vb.net winforms download without blocking - vb.net

I'm downloading files .mp3 and my goal is not to have even a minimum GUI freezing during downloading.
My aim is also to display the bites received in a progress bar and through labels.
This code is working, but sometimes is freezing without any reason, sometimes the progress bar doesn't work until file is completely done.
So far, this is the "best" code I found online for a completely working progress bar during a download, but still gets problems.
How do you think I can increase performances? How can I make a resistant and reliable working progressbar? How can I download also large file without GUI freezing? I tried (curiosity) to download a 600 mb file and it completely freeze, not responding and not giving any issue back.
Thanks
EDIT1: I'm trying with this,eventhough I'm lost on high waves.. Any idea on how can I use this code and insert it into Jimi Answer? Answer
Imports System.IO
Imports System.IO.Path
Imports System.Net
Public Class Form1
Private downloader As MyDownloader = Nothing
Private Sub btnStartDownload_Click(sender As Object, e As EventArgs) Handles btnStartDownload.Click
Dim progress = New Progress(Of String)(
Sub(data)
MsgBox("we are on the UI thread here")
End Sub)
Dim url As Uri = New Uri(TextBox1.Text)
downloader = New MyDownloader()
'How can I remove this second? I don't need download from url every 1 second.
downloader.StartDownload(progress, url, 1)
End Sub
And
Imports System.ComponentModel
Imports System.Diagnostics
Imports System.Net
Imports System.Net.Http
Imports System.Text.RegularExpressions
Imports System.Threading
Public Class MyDownloader
Private Shared ReadOnly client As New HttpClient()
client.DownloadProgressChanged += AddressOf Client_DownloadProgressChanged
client.DownloadFileCompleted += AddressOf Client_DownloadFileCompleted
Private interval As Integer = 0
Private Sub Client_DownloadFileCompleted(ByVal sender As Object, ByVal e As AsyncCompletedEventArgs)
System.Windows.Forms.MessageBox.Show("Download OK!", "Message", MessageBoxButtons.OK, MessageBoxIcon.Information)
End Sub
Public Sub StartDownload(progress As IProgress(Of String), url As Uri, intervalSeconds As Integer)
interval = intervalSeconds * 1000
Task.Run(Function() DownloadAsync(progress, url))
End Sub
Private Sub Client_DownloadProgressChanged(ByVal sender As Object, ByVal e As DownloadProgressChangedEventArgs)
ProgressBar1.Minimum = 0
Dim receive As Double = Double.Parse(e.BytesReceived.ToString())
Dim total As Double = Double.Parse(e.TotalBytesToReceive.ToString())
Dim percentage As Double = receive / total * 100
label2.Text = $"{String.Format("{0:0.##}", percentage)}%"
ProgressBar1.Value = Integer.Parse(Math.Truncate(percentage).ToString())
End Sub
Private Async Function DownloadAsync(progress As IProgress(Of String), url As Uri) As Task
Dim pattern As String = "<(?:[^>=]|='[^']*'|=""[^""]*""|=[^'""][^\s>]*)*>"
Dim downloadTimeWatch As Stopwatch = New Stopwatch()
downloadTimeWatch.Start()
Do
Try
Dim response = Await client.GetAsync(url, HttpCompletionOption.ResponseContentRead)
Dim data = Await response.Content.ReadAsStringAsync()
data = WebUtility.HtmlDecode(Regex.Replace(data, pattern, ""))
progress.Report(data)
Dim delay = interval - CInt(downloadTimeWatch.ElapsedMilliseconds)
Await Task.Delay(If(delay <= 0, 10, delay))
downloadTimeWatch.Restart()
Catch ex As Exception
End Try
Loop
End Function
End Class
I'm Seriously lost on it, I tried to delete cancel download as I am not going to stop any download and I tried also to delete Download from url every 1 second as I just need one time download for every link.
Thanks

Related

How to speed up Binance coin price parsing?

I'm trying to create a bot that place multiples orders on Binance and I need a fast coin price parsing.
