EnableThreadSafeDataConnections

Question

我使用此库连接到远程FTP服务器并下载库存（csv）文件：https://netftp.codeplex.com/

我已经完成了连接，下载和安装;包装器中的断开序列如下：

class FTPConnection
{
    /// <summary>
    /// Private class objects.
    /// </summary>
    private string ftpHost;
    private string ftpUser;
    private string ftpPass;
    private string ftpDocRoot;
    private int ftpPort;
    private int ftpTimeout;
    private FtpClient ftpClient;

    /// <summary>
    /// Class constructor.
    /// </summary>
    /// <param name="ftpHost"></param>
    /// <param name="ftpPort"></param>
    /// <param name="ftpUser"></param>
    /// <param name="ftpPass"></param>
    /// <param name="ftpDocRoot"></param>
    /// <param name="ftpTimeout"></pparam>
    public FTPConnection(string ftpHost, int ftpPort, string ftpUser, string ftpPass, string ftpDocRoot, int ftpTimeout = 30)
    {
        // Remember settings
        this.ftpHost = ftpHost;
        this.ftpPort = ftpPort;
        this.ftpUser = ftpUser;
        this.ftpPass = ftpPass;
        this.ftpDocRoot = ftpDocRoot;
        this.ftpTimeout = ftpTimeout;
    }

    /// <summary>
    /// Method to test connection.
    /// </summary>
    /// <returns></returns>
    public bool Test()
    {
        // Connect to ftp server
        Connect();

        // Check if connected
        bool isConnected = ftpClient.IsConnected;

        // Disconnect
        Disconnect();

        // Finished
        return isConnected;
    }

    /// <summary>
    /// Method to download stock file from ftp server.
    /// </summary>
    /// <param name="stockFileDir"></param>
    /// <param name="supplierId"></param>
    /// <param name="stockFileNamePattern"></param>
    /// <returns></returns>
    public string DownloadStockFile(string stockFileDir, int supplierId, string stockFileNamePattern)
    {
        // Init
        string localFilePath = "";

        // Connect to ftp server
        Connect();

        // Load remote ftp server files
        foreach (FtpListItem ftpListItem in ftpClient.GetListing(stockFileDir, FtpListOption.Modify | FtpListOption.Size))
        {
            if (ftpListItem.Type == FtpFileSystemObjectType.File && ftpListItem.Name.Contains(stockFileNamePattern))
            {
                localFilePath = string.Format(@"{0}\{1}_{2}", Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location), supplierId, ftpListItem.Name);
                if (File.Exists(localFilePath)) File.Delete(localFilePath);
                using (var ftpStream = ftpClient.OpenRead(ftpListItem.FullName))
                using (var fileStream = File.Create(localFilePath, (int)ftpStream.Length))
                {
                    var buffer = new byte[8 * 1024];
                    int count;
                    while ((count = ftpStream.Read(buffer, 0, buffer.Length)) > 0)
                    {
                        fileStream.Write(buffer, 0, count);
                    }
                    break;
                }
            }
        }

        // Disconnect
        Disconnect();

        // Finished
        return localFilePath;
    }

    /// <summary>
    /// Method to connect to ftp server.
    /// </summary>
    private void Connect()
    {
        // Connect to ftp server
        if (null == ftpClient || !ftpClient.IsConnected)
        {
            ftpClient = new FtpClient();
            ftpClient.Encoding = Encoding.UTF8;
            ftpClient.Host = ftpHost;
            ftpClient.Port = ftpPort;
            ftpClient.ConnectTimeout = 1000 * ftpTimeout;
            ftpClient.Credentials = new NetworkCredential(ftpUser, ftpPass);
            ftpClient.Connect();
            ftpClient.SetWorkingDirectory(ftpDocRoot);
        }
    }

    /// <summary>
    /// Method to disconnect from ftp server.
    /// </summary>
    private void Disconnect()
    {
        try
        {
            ftpClient.Disconnect();
        }
        catch { }
        finally
        {
            if (null != ftpClient)
                ftpClient.Dispose();
            ftpClient = null;
        }
    }
}

这用于“同步”应用程序，该应用程序轮询ftp服务器并按文件名模式抓取第一个匹配的文件。

这就是我使用包装器的方式：

// Init
string stockFilePath = string.Empty;

