Description

The SSH protocol allows for the remote execution of commands on the server. This is done using a SSH logical channel. Many SSH features like SFtp and remote command execution are implemented over such channels. Every channel is multiplexed into a single encrypted SSH connection.

As such, a remote command execution can be issued while a SFtp session is performing work since a new channel will be created to issue the command.

Remote command execution works by the client sending a message that requests the server start the execution of a given command string. The 'command' string may contain a path and arguments. It is also possible to pass environment variables to the server before the command is executed.

It should be noted that servers will take normal precautions to prevent the execution of unauthorized commands. At the very least, this means that the right to execute a command, and which commands are allowed will depend on the user that is authenticated on the SSH connection. These rights are determined by the server's administrator and cannot be computed on the client side.

If a user doesn't have the rights to execute a command, an exception will be thrown but the SSH connection will not be closed. Other channels (like SFtp sessions) will continue to proceed without issue.

Usage

A remote command is executed using the Xceed.SSH.Client.ExecuteCommandSession Class. Its constructor needs to be supplied a SSHClient object that is connected and authenticated. Then, the Connect() method can be called, specifying the command to execute and, optionally, environment variables to set on the server before the command is executed.

The ExecuteCommandSession class is ony available with the Xceed SFtp for .NET that is compiled for .NET 4.0 and later. The class is available with Xceed SFtp for Xamarin, all versions.

The Connect() method returns immediately if the server accepts the command. If not, a SSHChannelRequestFailedException is thrown. The command is run on the server while control continues normall on the client side. The server might send standard output and/or standard error text output to the client. It is possible to catch that data with a Stream object using the GetOutputStream() and GetErrorStream() methods. It is also possible to send text to the command's standard input using a stream with the GetInputStream() method. With all these streams, it is often useful to wrap them around a System.Text.StreamReader or System.Text.StreamWriter object to read and write text lines. See the examples below for details.

The ExecuteCommandSession class contains a CommandCompleted Event event that will be triggered when the command has completed on the server. At that point, the channel will have been closed but the possible exit status or exit signal (not all servers supply these values) will still be available to be read.

Another way to watch for the completion of the command is to wait on the SessionCompletedWaitHandle.

The ExecuteCommandSession class implements the IDisposable interface. It is good practice to dispose of an instance of the class once it is no longer needed.

Examples

Execute and wait for result

The simplest way to use the ExecuteCommandSession class is to start the command and wait for the command to complete.

C#
VB.NET

using System.IO;



using Xceed.SSH.Client;

using Xceed.SSH.Core;

using Xceed.SSH.Protocols;

using Xceed.FileSystem;



namespace DocumentationExamples.SSH

{

  public class ExecuteCommandSession3

  {

    public void Example()

    {

      string host = "localhost";

      string username = "normal1";

      string password = "normal1";



      SSHClient ssh = new SSHClient();



      // Connect to the host

      ssh.Connect( host );



      try

      {

        // Log in

        ssh.Authenticate( username, password );



        // The remote command to execute

        string command = "dir";



        // Create a session that will execute a remote command

        using( ExecuteCommandSession executeCommandSession = new ExecuteCommandSession( ssh ) )

        {

          // Execute the command on the remote server, waiting until it completes

          Nullable<int> exitStatus = executeCommandSession.ExecuteCommand( command );



          /* Some servers will return exit information like the return code and the 'signal'

             if the command fails. */



          Console.WriteLine( "Command exited with status {0}", exitStatus.HasValue ? exitStatus.ToString() : "(null)" );



          SSHChannelExitSignal exitSignal = executeCommandSession.ExitSignal;

          if( exitSignal != null )

          {

            Console.WriteLine( "Command exited with signal {0}: {1}", exitSignal.SignalName, exitSignal.ErrorMessage );

          }

        }

      }

      catch( SSHChannelRequestFailedException )

      {

        /* This exception is thrown by ExecuteCommandSession.Connect(). The most common

         * cause is the authenticated user does not have the rights to execute commands

         * on the server. */

      }

      finally

      {

        // Always make sure to disconnect from the server when the connection is no longer needed

        ssh.Disconnect();

      }

    }

  }

}

Imports System.IO



Imports Xceed.SSH.Client

Imports Xceed.SSH.Core

Imports Xceed.SSH.Protocols

Imports Xceed.FileSystem



Namespace DocumentationExamples.SSH

  Public Class ExecuteCommandSession3

    Public Sub Example()