I'm parsing the code using this code
Dim price as decimal
Private Async Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
Timer1.Stop()
Dim downloadTasks As New List(Of Task(Of String))
Dim dogebusd = wc1.DownloadStringTaskAsync("https://api.binance.com/api/v1/ticker/price?symbol=DOGEBUSD")
downloadTasks.Add(dogebusd)
Await Task.WhenAll(downloadTasks)
Dim d = JsonConvert.DeserializeObject(Of Dictionary(Of String, String))(dogebusd.Result)
Dim PREZZO As Decimal = CDec(Val((d("price")).ToString))
price = CDec((PREZZO))
Timer1.Start()
End Sub
but when the price is dumping or pumping really fast, even a 10 ms or 100ms timer tick is not that efficient.
I wonder if this is the fastest way possible or if I can improve the code.
Thanks
following Jimi suggestions:
Dim price As Decimal
Private ReadOnly _timer As New PeriodicTimer(TimeSpan.FromSeconds(1))
Private Async Sub Timer1_Tick(sender As Object, e As EventArgs) Handles _timer.Tick
timer1.stop
Dim dogebusdTask = HttpClient.GetStringAsync("https://api.binance.com/api/v1/ticker/price?symbol=DOGEBUSD")
Await dogebusdTask
Dim d = JsonConvert.DeserializeObject(Of Dictionary(Of String, String))(dogebusdTask.Result)
If Decimal.TryParse(d("price"), NumberStyles.Number, CultureInfo.InvariantCulture, price) Then
_timer.Start()
End If
End Sub
An example, using the .NET 6+ awaitable PeriodicTimer and System.Text.Json to parse the resulting stream returned by HttpClient's GetStreamAsync()
The PeriodicTimer can be quite efficient in contexts like this, since it tries to keep up with the interval you have provided. Since the internal procedure takes time to execute - the HttpClient.GetStreamAsync() takes an undetermined amount of time to execute and return a result - the Timer keeps track of the actual elapsed time and tries to keep ticking steadily (unless the procedure takes more than the specified Interval, then you skip a beat, of course)
Note: as usual, when dealing with Tasks that accept a CancellationToken, you should run this code without a Debugger (CTRL+F5) or configure the Debugger to not halt on TaskCanceledException or OperationCanceledException, otherwise it handles the (ignorable) exception before you do
Imports System.Globalization
Imports System.Net.Http
Imports System.Text.Json
Imports System.Threading
Private Shared ReadOnly m_Client As New HttpClient()
Private timerCts As CancellationTokenSource = Nothing
Private m_PeriodicTimer As PeriodicTimer = Nothing
Private m_PeriodicTimerInterval As Integer = 500
Private currentPrice As Decimal = 0.0D
Private Async Function StartPriceLookupTimer(token As CancellationToken, timerInterval As Integer) As Task
If token.IsCancellationRequested Then Return
Dim lookupAddress = "https://api.binance.com/api/v1/ticker/price?symbol=DOGEBUSD"
m_PeriodicTimer = New PeriodicTimer(TimeSpan.FromMilliseconds(timerInterval))
Try
While Await m_PeriodicTimer.WaitForNextTickAsync(token)
Dim jsonStream = Await m_Client.GetStreamAsync(lookupAddress, token)
Try
Dim prop = (Await JsonDocument.ParseAsync(jsonStream, Nothing, token)).RootElement.GetProperty("price")
Dim strPrice = prop.GetString()
If Decimal.TryParse(strPrice, CultureInfo.InvariantCulture, currentPrice) Then
' Do whatever you need to do with the parsed value
' E.g., assign it to a TextBox for presentation,
' using the current Culture format, since strPrice contains the original format
[Some TextBox].Text = currentPrice.ToString() ' <= UI Thread here
End If
Catch knfex As KeyNotFoundException
Debug.WriteLine("The JSON property was not found")
Catch tcex As TaskCanceledException
Debug.WriteLine("The lookup procedure was canceled")
End Try
End While
Catch tcex As TaskCanceledException
Debug.WriteLine("The lookup procedure was canceled")
End Try
End Function
Private Sub StopPriceLookupTimer()
timerCts?.Cancel()
m_PeriodicTimer?.Dispose()
timerCts?.Dispose()
timerCts = Nothing
End Sub
How to start this lookup procedure, calling the StartPriceLookupTimer() method?
