWin + i - 1) <> 0 Or Pkg_RcvT(TXWin + i - 1) = 1 Or Tmr_Cnt(TXWin + i - 1) > 0) Then
            Else
                PkgLabel(TXWin + i - 1).Visible = True
                Pkg_Sent(TXWin + i - 1) = 1
                Pkg_Dir(TXWin + i - 1) = 1
                Tmr_Cnt(TXWin + i - 1) = TMR_MAX
                Exit For
            End If
        Next
    End Sub

    Private Sub btnKill_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnKill.Click
        Dim i As Integer
        For i = 1 To 20
            If (PkgLabel(i).BackColor = Color.Cyan) Then
                Pkg_Dir(i) = 0
                PkgLabel(i).Visible = False
                PkgLabel(i).Top = POS_TOP
                PkgLabel(i).BackColor = Color.Red
            End If
        Next

    End Sub

    Private Sub btnReset_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnReset.Click
        Reset_All()
    End Sub

    Private Sub Num1_ValueChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Num1.ValueChanged
        If (Num1.Value > 5) Then Num1.Value = 5
        If (Num1.Value < 1) Then Num1.Value = 1
        WinSize = Num1.Value
        'ShowLabel1(1)
    End Sub

    Private Sub Num2_ValueChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles Num2.ValueChanged
        If (Num2.Value > 5) Then Num2.Value = 5
        If (Num2.Value < 1) Then Num2.Value = 1
        WinsizeR = Num2.Value
    End Sub
End Class