      Dim host As String = "localhost"

      Dim username As String = "normal1"

      Dim password As String = "normal1"



      Dim ssh As New SSHClient()



      ' Connect to the host

      ssh.Connect(host)



      Try

        ' Log in

        ssh.Authenticate(username, password)



        ' The remote command to execute

        Dim command As String = "dir"



        ' Create a session that will execute a remote command

        Using executeCommandSession As New ExecuteCommandSession(ssh)

          ' Execute the command on the remote server, waiting until it completes

          Dim exitStatus As Nullable(Of Integer) = executeCommandSession.ExecuteCommand(command)



'           Some servers will return exit information like the return code and the 'signal'

'             if the command fails. 



          Console.WriteLine("Command exited with status {0}",If(exitStatus.HasValue, exitStatus.ToString(), "(null)"))



          Dim exitSignal As SSHChannelExitSignal = executeCommandSession.ExitSignal

          If exitSignal IsNot Nothing Then

            Console.WriteLine("Command exited with signal {0}: {1}", exitSignal.SignalName, exitSignal.ErrorMessage)

          End If

        End Using

      Catch e1 As SSHChannelRequestFailedException

'         This exception is thrown by ExecuteCommandSession.Connect(). The most common

'         * cause is the authenticated user does not have the rights to execute commands

'         * on the server. 

      Finally

        ' Always make sure to disconnect from the server when the connection is no longer needed

        ssh.Disconnect()

      End Try

    End Sub

  End Class

End Namespace

Fire-and-forget

The ExecuteCommandSession class can also be used in a fire-and-forget manner.

C#
VB.NET

using System.IO;

using System.Threading.Tasks;



using Xceed.SSH.Client;

using Xceed.SSH.Core;

using Xceed.SSH.Protocols;

using Xceed.FileSystem;



namespace DocumentationExamples.SSH

{

  public class ExecuteCommandSession4

  {

    public void Example()

    {

      string host = "localhost";

      string username = "normal1";

      string password = "normal1";



      // The remote command to execute

      string command = "dir";



      SSHClient ssh = new SSHClient();



      // Connect to the host

      ssh.Connect( host );



      try

      {

        // Log in

        ssh.Authenticate( username, password );



        Task<Nullable<int>> task = this.ExecuteRemoteCommandAsync( ssh, command );



        /* TODO: Perform other business that does not require the result of the remote command */



        /* Now that we need the result from the remote command, we will wait for it */

        Nullable<int> exitStatus = task.Result;

        Console.WriteLine( "Command exited with status {0}", exitStatus.HasValue ? exitStatus.ToString() : "(null)" );

      }

      finally

      {

        // Always make sure to disconnect from the server when the connection is no longer needed

        ssh.Disconnect();

      }

    }



    private async Task<Nullable<int>> ExecuteRemoteCommandAsync( SSHClient ssh, string command )

    {

      Task<Nullable<int>> executeCommandTask;

      Nullable<int> exitStatus;



      ExecuteCommandSession executeCommandSession = null;



      // Create a session that will execute a remote command

      executeCommandSession = new ExecuteCommandSession( ssh );



      try

      {

        // Start executing the specified command on the remote server

        executeCommandTask = executeCommandSession.ExecuteCommandAsync( command );

      }

      catch( SSHChannelRequestFailedException )

      {

        /* This exception is thrown by ExecuteCommandSession.Connect(). The most common

          * cause is the authenticated user does not have the rights to execute commands

          * on the server. */



        /* The 'CommandCompleted' event is not triggered when the request to launch the command fails */



        // Dispose of the session to free resources

        executeCommandSession.Dispose();



        // Rethrow the exception

        throw;

      }



      // Wait for the remote command to complete while allowing the calling method to continue execution

      exitStatus = await executeCommandTask;



      /* This code will be executed in a background thread from ThreadPool */



      // Dispose of the session to free resources

      executeCommandSession.Dispose();



      return exitStatus;

    }

  }

}

Imports System.IO

Imports System.Threading.Tasks



Imports Xceed.SSH.Client

Imports Xceed.SSH.Core

Imports Xceed.SSH.Protocols

Imports Xceed.FileSystem



Namespace DocumentationExamples.SSH

  Public Class ExecuteCommandSession4

    Public Sub Example()