You could use a Button, making its Click handler async:
Private Async Sub SomeButton_Click(sender As Object, e As EventArgs) Handles SomeButton.Click
If timerCts Is Nothing Then
timerCts = New CancellationTokenSource()
Await StartPriceLookupTimer(timerCts.Token, m_PeriodicTimerInterval)
Else
Debug.WriteLine("Lookup Timer already started")
End If
End Sub
Or make the Form's Shown Handler / OnShown() method override async and start the procedure when the Form is first presented:
Protected Overrides Async Sub OnShown(e As EventArgs)
MyBase.OnShown(e)
timerCts = New CancellationTokenSource()
Await StartPriceLookupTimer(timerCts.Token, m_PeriodicTimerInterval)
End Sub
To stop the lookup procedure, call the StopPriceLookupTimer() method when needed, e.g., using another Button or in the Form.Closed handler / OnFormClosed() override

Object reference not set to an instance of object - vb.net

First a little background information: The purpose of this application is to capture images and save them automatically to a network directory that will be either created or appended using the input of the text box. This code DOES work on my computer (windows 7 home 64 bit). I've created it using microsoft visual basic express 2010.
However..... when attempting to run the application on a windows 10 tablet, I get the follow errors:
On form load:
An error occurred while capturing the image. The video capture will now be terminated.
Object reference not set to an instance of an object.
On button2_Click Event:
Object reference not set to an instance of an object.
Below is the entirety of the code.
Form2.vb
Public Class Form2
Public scanIsSet As Boolean
Private webcam As WebCam
Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
webcam = New WebCam()
webcam.InitializeWebCam(imgVideo)
webcam.Start()
scanIsSet = False
End Sub
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Dim CFGfile As String
Dim SaveDir As String
Dim imgIndex As Integer
Dim existingImages() As String
SaveDir = "C:\somepath\"
'save image to directory with index number
Try
imgCapture.Image.Save(SaveDir & OrderNumber.Text & "\" & CStr(imgIndex) & ".jpg")
Catch ex As Exception
MsgBox("error while accessing object imgCapture" & ex.Message)
End Try
imgIndex = imgIndex + 1
Else
Beep()
MsgBox("Please scan or type in order number first")
End If
End Sub
End Class
WebCam.vb
Imports System
Imports System.IO
Imports System.Linq
Imports System.Text
Imports WebCam_Capture
Imports System.Collections.Generic
Imports ZXing
Imports ZXing.OneD
'Design by Pongsakorn Poosankam
Class WebCam
Public scanz As Boolean
Public Sub setScan(ByVal x As Boolean)
scanz = x
End Sub
Private webcam As WebCamCapture
Private _FrameImage As System.Windows.Forms.PictureBox
Private FrameNumber As Integer = 30
Public Sub InitializeWebCam(ByRef ImageControl As System.Windows.Forms.PictureBox)
webcam = New WebCamCapture()
webcam.FrameNumber = CULng((0))
webcam.TimeToCapture_milliseconds = FrameNumber
AddHandler webcam.ImageCaptured, AddressOf webcam_ImageCaptured
_FrameImage = ImageControl
End Sub
Private Sub webcam_ImageCaptured(ByVal source As Object, ByVal e As WebcamEventArgs)
_FrameImage.Image = e.WebCamImage
If scanz = True Then
Dim BCreader As New ZXing.BarcodeReader
'BCreader.Options.TryHarder = True
Try
Dim resu As Result = BCreader.Decode(e.WebCamImage)
Form2.OrderNumber.Text = resu.Text
setScan(False)
Form2.Label2.Text = ""
Beep()
Catch ex As Exception
'do nothing
End Try
End If
End Sub
Public Sub Start()
webcam.TimeToCapture_milliseconds = FrameNumber
webcam.Start(0)
End Sub
Public Sub [Stop]()
webcam.[Stop]()
End Sub
Public Sub [Continue]()
' change the capture time frame
webcam.TimeToCapture_milliseconds = FrameNumber
' resume the video capture from the stop
webcam.Start(Me.webcam.FrameNumber)
End Sub
Public Sub ResolutionSetting()
webcam.Config()
End Sub
Public Sub AdvanceSetting()
webcam.Config2()
End Sub
End Class
As you can see toward the end of Form2.vb, I've wrapped imgCapture.Image.Save(SaveDir & OrderNumber.Text & "\" & CStr(imgIndex) & ".jpg") in a Try-Catch block because I suspect it's some sort of problems with the pictureBox objects. The try catch block does indeed catch the exception, but I still have no idea what the problem is, why it happens on the tablet and not the PC, or how to fix it.