// Connect to ftp server and download the stock file
FTPConnection ftpConnection = null;
try
{
    // Init connection
    ftpConnection = new FTPConnection
    (
        supplierConfig.FTPHost,
        supplierConfig.FTPPort,
        supplierConfig.FTPUser,
        supplierConfig.FTPPass,
        supplierConfig.FTPDir
    );

    // Download stock file
    stockFilePath = ftpConnection.DownloadStockFile(supplierConfig.FTPDir, supplierConfig.PLSupplierAccountID, supplierConfig.StockFileNamePattern);
}
catch (Exception ex)
{
    // Re throw exception
    throw new Exception("Failed to download stock file - " + ex.Message);
}
finally
{
    // Clean-up
    ftpConnection = null;
}

代码执行时，它完全按预期工作。抓取文件并存储它并返回本地文件的完整路径。

然而，当代码再次执行时（在设定的间隔之后），我不断收到此错误：

已达到您帐户的最大连接数（4）。

但是，您可以在我的包装器中看到我正在关闭ftp连接并处理ftp客户端对象并进行清理。

知道我如何达到4的ftp帐户的最大连接数？

如果我要关闭应用并打开它，它会再次开始正常工作。这是远程ftp服务器的问题吗？它看起来只能连接一次。

Answer 1

您可以尝试将客户端包装在using块中，以查看是否可以重复连接整个对象：

using (FtpClient conn = new FtpClient()) {
     FtpReply reply;

     conn.Host = "localhost";
     conn.Credentials = new NetworkCredential("ftptest", "ftptest");

     if (!(reply = conn.Execute("SITE CHMOD 640 FOO.TXT")).Success) {
         throw new FtpCommandException(reply);
     }
}

Answer 2

ftpConnection = null;没有关闭你的conn，你必须致电ftpConnection.Disconnect()

Answer 3

我已经通过浏览System.Data.FtpClient上的可用选项来解决问题，看看它是否有KeepAlive / MaxConnection等的任何方法/设置....我遇到了这个选项：

EnableThreadSafeDataConnections

以下是此选项的作用：

当此值设置为true（默认值）时，将克隆控件连接以及为数据通道操作建立服务器的新连接。这是一种在单个上进行异步操作的线程安全方法控制连接对开发人员来说是透明的。

所以，我已将此设置为false（因为我没有使用async方法），如下所示：

conn.EnableThreadSafeDataConnections = false;

我的问题解决了。基本上发生了什么，这个库保持连接打开，每次我断开（最多4个）像某种连接池。将此设置为false会阻止它执行此操作。

这是我的代码的最终工作版本：

/// <summary>
/// Method to download stock file from ftp server.
/// </summary>
/// <param name="stockFileDir"></param>
/// <param name="supplierId"></param>
/// <param name="stockFileNamePattern"></param>
/// <returns></returns>
public string DownloadStockFile(string stockFileDir, int supplierId, string stockFileNamePattern)
{
    // Init
    string localFilePath = "";

    // Load remote ftp server file
    using (FtpClient conn = new FtpClient())
    {
        // Set connection details
        conn.Encoding = Encoding.UTF8;
        conn.Host = ftpHost;
        conn.Port = ftpPort;
        conn.ConnectTimeout = 1000 * ftpTimeout;
        conn.Credentials = new NetworkCredential(ftpUser, ftpPass);
        conn.EnableThreadSafeDataConnections = false;

        // Get file listng
        foreach (FtpListItem ftpListItem in conn.GetListing(stockFileDir, FtpListOption.Modify | FtpListOption.Size))
        {
            // Proceed if this is a file
            if (ftpListItem.Type == FtpFileSystemObjectType.File && ftpListItem.Name.Contains(stockFileNamePattern))
            {
                // Download file
                localFilePath = string.Format(@"{0}\{1}_{2}", Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location), supplierId, ftpListItem.Name);
                if (File.Exists(localFilePath)) File.Delete(localFilePath);
                using (var ftpStream = conn.OpenRead(ftpListItem.FullName))
                using (var fileStream = File.Create(localFilePath, (int)ftpStream.Length))
                {
                    var buffer = new byte[8 * 1024];
                    int count;
                    while ((count = ftpStream.Read(buffer, 0, buffer.Length)) > 0)
                    {
                        fileStream.Write(buffer, 0, count);
                    }

                    // Stop further processing
                    break;
                }
            }
        }

        // Disconnect
        conn.Disconnect();
    }

    // Finished
    return localFilePath;
}

希望这有助于某人。

System.Net.FtpClient库

3 个答案:

EnableThreadSafeDataConnections