      Dim host As String = "localhost"

      Dim username As String = "normal1"

      Dim password As String = "normal1"



      ' The remote command to execute

      Dim command As String = "dir"



      Dim ssh As New SSHClient()



      ' Connect to the host

      ssh.Connect(host)



      Try

        ' Log in

        ssh.Authenticate(username, password)



        Dim task As Task(Of Nullable(Of Integer)) = Me.ExecuteRemoteCommandAsync(ssh, command)



        ' TODO: Perform other business that does not require the result of the remote command 



        ' Now that we need the result from the remote command, we will wait for it 

        Dim exitStatus As Nullable(Of Integer) = task.Result

        Console.WriteLine("Command exited with status {0}",If(exitStatus.HasValue, exitStatus.ToString(), "(null)"))

      Finally

        ' Always make sure to disconnect from the server when the connection is no longer needed

        ssh.Disconnect()

      End Try

    End Sub



    Private async Function ExecuteRemoteCommandAsync(ByVal ssh As SSHClient, ByVal command As String) As Task(Of Nullable(Of Integer))

      Dim executeCommandTask As Task(Of Nullable(Of Integer))

      Dim exitStatus As Nullable(Of Integer)



      Dim executeCommandSession As ExecuteCommandSession = Nothing



      ' Create a session that will execute a remote command

      executeCommandSession = New ExecuteCommandSession(ssh)



      Try

        ' Start executing the specified command on the remote server

        executeCommandTask = executeCommandSession.ExecuteCommandAsync(command)

      Catch e1 As SSHChannelRequestFailedException

'         This exception is thrown by ExecuteCommandSession.Connect(). The most common

'          * cause is the authenticated user does not have the rights to execute commands

'          * on the server. 



        ' The 'CommandCompleted' event is not triggered when the request to launch the command fails 



        ' Dispose of the session to free resources

        executeCommandSession.Dispose()



        ' Rethrow the exception

        Throw

      End Try



      ' Wait for the remote command to complete while allowing the calling method to continue execution

      exitStatus = await executeCommandTask



      ' This code will be executed in a background thread from ThreadPool 



      ' Dispose of the session to free resources

      executeCommandSession.Dispose()



      Return exitStatus

    End Function

  End Class

End Namespace

Capture command output

The output of the command can be captured. Here a technique using asynchronous reading is used in order to read output and error text at the same time.

Also shown in this example is how to pass environment variables to the server.

C#
VB.NET

using System.Collections.Generic;

using System.IO;

using System.Threading;

using System.Threading.Tasks;



using Xceed.SSH.Client;

using Xceed.SSH.Core;

using Xceed.SSH.Protocols;

using Xceed.FileSystem;



namespace DocumentationExamples.SSH

{

  public class ExecuteCommandSession1

  {

    public void Example()

    {

      string host = "localhost";

      string username = "normal1";

      string password = "normal1";



      SSHClient ssh = new SSHClient();



      // Connect to the host

      ssh.Connect( host );



      try

      {

        // Log in

        ssh.Authenticate( username, password );



        // The remote command to execute

        string command = "dir *.*";



        // Some environment variables

        KeyValuePair<string, string> environmentVariable = new KeyValuePair<string, string>( "MYVARIABLE", "MYVALUE" );



        // Create a session that will execute a remote command

        using( ExecuteCommandSession executeCommandSession = new ExecuteCommandSession( ssh ) )

        {

          Stream commandOutputStream = null;

          Stream commandErrorStream = null;



          try

          {

            /* We obtain the output and error streams BEFORE starting the command so that we don't

               miss any output. */



            /* If the CommandOutputStream or the CommandErrorStream object is not taken,

               the component silently discards the incoming data. This might be desirable if

               the output and/or error text is not needed. */



            // Get the command's output stream (standard output)

            commandOutputStream = executeCommandSession.GetOutputStream();



            // Get the command's error stream (standard error)

            commandErrorStream = executeCommandSession.GetErrorStream();



            /* Now that we are setup the way we want, we can safely start the remote command */



            // Start executing the specified command on the remote server passing the supplied environment variables to the server

            executeCommandSession.Connect( command, environmentVariable );



            /* Notice how we wrap the streams with StreamReader objects only after starting the command.