I've found similar questions, but none with a solution I can make use of.
Since you are using a library, EasyWebCam, that is outdated and not compatible with Win10, I would suggest switching libraries. Other options out there:
DirectX.Capture
Windows.Media.Capture
I FOUND THE SOLUTION BUT I DON'T KNOW IF YOU NEED IT NOW ANYWAY THE PROBLEM IS IF YOU HAVE CHANGED THE PICTUREBOX NAME THEN IN REFENCES USE THE EXACT NAME YOU HAVE CHANGED TO. EXAMPLE IF I CHANGE ALL MY PICTUREBOX NAMES AS -
PictureBox_A1 , PictureBox_A2 ,... and so on then my refence should be as -
Dim r As DataRow
For Each r In t1.Rows
CType(Controls("PictureBox_" & r(2)), PictureBox).Image = bookedicon
Next
MY REFERENCE IS - "PictureBox_"

Is there away to switch from a Worker Thread to the Main (UI) thread?

I apologize in advance if my question is too long-winded. I looked at the question “How to update data in GUI with messages that are being received by a thread of another class?” and it is very close to what I am trying to do but the answer was not detailed enough to be helpful.
I have converted a VB6 app to VB.NET (VS2013). The main function of the app is to send queries to a Linux server and display the results on the calling form. Since the WinSock control no longer exists, I’ve created a class to handle the functions associated with the TcpClient class. I can successfully connect to the server and send and receive data.
The problem is that I have multiple forms that use this class to send query messages to the server. The server responds with data to be displayed on the calling form. When I try to update a control on a form, I get the error "Cross-thread operation not valid: Control x accessed from a thread other than the thread it was created on." I know I’m supposed to use Control.InvokeRequired along with Control.Invoke in order to update controls on the Main/UI thread, but I can’t find a good, complete example in VB. Also, I have over 50 forms with a variety of controls on each form, I really don’t want to write a delegate handler for each control. I should also mention that the concept of threads and delegates is very new to me. I have been reading everything I can find on this subject for the past week or two, but I’m still stuck!
Is there some way to just switch back to the Main Thread? If not, is there a way I can use Control.Invoke just once to cover a multitude of controls?
I tried starting a thread just after connecting before I start sending and receiving data, but netStream.BeginRead starts its own thread once the callback function fires. I also tried using Read instead of BeginRead. It did not work well if there was a large amount of data in the response, BeginRead handled things better. I feel like Dorothy stuck in Oz, I just want to get home to the main thread!
Thanks in advance for any help you can provide.
