局域网文件传输软件[通俗易懂]

大家好，又见面了，我是你们的朋友全栈君。在公司实习了一个周，虽然很累，但也感觉有所得，此次项目是做一个局域网两台计算机之间的文件传输。我用的主要控件为winsock控件，用其TCP协议。至于用此控件连接两台计算机书上都有介绍，我主要介绍一下我传送文件的思想和方法：

首先，将要传送的文件分成指定大小的N个包，大小不能超过8K因为TCP每次最多发送8K数据，最后一个包可能会小于其它包。然后在每个包加个包头，因为接收端需要通过包头知道传送过来的是数据还是路径（因为发送端指定存放路径），接收端收到数据后必须返回确认到发送端，这样才能循环发送，但一定要有最后的终止，不然会死循环。我的主要发送和接收代码如下：

发送端收到数据后产生的事件

Private Sub WskCli_DataArrival(ByVal bytesTotal As Long)

    Dim FIT As Boolean, OVER As Boolean, xx As Byte

    WskCli.GetData FIT

    If Number < BagNum Then

        If FIT = True Then ‘接收端已收到上一个数据包

           

            If v <> 0 Then ‘传送速率受限制

                Dim ss As Long

                ss = 0

                Do Until (Number * 1024 <= v * ss) ‘传送速率过大则等待

                    ss = CLng((Time – timeInt) * 3600 * 24)

                Loop

            End If

           

            Send_File ‘调用发送文件数据包过程

        End If

        Number = Number + 1 ‘计数

        ProgressBar1.Value = Number * 20 / BagNum ‘刷新进度条的进度

    El**

        *x = 2

        WskCli.SendData xx ‘发送传送完毕的信息给接收端

        Close 1

        Label1.Caption = “发送完毕！”

        OVER = True

        Number = 0 ‘传送完后置计数Number=0

    End If

    If OVER = True Then ‘传送完之后的处理

        Drive1.Enabled = True

        Dir1.Enabled = True

        File1.Enabled = True

        CmdSend.Enabled = True

        Exit Sub

    End If

End Sub

send_file是自定义的一个发送过程:

Private Sub Send_File()

    Dim i As Long ‘循环变量

    If Number <= BagNum – 1 Then

        ReDim Buff(1 To BagSize) As Byte ‘定义缓冲区

        ReDim TempBuff(0 To BagSize) As Byte

       

        Get 1, , Buff

       

        TempBuff(0) = 1 ‘设置包头为1代表文件数据

        For i = 1 To BagSize

            TempBuff(i) = Buff(i)

        Next

       

        WskCli.SendData TempBuff

    Else

        ‘传送最后一个数据包

        n = filelength – Seek(1) + 1 ‘得到最后一个包的大小

        If n > 0 Then

            ReDim Buff(0 To n) As Byte

            ReDim TempBuff(0 To n) As Byte

            TempBuff(0) = 1 ‘设置包头为1代表文件数据

            Get 1, , Buff

            For i = 1 To n

                TempBuff(i) = Buff(i – 1)

            Next

            WskCli.SendData TempBuff

        End If

    End If

End Sub

‘发送按钮被按下的响应事件

Private Sub CmdSend_Click()

    CmdSend.Enabled = False

    Combo1.Enabled = False

    If Combo1.Text = “” Then

        MsgBox “请选择一个传输速度！”, vbOKOnly, “错误”

    Else

        ‘传送速度的选择

        Select Case Combo1.ListIndex

            Case 0

                v = CLng(200) * 1024

            Case 1

                v = CLng(600) * 1024

            Case 2

                v = 1.5 * CLng(1024) * 1024

            Case 3

                v = 2 * CLng(1024) * 1024

            Case 4

                v = 0

        End Select

        If Number > 0 Then

            ‘重传或续传

            If MsgBox(“上次未能传送完成，是否续传？”, vbYesNo, “提示”) = vbNo Then Number = 0: Close 1

        End If

       

        ReDim Buff(Len(sendFileName)) As Byte

        Buff(0) = 0

        For i = 1 To Len(sendFileName)

            Buff(i) = Asc(Mid(sendFileName, i, 1))

        Next

        WskCli.SendData Buff ‘发送文件路径和文件名

    End If

    Open fn For Binary Access Read As #1

   

    ‘设置数据包的数量

    filelength = LOF(1) ‘文件长度

    BagNum = filelength / BagSize

    If BagNum < filelength / BagSize Then BagNum = BagNum + 1

   

    ‘计时初始化

    timeInt = Time

End Sub

接收端接收数据的事件：

Private Sub WskSer_DataArrival(ByVal bytesTotal As Long)

    Dim Buff() As Byte ‘定义接收数据缓冲区

    Dim OVER As Boolean ‘结束标记

   

    WskSer.GetData Buff ‘接收数据

   

    ‘判断包头信息

    Select Case Buff(0) ‘包头

        Case 0

            ‘得到存放路径和文件名

            fn = “”

            For i = 1 To UBound(Buff)

                fn = fn + Chr(Buff(i))

            Next

           

            Open fn For Binary As #1 ‘新建或打开文件

            Close 1

            Label1.Caption = “正在发送”

        Case 1

            ‘写入文件

            Open fn For Binary Access Write As #1

            Seek #1, LOF(1) + 1 ‘找到文件尾

            ReDim TempBuff(1 To UBound(Buff)) As Byte

           

            ‘去掉包头

            For i = 1 To UBound(Buff)

                TempBuff(i) = Buff(i)

            Next

           

            Put 1, , TempBuff ‘将数据写入文件

            Close 1

        Case 2

            ‘接收结束

            Label1.Caption = “发送完毕！”

            OVER = True

    End Select

   

    If OVER = True Then Exit Sub ‘如果接收完毕则退出此过程

    WskSer.SendData True ‘告诉客户端继续发送下一个数据包

End Sub