Renci.SshNet：“服务器响应不包含ssh协议标识”

Question

我正在 WPF 应用程序上使用 Renci SSH.Net 库，但在使用 SFTP 客户端时遇到问题。当用户尝试连接以从 SFTP 服务器下载一些文件时，他会收到如下所示的消息：

服务器响应不包含 ssh 协议标识

它似乎不是服务器的特定内容，因为我能够在我的开发台式机和辅助笔记本电脑上正常连接和下载文件。同一个应用程序能够通过 SSH 连接并毫无问题地运行命令，只是 SFTP 连接似乎是问题所在。我正在寻找有关从哪里开始解决此问题的一些指导。

SFTP的代码如下所示：

void DownloadPlogs()
    {
        try
        {
            SftpClient SFTP;
            if (GV.UseCustomPort && GV.CustomPort > 0 && GV.CustomPort < 65535)
            {
                SFTP = new SftpClient(GV.IpAddress, GV.CustomPort, GV.Username, GV.Password);
            }
            else
            {
                SFTP = new SftpClient(GV.IpAddress, 22, GV.Username, "");
            }
            SFTP.Connect();

            DownloadDirectory(SFTP, "/PLOG", Directory.GetCurrentDirectory() + @"\PLOG");
            ZipFile.CreateFromDirectory("PLOG", String.Format("{0} - {1} PLOGS.zip", GV.IpAddress, DateTime.Now.ToString("yyyyMMddHHmmss")));
            Directory.Delete(Directory.GetCurrentDirectory() + @"\PLOG", true);

            SFTP.Disconnect();
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message, "Error Getting PLOGS");
        }
    }

    void DownloadDirectory(SftpClient Client, string Source, string Destination)
    {
        var Files = Client.ListDirectory(Source);
        foreach (var File in Files)
        {
            if (!File.IsDirectory && !File.IsSymbolicLink)
            {
                DownloadFile(Client, File, Destination);
            }
            else if (File.IsSymbolicLink)
            {
                //Ignore
            }
            else if (File.Name != "." && File.Name != "..")
            {
                var Dir = Directory.CreateDirectory(System.IO.Path.Combine(Destination, File.Name));
                DownloadDirectory(Client, File.FullName, Dir.FullName);
            }
        }
    }

    void DownloadFile(SftpClient Client, Renci.SshNet.Sftp.SftpFile File, string Directory)
    {
        using (Stream FileStream = System.IO.File.OpenWrite(System.IO.Path.Combine(Directory, File.Name)))
        {
            Client.DownloadFile(File.FullName, FileStream);
        }
    }

SSH 代码如下：

public SshConnection(string Host, int Port, string Username, string Password)
    {
        myClient = new SshClient(Host, Port, Username, Password);
        myClient.KeepAliveInterval = new TimeSpan(0, 0, 5);
        myClient.HostKeyReceived += myClient_HostKeyReceived;
        myClient.ErrorOccurred += myClient_ErrorOccurred;
    }

void myClient_ErrorOccurred(object sender, Renci.SshNet.Common.ExceptionEventArgs e)
    {
        MessageBox.Show(e.Exception.Message, "SSH Error Occurred");
    }

    void myClient_HostKeyReceived(object sender, Renci.SshNet.Common.HostKeyEventArgs e)
    {
        e.CanTrust = true;
    }

    public async void Connect()
    {
        Task T = new Task(() =>
        {
            try
            {
                myClient.Connect();
            }
            catch (System.Net.Sockets.SocketException)
            {
                MessageBox.Show("Invalid IP Address or Hostname", "SSH Connection Error");
            }
            catch (Renci.SshNet.Common.SshAuthenticationException ex)
            {
                MessageBox.Show(ex.Message, "SSH Authentication Error");
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.StackTrace, ex.Message);
                MessageBox.Show(ex.GetType().ToString());
                OnConnection(this, new ConnectEventArgs(myClient.IsConnected));
            }
        });

        T.Start();
        await T;
        if (T.IsCompleted)
        {
            OnConnection(this, new ConnectEventArgs(myClient.IsConnected));
        }
    }

    public void Disconnect()
    {
        try
        {
            myClient.Disconnect();
            OnConnection(this, new ConnectEventArgs(myClient.IsConnected));
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.StackTrace, ex.Message);
        }
    }

    public void SendData(string Data)
    {
        try
        {
            if (Data.EndsWith("\r\n"))
            {
                RunCommandAsync(Data, SshCommandRx);
            }
            else
            {
                RunCommandAsync(String.Format("{0}\r\n",Data), SshCommandRx);
            }
            //SshCommand Command = myClient.RunCommand(Data);
            //OnDataReceived(this, new DataEventArgs(Command.Result));
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.StackTrace, ex.Message);
        }
    }

    private async void RunCommandAsync(String Data, SshCommandCallback Callback)
    {
        Task<SshCommand> T = new Task<SshCommand>(() =>
        {
            try
            {
                SshCommand Command = myClient.RunCommand(Data);
                return Command;
            }

            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, ex.GetType().ToString());
                return null;
            }
        });

        T.Start();
        await T;
        if (T.IsCompleted)
        {
            Callback(this, T.Result);
        }
    }

    private void SshCommandRx(SshConnection C, SshCommand Command)
    {
        if (Command != null)
        {
            string Rx = Command.Result;
            //if (Rx.StartsWith(Command.CommandText))
            //{
            //    Rx = Rx.Remove(0, Command.CommandText.Length);
            //}
            while (Rx.EndsWith("\r\n\r\n") == false)
            {
                Rx += "\r\n";
            }
            OnDataReceived(this, new DataEventArgs(Rx));
        }
    }

Answer 1

我只能通过重试连接来自己解决这个问题。没有找到到底是什么问题，但多次出现此连接问题。

例子：

int attempts = 0;
do
{
    try
    {
        client.Connect();
    }
    catch (Renci.SshNet.Common.SshConnectionException e)
    {
        attempts++;
    }
} while (attempts < _connectiontRetryAttempts && !client.IsConnected);