Option Explicit On
Imports System.Net
Imports System.Net.Sockets
Imports System.Text
Imports System.Threading
Friend Class ATISTcpClient
Public Event Receive(ByVal data As String)
Private Shared WithEvents oRlogin As TcpClient
Private netStream As NetworkStream
Private BUFFER_SIZE As Integer = 8192
Private DataBuffer(BUFFER_SIZE) As Byte
Public Sub Connect()
Try
oRlogin = New Net.Sockets.TcpClient
Dim localIP As IPAddress = IPAddress.Parse(myIPAddress)
Dim localPrt As Int16 = myLocalPort
Dim ipLocalEndPoint As New IPEndPoint(localIP, localPrt)
oRlogin = New TcpClient(ipLocalEndPoint)
oRlogin.NoDelay = True
oRlogin.Connect(RemoteHost, RemotePort)
Catch e As ArgumentNullException
Debug.Print("ArgumentNullException: {0}", e)
Catch e As Net.Sockets.SocketException
Debug.Print("SocketException: {0}", e)
End Try
If oRlogin.Connected() Then
netStream = oRlogin.GetStream
If netStream.CanRead Then
netStream.BeginRead(DataBuffer, 0, BUFFER_SIZE, _
AddressOf DataArrival, DataBuffer)
End If
Send(vbNullChar)
Send(User & vbNullChar)
Send(User & vbNullChar)
Send(Term & vbNullChar)
End If
End Sub
Public Sub Send(newData As String)
On Error GoTo send_err
If netStream.CanWrite Then
Dim sendBytes As [Byte]() = Encoding.UTF8.GetBytes(newData)
netStream.Write(sendBytes, 0, sendBytes.Length)
End If
Exit Sub
send_err:
Debug.Print("Error in Send: " & Err.Number & " " & Err.Description)
End Sub
Private Sub DataArrival(ByVal dr As IAsyncResult)
'This is where it switches to a WorkerThread. It never switches back!
On Error GoTo dataArrival_err
Dim myReadBuffer(BUFFER_SIZE) As Byte
Dim myData As String = ""
Dim numberOfBytesRead As Integer = 0
numberOfBytesRead = netStream.EndRead(dr)
myReadBuffer = DataBuffer
myData = myData & Encoding.ASCII.GetString(myReadBuffer, 0, numberOfBytesRead)
Do While netStream.DataAvailable
numberOfBytesRead = netStream.Read(myReadBuffer, 0, myReadBuffer.Length)
myData = myData & Encoding.ASCII.GetString(myReadBuffer, 0, numberOfBytesRead)
Loop
'Send data back to calling form
RaiseEvent Receive(myData)
'Start reading again in case we don‘t have the entire response yet
If netStream.CanRead Then
netStream.BeginRead(DataBuffer, 0,BUFFER_SIZE,AddressOf DataArrival,DataBuffer)
End If
Exit Sub
dataArrival_err:
Debug.Print("Error in DataArrival: " & err.Number & err.Description)
End Sub
Instead of using delegates one could use anonymous methods.
Singleline:
uicontrol.Window.Invoke(Sub() ...)
Multiline:
uicontrol.Window.Invoke(
Sub()
...
End Sub
)
If you don't want to pass an UI control every time you need to invoke, create a custom application startup object.
Friend NotInheritable Class Program
Private Sub New()
End Sub
Public Shared ReadOnly Property Window() As Form
Get
Return Program.m_window
End Get
End Property
<STAThread()> _
Friend Shared Sub Main()
Application.EnableVisualStyles()
Application.SetCompatibleTextRenderingDefault(False)
Dim window As New Form1()
Program.m_window = window
Application.Run(window)
End Sub
Private Shared m_window As Form
End Class
Now, you'll always have access to the main form of the UI thread.
Friend Class Test
Public Event Message(text As String)
Public Sub Run()
Program.Window.Invoke(Sub() RaiseEvent Message("Hello!"))
End Sub
End Class
In the following sample code, notice that the Asynchronous - Unsafe run will throw a Cross-thread exception.
