Convert C to vbnet

Question

I have an existing vbnet program. With this I want to make a connection with a SSE server send events from openhab.
I have found a basic program but it is in C, so I'm trying to convert it to vb.
I don' have error anymore in studio but it doesn't run.
It stops with the line:
Using StreamReader As New StreamReader(Await client.GetStreamAsync(url))

Anyone an Idea. Or maybe a starting point for vbnet ? Or an example in vbnet?

C:
namespace ConsoleApp2
{
class Program
{
static async Task Main(string[] args)
{
HttpClient client = new HttpClient();
client.Timeout = TimeSpan.FromSeconds(5);
string url = $"http://localhost:8080/rest/events";
while (true)
{
try
{
Console.WriteLine("Establishing connection");
using (var streamReader = new StreamReader(await client.GetStreamAsync(url)))
{
while (!streamReader.EndOfStream)
{
var message = await streamReader.ReadLineAsync();
Console.WriteLine($"Received message: {message}");
}
}
}
catch (Exception ex)
{
//Here you can check for
//specific types of errors before continuing
//Since this is a simple example, i'm always going to retry
Console.WriteLine($"Error: {ex.Message}");
Console.WriteLine("Retrying in 5 seconds");
await Task.Delay(TimeSpan.FromSeconds(5));
}
}
}
}
}

vbnet

Module Program
Public Sub Main(args As String())
ReadAndDisplayAsync()
End Sub

Async Sub ReadAndDisplayAsync()
    Dim client As HttpClient = New HttpClient()
    client.Timeout = TimeSpan.FromSeconds(5)
    Dim url As String = $"http://localhost:8080/rest/events"
    While (True)
        Try
            Console.WriteLine("Establishing connection")
            'Dim aaa As Stream = Await client.GetStreamAsync(url)
            Using StreamReader As New StreamReader(Await client.GetStreamAsync(url))
                'Using streamReader As New StreamReader(await client.GetStreamAsync(url))
                While (Not StreamReader.EndOfStream)
                    Dim message = Await StreamReader.ReadLineAsync()
                    Console.WriteLine($"Received price update: {message}")
                End While
            End Using
        Catch ex As Exception
            Console.WriteLine("xxxx")
            '//Here you can check for 
            '//specific types of errors before continuing
            '//Since this Is a simple example, i'm always going to retry
            Console.WriteLine($"Error: {ex.Message}")
            Console.WriteLine("Retrying in 5 seconds")
            'await Task.Delay(TimeSpan.FromSeconds(5))
            'Task.Delay(TimeSpan.FromSeconds(5))
            'Dim result As String = Await WaitAsynchronouslyAsync()
            WaitAsynchronouslyAsync()
        End Try
    End While
End Sub
Public Async Function WaitAsynchronouslyAsync() As Task(Of String)
    Await Task.Delay(10000)
    Return "Finished"
End Function

End Module

Answer 1

Hi @Pieter Souvereyns ,

The VB. NET code converted from C# is :

Async Function Main(ByVal args As String()) As Task  
    Dim client As HttpClient = New HttpClient()  
    client.Timeout = TimeSpan.FromSeconds(5)  
    Dim url As String = $"http://localhost:8080/rest/events"  
    Dim isDelay = False  
    While True  

        Try  
            Console.WriteLine("Establishing connection")  

            Using streamReader = New StreamReader(Await client.GetStreamAsync(url))  

                While Not streamReader.EndOfStream  
                    Dim message = Await streamReader.ReadLineAsync()  
                    Console.WriteLine($"Received message: {message}")  
                End While  
            End Using  
            isDelay = False  
        Catch ex As Exception  
            Console.WriteLine($"Error: {ex.Message}")  
            Console.WriteLine("Retrying in 5 seconds")  
            isDelay = True  
        End Try  
        If isDelay Then  
            Await Task.Delay(TimeSpan.FromSeconds(5))  
        End If  
    End While  
End Function  

Give it a try and if you get any exceptions, please provide a detailed description of the exception.
Hope it could be helpful.

Best Regards,
Jack

Answer 2

It give the same problem.
At line "Using streamReader = New StreamReader(Await client.GetStreamAsync(url))"
It displays:
(process 11040) exited with code 0.
To automatically close the console when debugging stops, enable Tools->Options->Debugging->Automatically close the console when debugging stops.
Press any key to close this window . . .
Because visual is complaining about the main, I hve tried to put it after a button on a form.
There it does his job. This i my goal to put it on a form.
But he takes the focus to that sub and the form isn't reachabel anymore.
Is it possible to avoid this?

Answer 3

See if this will work for you.

• One button to run
• One button to cancel (for errors), you could also setup a timeout or use a counter where if hit terminate the process. Imports System.IO
  Imports System.Net.Http
  Imports System.Threading Public Class Form1

  Private _cancellationTokenSource As New CancellationTokenSource()
  
  Private Async Function Demo(token As CancellationToken, secondsDelay As Integer) As Task(Of String)
  
      While True
          Try
  
              Await Task.Delay(secondsDelay, token)
  
              Using client = New HttpClient()
  
                  Dim response = Await client.GetAsync("http://httpbin.org/get",
                                               HttpCompletionOption.ResponseHeadersRead)
  
                  response.EnsureSuccessStatusCode()
  
                  Using stream = Await response.Content.ReadAsStreamAsync()
                      Using streamReader As New StreamReader(stream)
                          Return Await streamReader.ReadToEndAsync()
                      End Using
                  End Using
              End Using
  
          Catch httpRequestException As HttpRequestException
              Const msg = "Response status code does not indicate success: 404 (NOT FOUND)."
              If httpRequestException.Message.Contains(msg) Then
                  Console.WriteLine("404 error")
              End If
  
              If token.IsCancellationRequested Then
                  token.ThrowIfCancellationRequested()
                  Return String.Empty
              End If
  
          Catch generalException As Exception
              Console.WriteLine(generalException.Message)
          End Try
      End While
  
      Return String.Empty
  
  End Function
  
  Private Async Sub RunButton_Click(sender As Object, e As EventArgs) Handles RunButton.Click
  
      If _cancellationTokenSource.IsCancellationRequested Then
          _cancellationTokenSource.Dispose()
          _cancellationTokenSource = New CancellationTokenSource()
      End If
  
      Try
          Dim contents = Await Demo(_cancellationTokenSource.Token, 5)
          Console.WriteLine(contents)
      Catch ex As Exception
          Console.WriteLine("Failed")
      End Try
  
  End Sub
  
  Private Sub CancelDemo2Button_Click(sender As Object, e As EventArgs) Handles CancelDemo2Button.Click
      _cancellationTokenSource.Cancel()
  End Sub
  

  End Class

In the above we expect

{
  "args": {}, 
  "headers": {
    "Host": "httpbin.org", 
    "X-Amzn-Trace-Id": "Root=1-6050ae05-0398eea53b2d18322a42d8e8"
  }, 
  "origin": "159.121.204.129", 
  "url": "http://httpbin.org/get"
}

Answer 4

It gives your output.
So I changed the url.
This stops with the ReadToEndAsync, this doens't return with the openhab server
I change ReadToEndAsync to ReadLineAsync
And the While token.IsCancellationRequested = False also in the runbutton.
This works for a part because I have to read more lines.
Tried with a While (Not streamReader.EndOfStream) but then I get the same that he doesn't return

When I debug and look at the straeamreader i get when it is freezing and returning to the main application this message
]1
'system.io.streamreader.enofstream.get' timed out and needed to be aborted in an unsafe way. This may have corrupted the target process.