How do I send a HTTP-command

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It might be quiet similar (so I thought) but I didn't get a way to go.
So I try to get help here - I suppose that it is quiet easy ...
I want to send a HTTP-Command to a Shelly-Device via VB.Net - I work with FORMS and Framework 4.0

The complete command is "http://192.168.xxx.xxx/relay/0?turn=off" for example.
So ... how could I easyly realize that ?

What I have tried:

tried to find a working sample with google but each is either not working or obsolete or after some uses the application freezes.

Posted 13-Nov-23 7:41am

Ralf Meier

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4 solutions

Solution 1

Although your question is not describing the issue which you are facing but from the last part of your question 'application freezes'.

Try to use Asynchronous programming to prevent the UI from freezing while the HTTP request is being sent. Furthermore, ensure that your project has the necessary permissions to access the network while sending request.

Posted 13-Nov-23 8:03am

M Imran Ansari

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Ralf Meier 13-Nov-23 14:41pm

which part isn't clear for you ?
I want to send the HTTP-Command "http://192.168.xxx.xxx/relay/0?turn=off" with the click of a Button for example.
Freezes means that I could send it 2 times and it works and then teh application isn't responsive anymore ...
Don't you have a useful sample for that ?

M Imran Ansari 13-Nov-23 23:31pm

Thank you for sharing the code snippet, I have posted a sample as solution-3.

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Andre Oosthuizen · Accepted Answer · 2023-11-14T07:05:00

I know that a solution has been posted above but thought that my 5 cents worth might help future browsers on the question asked.

I also know that 'HttpClient' is generally considered the newer and more modern option for making HTTP requests in .NET but I have found that 'WebClient' has been around for a longer time and is part of the System.Net namespace. It is simpler and easier to use for basic scenarios but lacks some of the advanced features and flexibility offered by 'HttpClient'. Based on the complexity of your usage, this might be the easier way out if you don't need the more advanced features so if you're looking for a simpler alternative, you might consider using the 'WebClient' class, which is more straightforward for basic scenarios (Tongue in cheek here as many might disagree with me).

To use 'WebClient, you can try the following -

VB.NET

Imports System.Net

Public Class Form1

    Dim webClient As New WebClient()
    Dim baseUrl As String = "http://192.168.178.201/relay/"

    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        SendRequest("0?turn=off")
    End Sub

    Private Sub Button2_Click(sender As System.Object, e As System.EventArgs) Handles Button2.Click
        SendRequest("0?turn=on")
    End Sub

    Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles MyBase.FormClosing
        'Dispose of your WebClient when the form is closing...
        webClient.Dispose()
    End Sub

    Private Sub SendRequest(endpoint As String)
        Try
            Dim result As String = webClient.DownloadString(baseUrl + endpoint)
            'Process the returned result here...
        Catch ex As Exception
            'Handle any exceptions if any is returned...
        End Try
    End Sub

End Class

Ralf Meier · Accepted Answer · 2023-11-13T11:02:00

now I tried it like this - it seems to work ... but perhaps someone has a better Solution ?

VB.NET

Imports System.Net
Imports System.Text

Public Class Form1

    Dim client As WebRequest = WebRequest.Create("http://192.168.178.201/relay/")
    Dim response As WebResponse

    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        client.Method = "POST"
        client = WebRequest.Create("http://192.168.178.201/relay/0?turn=off")
        response = client.GetResponse
        response.Close()
    End Sub

    Private Sub Button2_Click(sender As System.Object, e As System.EventArgs) Handles Button2.Click
        client.Method = "POST"
        client = WebRequest.Create("http://192.168.178.201/relay/0?turn=on")
        response = client.GetResponse()
        response.Close()
    End Sub

End Class

M Imran Ansari · Accepted Answer · 2023-11-13T17:27:00

Thank you for sharing your code snippet. It's good practice to use the Using statement along with an asynchronous method for the WebResponse to ensure that the resources are properly released, even if an exception occurs. Here is the sample which you can use and modify according to your needs.

VB.NET

Imports System.Net.Http

Public Class Form1

    Dim httpClient As New HttpClient()
    Dim baseUrl As String = "http://192.168.178.201/relay/"

    Private Async Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        Await SendRequestAsync("0?turn=off")
    End Sub

    Private Async Sub Button2_Click(sender As System.Object, e As System.EventArgs) Handles Button2.Click
        Await SendRequestAsync("0?turn=on")
    End Sub

    Private Async Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles MyBase.FormClosing
        ' To Make sure to dispose of the HttpClient when the form is closing
        httpClient.Dispose()
    End Sub

    Private Async Function SendRequestAsync(endpoint As String) As Task
        Try
            Using response As HttpResponseMessage = Await httpClient.PostAsync(baseUrl + endpoint, Nothing)
                response.EnsureSuccessStatusCode()
                ' Process the response here
            End Using
        Catch ex As Exception
            ' Handle exceptions if any
        End Try
    End Function

End Class

How do I send a HTTP-command

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