底层连接已关闭：服务器违反了协议

Question

首先对这个琐碎的问题表示抱歉，我是新手，仍在学习。我正在使用 vb.net 构建一个连接到 FTP 服务器的应用程序，列出文件并根据文件扩展名过滤这些文件。然后下载并删除文件。

我收到错误消息：“底层连接已关闭：服务器违反了协议”

这里是我调用方法的地方。

Call GetDirectoryListing(strExtension, strPastaDownload, strUser, strPsswd)
        strFileNumber = Cont_Files
        Dim blnDownloaded As Boolean = False
        If Cont_Files > 0 Then
            For cont = 0 To Cont_Files - 1
                nameFile = arrArq(cont)
                strFilename = UCase(nameFile)
                strLocal = AppPath & strLocalArquivos & "\" & nameFile
                blnDownloaded = mFTP.FtpDownloadFile(strPastaDownload, strNomedoArquivo, strLocal, strUsuario, strSenha)
                StrDir = Dir(strdirectory)
                strRemote = nameFile
                If StrDir <> "" Then
                    FileCopy(AppPath & strfiledirectory & "\" & Trim(strRemote), strLocalBackup & "\" & Trim(strRemote))
                    mFTP.FtpDeleteFile(strServer, strPastaFtp, strFilename, strUsuario, strSenha)
                End If
            Next

这是列出文件的功能，我在这里没有收到任何错误，只是为了说明

  Public Function GetDirectoryListing(ByVal sFilter As String, ByVal strServer As String, ByVal strLogin As String, ByVal strPassword As String) As ArrayList

    Dim ftpRequest As FtpWebRequest = Nothing
    Try
        ftpRequest = FtpWebRequest.Create(New Uri(strServer))
        With ftpRequest
            .Credentials = New NetworkCredential(strLogin, strPassword)
            .UsePassive = True
            .Method = WebRequestMethods.Ftp.ListDirectory
            .KeepAlive = True
        End With
        'ftpRequest.Method = WebRequestMethods.Ftp.ListDirectory  'List, not Download
        'Read the contents of the directory and store it into a string array
        Dim srReader As New StreamReader(ftpRequest.GetResponse().GetResponseStream())
        sDirectoryList = srReader.ReadToEnd().Split(vbNewLine)
        For i As Integer = 0 To UBound(sDirectoryList) - 1
            If sFilter = Mid(sDirectoryList(i), Len(sDirectoryList(i)) - 2, 3) Then
                listaArquivo.Add(sDirectoryList(i))
            End If

        Next

        'Clear the last split vbNewLine
        If sDirectoryList IsNot Nothing Then
            sDirectoryList(sDirectoryList.Length - 1) = ""
        End If

        srReader.Close()
        srReader = Nothing
        GetDirectoryListing = listaArquivo
        ftpRequest = Nothing


    Catch ex As WebException
        MessageBox.Show("Failed to get directory listing. GetDirectoryListing()")
        'MessageBox.Show(ex.ToString())
    End Try

End Function

这里是下载功能

Public Function FtpDownloadFile(ByVal strUrl As String, ByVal strFileName As String, ByVal strTargetDirectory As String, ByVal strLogin As String, ByVal strPassword As String) As Boolean

        Dim ftpRequest As FtpWebRequest = Nothing
        Dim ftpResponse As FtpWebResponse = Nothing
        Dim strFtpFile As String = ""
        Dim strTargetFile As String = ""
        Dim strmReader As StreamReader = Nothing
        Dim strmResponse As Stream = Nothing
        Dim strmTarget As Stream = Nothing
        Dim strmWriter As StreamWriter = Nothing

        strFtpFile = strUrl & "/" & Trim(strFileName)
        strTargetFile = strTargetDirectory

        Try
            ftpRequest = CType(WebRequest.Create(strFtpFile), FtpWebRequest)

            With ftpRequest
                .Credentials = New NetworkCredential(strLogin, strPassword)
                .UsePassive = True
                .Method = WebRequestMethods.Ftp.DownloadFile
                .KeepAlive = True
            End With

            ftpResponse = CType(ftpRequest.GetResponse(), FtpWebResponse) 'line where I am getting the error

            strmTarget = New FileStream(strTargetFile, FileMode.Create)
            strmWriter = New StreamWriter(strmTarget)
            strmResponse = ftpResponse.GetResponseStream()
            strmReader = New StreamReader(strmResponse, System.Text.Encoding.UTF8)
            strmWriter.Write(strmReader.ReadToEnd())

        Catch ex As Exception
            Throw ex

        Finally
        If strmReader IsNot Nothing Then
            strmReader.Close()
            strmReader.Dispose()
        End If

        If strmWriter IsNot Nothing Then
            strmWriter.Close()
            strmWriter.Dispose()
        End If

        If ftpResponse IsNot Nothing Then
            ftpResponse.Close()
            ftpResponse = Nothing
        End If


        If ftpRequest IsNot Nothing Then ftpRequest = Nothing
    End Try


    Return True

End Function

提前感谢您的帮助

Answer 1

我认为问题在于您将WebRequest 转换为FtpWebRequest 的行上的FtpDownloadFile 方法。它们不一样。

ftpRequest = FtpWebRequest.Create(New Uri(strServer))
ftpRequest = CType(WebRequest.Create(strFtpFile), FtpWebRequest)

尝试确保每次都以相同的方式连接到服务器。使用行之有效的方式。