Testing using Plink.exe to connect to SSH in C#

Question

Im trying to connect to a unix terminal via plink.exe. The goal is so that I can read the text back into a string.

My dilema is that the bank I work for uses an old

Answer 1

So I just wanted to test plink myself and well it's result were pretty pleasing.

As I said in the comments you can't use ReadToEnd before you send the exit command, unless you want to block your current Thread.

Actually you could just send a bunch of commands (including the exit or logout) before engaging the ReadToEnd, but I did suggest to do the Read asynchrounusly as it is more robust.

Now there are a few ways to do async reading of a stream.

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The Process class actually provides Events that are raised on incoming data. You could create handlers for those Events. These Events are:

• OutputDataReceived
• ErrorDataReceived

Their event handlers provide strings containing the data.

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You could use the BeginRead of the StreamReader instances of stdout/stdin.

But here I provide a code sample that does it in a more crude way using simple multi-threading:

  public string RequestInfo(string remoteHost, string userName, string password, string[] lstCommands) {
        m_szFeedback = "Feedback from: " + remoteHost + "\r\n";

        ProcessStartInfo psi = new ProcessStartInfo()
        {
            FileName = PLINK_PATH, // A const or a readonly string that points to the plink executable
            Arguments = String.Format("-ssh {0}@{1} -pw {2}", userName, remoteHost, password),
            RedirectStandardError = true,
            RedirectStandardOutput = true,
            RedirectStandardInput = true,
            UseShellExecute = false,
            CreateNoWindow = true
        };

        Process p = Process.Start(psi);

        m_objLock = new Object();
        m_blnDoRead = true;

        AsyncReadFeedback(p.StandardOutput); // start the async read of stdout
        AsyncReadFeedback(p.StandardError); // start the async read of stderr

        StreamWriter strw = p.StandardInput;

        foreach (string cmd in lstCommands)
        {
            strw.WriteLine(cmd); // send commands 
        }
        strw.WriteLine("exit"); // send exit command at the end

        p.WaitForExit(); // block thread until remote operations are done
        return m_szFeedback;
    }

    private String m_szFeedback; // hold feedback data
    private Object m_objLock; // lock object
    private Boolean m_blnDoRead; // boolean value keeping up the read (may be used to interrupt the reading process)

    public void AsyncReadFeedback(StreamReader strr)
    {
        Thread trdr = new Thread(new ParameterizedThreadStart(__ctReadFeedback));
        trdr.Start(strr);
    }
    private void __ctReadFeedback(Object objStreamReader)
    {
        StreamReader strr = (StreamReader)objStreamReader; 
        string line;          
        while (!strr.EndOfStream && m_blnDoRead) 
        {
            line = strr.ReadLine();
            // lock the feedback buffer (since we don't want some messy stdout/err mix string in the end)
            lock (m_objLock) { m_szFeedback += line + "\r\n"; }
        }
    }

So if you want to get the contents of the user directory of a remote host call:

String feedback = RequestInfo("remote.ssh.host.de", "user", "password", new string[] { "ls -la" });

Obviously you substitute your own address, credentials and command-list.

Also you might want to clean the output string. e.G. in my case the commands I send to the remotehost are echoed into the output and thus appear in the return string.

Answer 2

Hey the above code worked partially for me but it was good help i juts replaced the contractor parameters as follows

const string PLINK_PATH = @"C:\Program Files (x86)\PuTTY\plink.exe";

        Process p = new Process();

        // Redirect the output stream of the child process.
        p.StartInfo.UseShellExecute = false;
        p.StartInfo.RedirectStandardInput = true;
        p.StartInfo.RedirectStandardOutput = true;
        p.StartInfo.RedirectStandardError = true;           
        p.StartInfo.FileName = PLINK_PATH;            
        p.StartInfo.Arguments = String.Format(" -ssh {0}@{1} -pw {2}", userName, remoteHost, password);

Hope this helps with above code....