Imports System.Threading
Imports System.Threading.Tasks
Public Class Form1
Public Sub New()
Me.InitializeComponent()
Me.cbOptions = New ComboBox() With {.TabIndex = 0, .Dock = DockStyle.Top, .DropDownStyle = ComboBoxStyle.DropDownList} : Me.cbOptions.Items.AddRange({"Asynchronous", "Synchronous"}) : Me.cbOptions.SelectedItem = "Asynchronous"
Me.btnRunSafe = New Button() With {.TabIndex = 1, .Dock = DockStyle.Top, .Text = "Run safe!", .Height = 30}
Me.btnRunUnsafe = New Button() With {.TabIndex = 2, .Dock = DockStyle.Top, .Text = "Run unsafe!", .Height = 30}
Me.tbOutput = New RichTextBox() With {.TabIndex = 3, .Dock = DockStyle.Fill}
Me.Controls.AddRange({Me.tbOutput, Me.btnRunUnsafe, Me.btnRunSafe, Me.cbOptions})
Me.testInstance = New Test()
End Sub
Private Sub _ButtonRunSafeClicked(s As Object, e As EventArgs) Handles btnRunSafe.Click
Dim mode As String = CStr(Me.cbOptions.SelectedItem)
If (mode = "Synchronous") Then
Me.testInstance.RunSafe(mode)
Else 'If (mode = "Asynchronous") Then
Task.Factory.StartNew(Sub() Me.testInstance.RunSafe(mode))
End If
End Sub
Private Sub _ButtonRunUnsafeClicked(s As Object, e As EventArgs) Handles btnRunUnsafe.Click
Dim mode As String = CStr(Me.cbOptions.SelectedItem)
If (mode = "Synchronous") Then
Me.testInstance.RunUnsafe(mode)
Else 'If (mode = "Asynchronous") Then
Task.Factory.StartNew(Sub() Me.testInstance.RunUnsafe(mode))
End If
End Sub
Private Sub TestMessageReceived(text As String) Handles testInstance.Message
Me.tbOutput.Text = (text & Environment.NewLine & Me.tbOutput.Text)
End Sub
Private WithEvents btnRunSafe As Button
Private WithEvents btnRunUnsafe As Button
Private WithEvents tbOutput As RichTextBox
Private WithEvents cbOptions As ComboBox
Private WithEvents testInstance As Test
Friend Class Test
Public Event Message(text As String)
Public Sub RunSafe(mode As String)
'Do some work:
Thread.Sleep(2000)
'Notify any listeners:
Program.Window.Invoke(Sub() RaiseEvent Message(String.Format("Safe ({0}) # {1}", mode, Date.Now)))
End Sub
Public Sub RunUnsafe(mode As String)
'Do some work:
Thread.Sleep(2000)
'Notify any listeners:
RaiseEvent Message(String.Format("Unsafe ({0}) # {1}", mode, Date.Now))
End Sub
End Class
End Class
Thank you to those who took the time to make suggestions. I found a solution. Though it may not be the preferred solution, it works beautifully. I simply added MSWINSCK.OCX to my toolbar, and use it as a COM/ActiveX component. The AxMSWinsockLib.AxWinsock control includes a DataArrival event, and it stays in the Main thread when the data arrives.
The most interesting thing is, if you right click on AxMSWinsockLib.DMSWinsockControlEvents_DataArrivalEvent and choose Go To Definition, the object browser shows the functions and delegate subs to handle the asynchronous read and the necessary delegates to handle BeginInvoke, EndInvoke, etc. It appears MicroSoft has already done the hard stuff that I did not have the time or experience to figure out on my own!

How can I properly implement threaded downloads using WebClient with a BlockingCollection?

I'm attempting to make a multi-threaded download manager that has a limit of 4 concurrent downloads. In my research, I came across the following: C# Downloader: should I use Threads, BackgroundWorker or ThreadPool?
