Asp.net resumable upload

Resumable upload. The disadvantage is that the file name must be manually managed and cannot be repeated.
<%
Url = "http: // 127.0.0.1/test/20021317173156951.swf" 'address for testing
If url = "" Then die ("URL cannot be blank.") 'dare to repeat me, empty URL can't'
T = faster Rev (URL, "/") 'Get the last "/" location'
If T = 0 or T = Len (URL) Then die ("cannot get file name.") 'No "/" or end'
Filename = right (URL, Len (URL)-T) 'get the file name to be saved'
If not left (URL, 7) = "http: //" then url = "http: //" & url ", if you forget" http: // "carelessly, add'
Filename = server. mappath (filename)
Set FSO = server. Createobject ("scripting. FileSystemObject") 'fso, Aso, and HTTP. Each object must be unique'
Set Aso = server. Createobject ("ADODB. Stream ")
Set HTTP = server. Createobject ("Microsoft. XMLHTTP ")

If FSO. fileexists (filename) Then 'determine whether the object to be downloaded already exists'
Start = FSO. GetFile (filename). Size 'exists, with the current file size as the starting position'
Else
Start = 0 'nonexistent, everything starts from scratch'
FSO. createtextfile (filename). Close 'create file'
End if

Response. Write "connectting ..."
Response. Flush 'first play'
Current = start' current position is the start position
Do
HTTP. Open "get", URL, and false' HTTP is called in synchronous mode. I wanted to use asynchronous mode, but it has never been successful.
HTTP. setRequestHeader "range", "bytes =" & start & "-" & CSTR (start + 20480) 'here is the secret of resumable upload.
HTTP. setRequestHeader "Content-Type:", "application/octet-stream"
HTTP. Send' start sending after data packets are constructed'
For I = 1 to 60 'cyclic waiting'
If HTTP. readystate = 3 then showplan () 'status 3 indicates that the data is received and the progress is displayed'
If HTTP. readystate = 4 then exit for 'status 4 indicates the data is accepted successfully'
Sleep (1) 'Here is the latency. The square method is not very good.
Next
If not HTTP. readystate = 4 then die ("time-out.") '20 K is not finished in 1 minute? Timeout! '
If HTTP. Status> 299 then die ("error:" & HTTP. Status & "& HTTP. statustext) 'Isn't it, and an error occurs again? '
If not HTTP. Status = 206 then die ("the server does not support resumable upload.") 'the server does not support resumable upload'

Aso. type = 1 'data stream type set to byte'
Aso. Open
Aso. loadfromfile filename 'open file'
Aso. Position = start 'set the initial position of the file pointer'
Aso. Write HTTP. responsebody 'write Data'
Aso. savetofile filename, 2 'overwrite'
Aso. Close

Range = http. getResponseHeader ("content-range") 'Get "content-range"' in the HTTP Header "'
If range = "" Then die ("no.") 'You don't know if the download is complete'
Temp = mid (range, instr (range, "-") + 1) 'content-range is similar to 123-456/789'
Current = clng (left (temp, instr (temp, "/")-1) '2014 is the start position and 123 is the end position'
Total = clng (mid (temp, instr (temp, "/") + 1) '100 is the total number of bytes of the file'
If total-current = 1 then exit do 'the end position is 1 less than the total size, indicating that the transfer is completed'
Start = start + 20480 'otherwise download 20 k'
Loop while true

Response. Write CHR (13) & "downloaded (" & total & ")." 'downloaded, total Byte Count'

Function die (MSG) 'function name comes from Perl built-in function die'
Response. Write MSG 'last words ^_^'
Response. End 'Go to see Marx'
End Function

Function showplan () 'display download progress'
If I mod 3 = 0 then c = "/" 'simple dynamic Effect'
If I mod 3 = 1 then c = "-"
If I mod 3 = 2 then c = "\"
Response. Write CHR (13) & "download (" ¤ T & ")" & C & CHR (8) '13' ASCII code is returned to the beginning of the line, and 8'
Response. Flush
End Function

Sub sleep (delaytime)
Dim T1, T2, T3, CT, lt
T1 = hour (time) * 3600
T2 = minute (time) * 60
T3 = second (time)
// Converts the hour and minute of the current time into seconds and stores them in CT
Ct = t1 + T2 + T3
// Loop wait
Do
T1 = hour (time) * 3600
T2 = minute (time) * 60
T3 = second (time)
Lt = t1 + T2 + T3
Loop while (LT-CT <delaytime)
End sub
%>