Need Help On Restarting Threads

  • Thread starter Thread starter pbd22
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pbd22

Hi.

I am getting the error: "Thread is running or terminated. It cannot
restart." It is happening inside a file upload loop where
a thread is created for each file (reporting bytes). After the first
file is uploaded, the error is thrown at workThread.Start().

I am new to threading and would appreciate advice on how to code this
so when the next file is starting to upload, the thread is restarted
(reinstantiated).

Below is a little on the function and the code:

---------------------------------------------------------

I have a function SendVideo().

Inside the function I have a thread that counts bytes:

Code:

Dim workThread As New Thread(New ThreadStart(AddressOf ftp.doWork))



Further down, I have a loop that starts the thread before the
upload begins and calls join after each upload:

Code:

For iFile = 0 To myfiles.Count - 1

workThread.Start()
ftp.UploadFile(postedFile.FileName)
workThread.Join()
End If

Next iFile



workThread.Start() above is where the error is thrown after the first
upload.

Thanks....
 
pbd22 said:
I am getting the error: "Thread is running or terminated. It cannot
restart." It is happening inside a file upload loop where
a thread is created for each file (reporting bytes). After the first
file is uploaded, the error is thrown at workThread.Start().
Click to expand...
Dim workThread As New Thread(New ThreadStart(AddressOf ftp.doWork))
Click to expand...
For iFile = 0 To myfiles.Count - 1

workThread.Start()
ftp.UploadFile(postedFile.FileName)
workThread.Join()
End If

Next iFile

workThread.Start() above is where the error is thrown after the first
upload.
Click to expand...
<snip>

As the error says, the thread has already run, it seems you can't
'restart' it. I guess you'll have to recreate the thread at each
cicle.

Anyway, it seems that there are other issues with your code. I
couldn't identify the class you're using as "ftp", but it seems that
you're starting the thread to "doWork" while also commanding the ftp
object to "UploadFile". This seems a bit confusing: which one is
actually performing the download? Maybe you could post more
information about the kind of classes you're using.

Regards,

Branco.
 
<snip>

As the error says, the thread has already run, it seems you can't
'restart' it. I guess you'll have to recreate the thread at each
cicle.

Anyway, it seems that there are other issues with your code. I
couldn't identify the class you're using as "ftp", but it seems that
you're starting the thread to "doWork" while also commanding the ftp
object to "UploadFile". This seems a bit confusing: which one is
actually performing the download? Maybe you could post more
information about the kind of classes you're using.

Regards,

Branco.
Click to expand...


Thanks for your reply Branco.

The ftp class is the MSDN-provided class for uploading files to a
remote server.
I'll spare you the massive code dump, but if you want to check it out,
its called
clsFTP and it is here: http://www.dotnethero.com/hero/vbnet/ftp.aspx?nmx=8_4
I have instantiated it for local file access as: Dim ftp As New clsFTP

I have made some changes to clsFTP so I can count bytes as files are
uploaded.
Namely, I have added the following event handler:

Delegate Sub IncrementEventHandler(ByVal sender As Object, ByVal e As
IncrementEventArgs)

-- and --

Public Event Incremented As IncrementEventHandler

The event handler gets fired every time the amount of bytes are
incremented during the upload. I have made this change in the
UploadFile method 2/3rds the way down clsFTP:

Do While (m_iBytes > 0)

cSocket.Send(m_aBuffer, m_iBytes, 0)
m_iBytes = input.Read(m_aBuffer, 0,
m_aBuffer.Length)

m_iBytesTotal += m_iBytes

doWork() // THIS METHOD FIRES THE EVENT HANDLER

Loop

Public Sub doWork()
RaiseEvent Incremented(Me, New
IncrementEventArgs(m_iBytesTotal))
End Sub

Finally, I have a method, SendVideo(), in a different file that gets
called once the queue of videos starts to upload. As each video is
uploaded the workThread keeps count of the bytes being uploaded to
show progress. As mentioned, after the first video is uploaded (which
succeeds) the error is thrown when the second one starts to upload.
Here is a bit more of that method:

Public Sub SendVideo()

Dim ftp As New clsFTP
Dim myfiles As HttpFileCollection

Dim workThread As New Thread(New ThreadStart(AddressOf
ftp.doWork))

myfiles = HttpContext.Current.Request.Files

' subscribe a delegate with the event
AddHandler ftp.Incremented, AddressOf onIncrement

If (ftp.Login() = True) Then

Dim iFile As Integer

For iFile = 0 To myfiles.Count - 1

Dim postedFile As HttpPostedFile = myfiles(iFile)
filesize = postedFile.InputStream.Length

If Not postedFile.FileName.Equals("") Then

workThread.Start()
ftp.UploadFile(postedFile.FileName)
workThread.Join()
End If
Next iFile

ftp.CloseConnection()

End If

[ETC...]

Per a discussion with a friend, I am told that this is a classic
Producer/Consumer situation in multithreading. If you agree with this
(or have another suggestion), I would appreciate it if you could
provide code examples in addition to conceptual advice as it helps me
understand what is going on. Of course, if you need more information,
please let me know.

Thanks in advance for your attention.
Peter
 
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