[edit] updated code:
Imports System.Net
Imports System.Collections.Concurrent
Imports System.ComponentModel
Imports System.Threading
Public Class Form1
Const MaxClients As Integer = 4
' create a queue that allows the max items
Dim ClientQueue As New BlockingCollection(Of WebClient)(MaxClients)
' queue of urls to be downloaded (unbounded)
Dim UrlQueue As New Queue(Of String)()
Dim downloadThread As Thread
'Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
' create four WebClient instances and put them into the queue
For i As Integer = 0 To MaxClients - 1
Dim cli = New WebClient()
AddHandler cli.DownloadFileCompleted, AddressOf DownloadFileCompleted
AddHandler cli.DownloadProgressChanged, AddressOf DownloadProgressChanged
ClientQueue.Add(cli)
Next
' Fill the UrlQueue here
UrlQueue.Enqueue("http://www.gnu.org/licenses/gpl-1.0.txt")
UrlQueue.Enqueue("http://www.gnu.org/licenses/gpl-2.0.txt")
UrlQueue.Enqueue("http://www.gnu.org/licenses/gpl-3.0.txt")
UrlQueue.Enqueue("http://www.gnu.org/licenses/lgpl-2.1.txt")
UrlQueue.Enqueue("http://www.gnu.org/licenses/lgpl-3.0.txt")
UrlQueue.Enqueue("http://www.gnu.org/licenses/fdl-1.1.txt")
UrlQueue.Enqueue("http://www.gnu.org/licenses/fdl-1.2.txt")
UrlQueue.Enqueue("http://www.gnu.org/licenses/fdl-1.3.txt")
downloadThread = New Thread(AddressOf downloadQueue)
downloadThread.IsBackground = True
downloadThread.Start()
End Sub
Private Sub downloadQueue()
' Now go until the UrlQueue is empty
While UrlQueue.Count > 0
Dim cli As WebClient = ClientQueue.Take() ' blocks if there is no client available
Dim url As String = UrlQueue.Dequeue()
Dim fname As String = CreateOutputFilename(url)
cli.DownloadFileAsync(New Uri(url), fname, New DownloadArgs(url, fname, cli))
AppendText(url & " started" & vbCrLf)
End While
End Sub
Private Sub DownloadProgressChanged(sender As Object, e As DownloadProgressChangedEventArgs)
Dim args As DownloadArgs = DirectCast(e.UserState, DownloadArgs)
' Do status updates for this download
End Sub
Private Sub DownloadFileCompleted(sender As Object, e As AsyncCompletedEventArgs)
Dim args As DownloadArgs = DirectCast(e.UserState, DownloadArgs)
' do whatever UI updates
Dim url As String = "Filename" '<============I'd like to be able to pass the filename or URL but can't figure this out
AppendText(url & " completed" & vbCrLf)
' now put this client back into the queue
ClientQueue.Add(args.Client)
End Sub
Public Function CreateOutputFilename(ByVal url As String) As String
Try
Return url.Substring(url.LastIndexOf("/") + 1)
Catch ex As Exception
Return url
End Try
End Function
Private Delegate Sub SetTextCallback(text As String)
Private Sub AppendText(text As String)
If Me.TextBox1.InvokeRequired Then
TextBox1.Invoke(New Action(Of String)(AddressOf AppendText), text)
Return
End If
Me.TextBox1.AppendText(text)
Me.TextBox1.SelectionStart = TextBox1.TextLength
Me.TextBox1.ScrollToCaret()
End Sub
End Class
Class DownloadArgs
Public ReadOnly Url As String
Public ReadOnly Filename As String
Public ReadOnly Client As WebClient
Public Sub New(u As String, f As String, c As WebClient)
Url = u
Filename = f
Client = c
End Sub
End Class
This will successfully download the first 4 files in the UrlQueue, but it then seems to freeze and no further files download. I'd imagine the problem lies in something minor I missed in the process of converting from C# to vb.net, but I can't seem to figure this out.
ClientQueue.Take() blocks the UI thread. Also, WebClient will want to raise the DownloadFileCompleted event on the UI thread - but it is already blocked by ClientQueue.Take(). You have a deadlock.
To resolve this, you got to move your blocking loop to another background thread.
You are blocking the ability for your async queue to process. Not sure this is the "Correct" way to do this but the changes here make it work:
While UrlQueue.Count > 0
Do While ClientQueue.Count = 0
Application.DoEvents()
Loop
Dim cli As WebClient = ClientQueue.Take() ' blocks if there is no client available
Dim url As String = UrlQueue.Dequeue()
Dim fname As String = CreateOutputFilename(url) ' or however you get the output file name
cli.DownloadFileAsync(New Uri(url), fname, New DownloadArgs(url, fname, cli))
End While

VB.NET TCPClient/Server Issue- Sending on a Timer

So my program starts out by counting how many processes of "XProcess" and has a timer to check every 1 second, which works great! I have the input of the count going into Setting variable. I then have a sub routine that takes that Setting variable, along with a IF statement to output that the TCPClient is sending the string ("One Process").
