VB.net 通过 HttpWebRequest POST

Question

我正在尝试使用以下代码向 LAN 上的 Arduino 以太网微控制器发送命令：

Dim request As HttpWebRequest = HttpWebRequest.Create("http://192.178.47.19:19/?r=")
Dim POST As String = "r1"

request.Method = "POST"
request.ContentType = "text/html"
request.Headers.Add("Access-Control-Allow-Origin: *")
request.ContentLength = POST.Length
request.KeepAlive = True

Dim requestStream As Stream = request.GetRequestStream()
Dim postBytes As Byte() = Encoding.ASCII.GetBytes(POST)
requestStream.Write(postBytes, 0, postBytes.Length)
requestStream.Close()

但是，我在线收到错误：

Dim requestStream As Stream = request.GetRequestStream()

这样说：

底层连接已关闭：连接意外关闭。

仅使用 jQuery 和 AJAX：

jQuery.support.cors = true;

  $.ajax({
        crossDomain: true,
        async : true,
        type: "POST",
        headers: {'Access-Control-Allow-Origin': '*'},
        url: "http://192.178.47.19:19/?r=" + whatsBeingSent,
        data: '{}',
        contentType: "text/html",
        dataType: "html",
        success: OnSuccessCallArduino,
        error: OnErrorCallArduino
  });

使用上面的代码效果很好（当然在浏览器中）

那么为了让它在 VB.net 中运行，我会缺少什么？

Answer 1

我也有类似的问题。我在浏览器客户端中使用 jQuery AJAX 调用来访问 aspx 文件，该文件运行生成 WebRequest 响应的函数。这通常可以正常工作，不会出现任何问题。但是，如果该函数使用 WebRequest 访问不同的服务器，则响应良好，但永远不会返回到原始 AJAX 调用，并且应用程序会挂起。

浏览器 AJAX：

    $.ajax({ dataType: "text", type: "POST", url: "WSProfile.aspx", async: false, data: { oper: 'FunctionSpecification', Data1: d1, Data2: d2 }, success: function (msg) { alert(msg); } });

WSProfile.Aspx：

    Dim d1 As Text = Request.Form("Data1")
    Dim d2 As Text = Request.Form("Data2")

    Function getResponse(d1, d2)

    Dim request As WebRequest = WebRequest.Create("http://urlname.com")
    request.Method = "POST"
    Dim postData As String = "data1=" & d1 & "&data2=" & d2
    Dim byteArray As Byte() = System.Text.Encoding.UTF8.GetBytes(postData)
    request.ContentType = "application/x-www-form-urlencoded"
    request.ContentLength = byteArray.Length
    Dim dataStream As Stream = request.GetRequestStream()
    dataStream.Write(byteArray, 0, byteArray.Length)
    dataStream.Close()
    Dim response As WebResponse = DirectCast(request.GetResponse(), HttpWebResponse)
    Dim Status As String = CType(response, HttpWebResponse).StatusDescription
        dataStream = response.GetResponseStream()
    Dim reader As New StreamReader(dataStream)

    Response.Write(reader.ReadToEnd())
    Response.Flush()

对另一个 URL 的调用会返回响应，但对

.aspx

文件的原始调用的 Response.Write 永远不会将数据返回到 jQuery AJAX 调用。