               This guards against the possibility of the StreamReader object calling Stream.Read() before

               we've started the command. */



            // Wrap a stream reader around the output stream

            System.IO.StreamReader outputReader = new System.IO.StreamReader( commandOutputStream );



            // Wrap a stream reader around the error stream

            System.IO.StreamReader errorReader = new System.IO.StreamReader( commandErrorStream );



            // Read a line from the output and error at the same time

            Task<string> readOutputLineTask = outputReader.ReadLineAsync();

            Task<string> readErrorLineTask = errorReader.ReadLineAsync();



            string line;



            // While either the output or error streams haven't reached end-of-file

            while( readOutputLineTask != null || readErrorLineTask != null )

            {

              // If reading an output line has completed

              if( readOutputLineTask != null && readOutputLineTask.IsCompleted )

              {

                // Get the line

                line = readOutputLineTask.Result;



                // If we have a line

                if( line != null )

                {

                  // Output it to the console

                  Console.WriteLine( line );



                  // Read another line

                  readOutputLineTask = outputReader.ReadLineAsync();

                }

                else

                {

                  /* We've reached end-of-file. We don't want to read again */

                  readOutputLineTask = null;

                }

              }



              // If reading an error line has completed

              if( readErrorLineTask != null && readErrorLineTask.IsCompleted )

              {

                // Get the line

                line = readErrorLineTask.Result;



                // If we have a line

                if( line != null )

                {

                  // Output it to the console

                  Console.WriteLine( line );



                  // Read another line

                  readErrorLineTask = errorReader.ReadLineAsync();

                }

                else

                {

                  /* We've reached end-of-file. We don't want to read again */

                  readErrorLineTask = null;

                }

              }

            }



            /* Because we've processed the output stream until end-of-file, we are sure that

              the command has completed. No need to wait. 



               However, if accessing the exit status or possible exit signal of the command

               is important to the application, it is best to wait until the command has signaled it

               has completed. At that point, the exit information will have been received. */



            // Wait until the command has completed

            executeCommandSession.SessionCompletedWaitHandle.WaitOne();



            /* Some servers will return exit information like the return code and the 'signal'

              if the command fails. */



            Nullable<int> exitStatus = executeCommandSession.ExitStatus;

            Console.WriteLine( "Command exited with status {0}", exitStatus.HasValue ? exitStatus.ToString() : "(null)" );



            SSHChannelExitSignal exitSignal = executeCommandSession.ExitSignal;

            if( exitSignal != null )

            {

              Console.WriteLine( "Command exited with signal {0}: {1}", exitSignal.SignalName, exitSignal.ErrorMessage );

            }

          }

          catch( SSHChannelRequestFailedException )

          {

            /* This exception is thrown by ExecuteCommandSession.Connect(). The most common

             * cause is the authenticated user does not have the rights to execute commands

             * on the server. */

          }

          finally

          {

            if( commandOutputStream != null )

            {

              commandOutputStream.Close();

              commandOutputStream = null;

            }



            if( commandErrorStream != null )

            {

              commandErrorStream.Close();

              commandErrorStream = null;

            }

          }

        }



      }

      finally

      {

        // Always make sure to disconnect from the server when the connection is no longer needed

        ssh.Disconnect();

      }

    }

  }

}

Imports System.Collections.Generic

Imports System.IO

Imports System.Threading

Imports System.Threading.Tasks



Imports Xceed.SSH.Client

Imports Xceed.SSH.Core

Imports Xceed.SSH.Protocols

Imports Xceed.FileSystem



Namespace DocumentationExamples.SSH

  Public Class ExecuteCommandSession1

    Public Sub Example()

      Dim host As String = "localhost"

      Dim username As String = "normal1"

      Dim password As String = "normal1"



      Dim ssh As New SSHClient()



      ' Connect to the host

      ssh.Connect(host)



      Try

        ' Log in

        ssh.Authenticate(username, password)



        ' The remote command to execute

        Dim command As String = "dir *.*"



        ' Some environment variables

        Dim environmentVariable As KeyValuePair(Of String, String) = New KeyValuePair(Of String, String)("MYVARIABLE", "MYVALUE")



        ' Create a session that will execute a remote command

        Using executeCommandSession As New ExecuteCommandSession(ssh)

          Dim commandOutputStream As Stream = Nothing

          Dim commandErrorStream As Stream = Nothing



          Try

'             We obtain the output and error streams BEFORE starting the command so that we don't

'               miss any output. 