Well the issue is, I have no event to use with the sub routine and so I tied it in with the timer to send the message out every 1 second. The TCPClient sends it to a local address(127.0.0.1) right now, and sends it to a Textbox. Well PROBLEM!!!
It repeats ("One Process") over and over and over, which I can see why this happens.
So with the Code below, how can the TCPClient send an notification of how many processes of "XProcess" to the TCPServer and the TCPSERVER to spit out that 1 or more processes are running ? (with out the SERVER repeating the string (integer works as wel) over and over again)
The below works, but repeats how many processes are running as a string.
MainWindow.xaml.vb
Imports System.Windows.Threading
Imports System.Net.Sockets
Public Class MainWindow
Private Run_ProgramRunCheck_timer As New DispatcherTimer
Private Run_RecieveCheck_timer As New DispatcherTimer
Dim processCount As Integer
Private Sub Window_Loaded(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles MyBase.Loaded
ServerStart()
'Check for program changes every second
' Set interval for timer
Run_ProgramRunCheck_timer.Interval = TimeSpan.FromMilliseconds(1000)
'Start timer on button click
Run_ProgramRunCheck_timer.Start()
AddHandler Run_ProgramRunCheck_timer.Tick, AddressOf __ProgramCheck
'Check for Message Recieve every second
' Set interval for timer
Run_RecieveCheck_timer.Interval = TimeSpan.FromMilliseconds(1000)
'Start timer on button click
Run_RecieveCheck_timer.Start()
AddHandler Run_RecieveCheck_timer.Tick, AddressOf _RecieveMessageConvert
TCPClientSender()
End Sub
Public Sub __ProgramCheck()
'This sub will be checked every 1 seconds for changes
'Count number of processes
processCount = Process.GetProcessesByName("tvnviewer").Count()
My.Settings.TotalProcesses = processCount
End Sub
Public Sub TCPClientSender()
My.Settings.TotalProcesses = 0
If My.Settings.TotalProcesses = 1 Then
Dim port As Int32 = 50000
Dim client As New TcpClient("127.0.0.1", port)
' Translate the passed message into ASCII and store it as a Byte array.
Dim data As [Byte]() = System.Text.Encoding.ASCII.GetBytes("One Process")
' Get a client stream for reading and writing.
' Stream stream = client.GetStream();
Dim stream As NetworkStream = client.GetStream()
' Send the message to the connected TcpServer.
stream.Write(data, 0, data.Length)
End If
End Sub
Public Sub _RecieveMessageConvert()
TextBlock1.Text = My.Settings.StoreSentMessage
End Sub
End Class
TCPServer.vb
Imports System.Net
Imports System.Threading
Imports System.Net.Sockets
Imports System.IO
Public Module TCPServer
Dim Server = New TcpListener(IPAddress.Any, 50000) ' <-- Listen on Port 50,000
Dim Client As New TcpClient
Private ServerThread As Thread = Nothing
Dim Message As String = ""
Private Threads As New List(Of Thread)
Public Sub ServerStart()
ServerThread = New Thread(AddressOf ConnectionListener)
ServerThread.IsBackground = True
ServerThread.Start()
End Sub
Private Sub ConnectionListener()
Try
Server.Start()
While True
Dim client As TcpClient = Server.AcceptTcpClient ' Blocks until Connection Request is Received
Dim Reader As New StreamReader(client.GetStream())
While Reader.Peek > -1
Message = Message + Convert.ToChar(Reader.Read()).ToString
End While
My.Settings.StoreSentMessage = Message
End While
Catch ex As Exception
End Try
End Sub
End Module
Dont you just want to do this:
Dim data As [Byte]() = System.Text.Encoding.ASCII.GetBytes(My.Settings.TotalProcesses)
I dont know how you ever get it to say "One Process" when you set the value to zero and then check if the value is 1 on the next line???
My.Settings.TotalProcesses = 0
If My.Settings.TotalProcesses = 1 Then