双向使用Webclient进行二进制

Question

Webclient 用于将指令文件（最大 1 兆字节）上传到服务器，并以二进制数据的形式接收此操纵的指令集作为响应（最大 1 兆字节）。

我能够上传二进制文件和下载二进制文件，但我无法使用相同的请求/响应命令来完成。意味着，不是同一个 webclient 可以做到这一点。在这种情况下，它会丢失对服务器上设置的流的引用。

如何在一个序列中写入和读取二进制数据？

.

服务器脚本

Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest

            'Setup data reader
            If cRead Is Nothing Then cRead = New ReadDataFromContext
            cRead.Read(context) 'read data from 'context.Request.InputStream'


            If cWrite Is Nothing Then cWrite = New WriteDataToContext
            cWrite.Write(context) 'write data to 'context.Response.OutputStream'


        End Sub

.

客户端类

Partial Public Class MainPage
    Inherits UserControl
    Private WithEvents WCUpload As WebClient
    'Private WithEvents WCDownload As WebClient
    Private Stream As IO.Stream

    Dim U As New Uri("http://localhost:51001/communicator.ashx", UriKind.Absolute)


    Public Sub New()
        InitializeComponent()
        WCUpload = New WebClient
        'WCDownload = New WebClient

    End Sub

    Private Sub btnTest_Click(sender As System.Object, e As System.Windows.RoutedEventArgs) Handles btnTest.Click
        WCUpload.OpenWriteAsync(U)
    End Sub


    'This methode is never called if using WCUpload (on WCDownload it works but WCDownload has no more data)
    'Private Sub WC_OpenReadCompleted(sender As Object, e As System.Net.OpenReadCompletedEventArgs) Handles WCDownload.OpenReadCompleted
    '    Dim D(e.Result.Length - 1) As Byte
    '    e.Result.Read(D, 0, D.Length)
    '    Me.btnTest.Content = System.Text.Encoding.UTF8.GetString(D, 0, D.Length)
    'End Sub

    Private Sub WC_OpenWriteCompleted(sender As Object, e As System.Net.OpenWriteCompletedEventArgs) Handles WCUpload.OpenWriteCompleted
        Me.Stream = e.Result

        Dim D() As Byte = System.Text.Encoding.UTF8.GetBytes("Hallo Timo")
        Me.Stream.Write(D, 0, D.Length)
        Me.Stream.Close()
    End Sub

    Private Sub WC_WriteStreamClosed(sender As Object, e As System.Net.WriteStreamClosedEventArgs) Handles WCUpload.WriteStreamClosed
        'WC.OpenReadAsync(U)

        'WCDownload.OpenReadAsync(U)

        Me.Stream.Position = 0 '<<--- ERROR, cannot access to disposed object
        Dim D(Me.Stream.Length - 1) As Byte
        Me.Stream.Read(D, 0, D.Length)
        Me.btnTest.Content = System.Text.Encoding.UTF8.GetString(D, 0, D.Length)

    End Sub

    Public Sub PushData(ByVal StreamIn As IO.Stream, ByVal StreamOut As IO.Stream)
        Dim Buffer(4096 - 1) As Byte
        Dim BytesRead As Integer
        On Error Resume Next

        'RaiseEvent Progress(Me, 0)

        Do
            BytesRead = StreamIn.Read(Buffer, 0, Buffer.Length)
            If BytesRead <= 0 Then Exit Do
            StreamOut.Write(Buffer, 0, BytesRead)
            'RaiseEvent Progress(Me, StreamOut.Length / StreamIn.Length * 99) 'max 99 to raise the event with 100%
        Loop

        'RaiseEvent Progress(Me, 100)
    End Sub
End Class

Answer 1

在我看来，您只是在寻找UploadData 方法，该方法将byte[] 请求主体发送到服务器，并将byte[] 响应主体返回给客户端。简单如：

byte[] req = ...;
byte[] resp;
using(var client = new WebClient()) {
    resp = client.UploadData(address, req);
}

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归根结底，http 是一种请求/响应协议——不过，您可以按顺序执行多个请求。如果您需要更大的灵活性，我建议您查看允许两端临时发送的 web-sockets。

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对于 silverlight 的异步使用，请尝试 PCL 版本的 HttpClient - 类似的 api，但比 silverlight 提供的开箱即用的实现更完整：http://blogs.msdn.com/b/bclteam/archive/2013/02/18/portable-httpclient-for-net-framework-and-windows-phone.aspx