HTTP协议是文本格式通讯，下载文件是二进制数据，怎样处理好两种格式，而不受VB独断专行的Unicode转换影响，本代码提供了一个示例。
Option Explicit
Private strURL As String
Private mstrFileName As String, mlngFileNum As Long
Private mlngFileLen As Long, mlngCurByte As Long
Private mblnOnlyLen As Boolean, mblnPutStart As Boolean
Private Sub Form_Load()
strURL = Text1.Text '准备下载的文件URL
mstrFileName = Text2.Text '下载文件在本存放的位置与文件名
Label1.Caption = '文件总字节:0'
Label2.Caption = '已下载字节:0'
Command1.Caption = '开始下载'
Command2.Caption = '取得长度'
End Sub
Private Sub Command1_Click()
mblnOnlyLen = False
DownFile
End Sub
Private Sub Command2_Click()
mblnOnlyLen = True
Label1.Caption = '文件总字节:0'
DownFile
End Sub
Private Sub DownFile()
mblnPutStart = False
Label2.Caption = '已下载字节:0'
Command1.Enabled = False
Command2.Enabled = False
With Winsock1
If .State <> sckClosed Then .Close
.Protocol = sckTCPProtocol
.RemoteHost = 'article.tianyaclub.com'
.RemotePort = 80
.Connect
End With
End Sub
Private Sub Winsock1_Connect()
Dim s As String
s = 'GET ' + strURL + ' HTTP/1.0' + vbCrLf
s = s + 'Accept: */*' + vbCrLf
s = s & 'Pragma: no-cache' & vbCrLf
s = s & 'Cache-Control: no-cache' & vbCrLf
s = s & 'Connection: close' & vbCrLf & vbCrLf
s = s + vbCrLf
Winsock1.SendData s
End Sub
Private Sub CloseAll()
If Winsock1.State <> sckClosed Then Winsock1.Close
Close #mlngFileNum
Command1.Enabled = True
Command2.Enabled = True
End Sub
Private Sub Winsock1_DataArrival(ByVal bytesTotal As Long)
Dim RevData() As Byte
Dim a() As Byte, b() As String, c() As String
Dim s As String, i As Long, k As Long
On Error GoTo fail
If mblnPutStart = False Then
Winsock1.PeekData RevData, vbArray Or vbByte
k = InStrB(1, RevData, ChrB(13) & ChrB(10) & ChrB(13) & ChrB(10))
If k > 0 Then
Winsock1.GetData RevData, vbArray Or vbByte
a = LeftB(RevData, k - 1)
RevData = MidB(RevData, k + 4)
s = StrConv(a, vbUnicode)
b = Split(s, vbCrLf)
If InStr(1, b(0), '200 OK', vbTextCompare) = 0 Then GoTo fail
For i = 1 To UBound(b)
c = Split(b(i), ': ')
Select Case c(0)
Case 'Content-Length'
mlngFileLen = CLng(c(1))
Label1.Caption = '文件总字节:' & mlngFileLen
If mblnOnlyLen Then
CloseAll
Exit Sub
End If
End Select
Next
mblnPutStart = True
mlngCurByte = UBound(RevData) + 1
mlngFileNum = FreeFile
Open mstrFileName For Binary As #mlngFileNum
Else
Exit Sub
End If
Else
Winsock1.GetData RevData, vbArray Or vbByte
mlngCurByte = mlngCurByte + bytesTotal
End If
Put #mlngFileNum, , RevData
Label2.Caption = '已下载字节:' & mlngCurByte
If mlngCurByte = mlngFileLen Then
CloseAll
MsgBox '下载成功！'
End If
Exit Sub
fail:
CloseAll
MsgBox '网络传输错误，文件下载失败！'
End Sub