'             If the CommandOutputStream or the CommandErrorStream object is not taken,

'               the component silently discards the incoming data. This might be desirable if

'               the output and/or error text is not needed. 



            ' Get the command's output stream (standard output)

            commandOutputStream = executeCommandSession.GetOutputStream()



            ' Get the command's error stream (standard error)

            commandErrorStream = executeCommandSession.GetErrorStream()



            ' Now that we are setup the way we want, we can safely start the remote command 



            ' Start executing the specified command on the remote server passing the supplied environment variables to the server

            executeCommandSession.Connect(command, environmentVariable)



'             Notice how we wrap the streams with StreamReader objects only after starting the command.

'               This guards against the possibility of the StreamReader object calling Stream.Read() before

'               we've started the command. 



            ' Wrap a stream reader around the output stream

            Dim outputReader As New System.IO.StreamReader(commandOutputStream)



            ' Wrap a stream reader around the error stream

            Dim errorReader As New System.IO.StreamReader(commandErrorStream)



            ' Read a line from the output and error at the same time

            Dim readOutputLineTask As Task(Of String) = outputReader.ReadLineAsync()

            Dim readErrorLineTask As Task(Of String) = errorReader.ReadLineAsync()



            Dim line As String



            ' While either the output or error streams haven't reached end-of-file

            Do While readOutputLineTask IsNot Nothing OrElse readErrorLineTask IsNot Nothing

              ' If reading an output line has completed

              If readOutputLineTask IsNot Nothing AndAlso readOutputLineTask.IsCompleted Then

                ' Get the line

                line = readOutputLineTask.Result



                ' If we have a line

                If line IsNot Nothing Then

                  ' Output it to the console

                  Console.WriteLine(line)



                  ' Read another line

                  readOutputLineTask = outputReader.ReadLineAsync()

                Else

                  ' We've reached end-of-file. We don't want to read again 

                  readOutputLineTask = Nothing

                End If

              End If



              ' If reading an error line has completed

              If readErrorLineTask IsNot Nothing AndAlso readErrorLineTask.IsCompleted Then

                ' Get the line

                line = readErrorLineTask.Result



                ' If we have a line

                If line IsNot Nothing Then

                  ' Output it to the console

                  Console.WriteLine(line)



                  ' Read another line

                  readErrorLineTask = errorReader.ReadLineAsync()

                Else

                  ' We've reached end-of-file. We don't want to read again 

                  readErrorLineTask = Nothing

                End If

              End If

            Loop



'             Because we've processed the output stream until end-of-file, we are sure that

'              the command has completed. No need to wait. 

'

'               However, if accessing the exit status or possible exit signal of the command

'               is important to the application, it is best to wait until the command has signaled it

'               has completed. At that point, the exit information will have been received. 



            ' Wait until the command has completed

            executeCommandSession.SessionCompletedWaitHandle.WaitOne()



'             Some servers will return exit information like the return code and the 'signal'

'              if the command fails. 



            Dim exitStatus As Nullable(Of Integer) = executeCommandSession.ExitStatus

            Console.WriteLine("Command exited with status {0}",If(exitStatus.HasValue, exitStatus.ToString(), "(null)"))



            Dim exitSignal As SSHChannelExitSignal = executeCommandSession.ExitSignal

            If exitSignal IsNot Nothing Then

              Console.WriteLine("Command exited with signal {0}: {1}", exitSignal.SignalName, exitSignal.ErrorMessage)

            End If

          Catch e1 As SSHChannelRequestFailedException

'             This exception is thrown by ExecuteCommandSession.Connect(). The most common

'             * cause is the authenticated user does not have the rights to execute commands

'             * on the server. 

          Finally

            If commandOutputStream IsNot Nothing Then

              commandOutputStream.Close()

              commandOutputStream = Nothing

            End If



            If commandErrorStream IsNot Nothing Then

              commandErrorStream.Close()

              commandErrorStream = Nothing

            End If

          End Try

        End Using



      Finally

        ' Always make sure to disconnect from the server when the connection is no longer needed

        ssh.Disconnect()

      End Try

    End Sub

  End Class

End Namespace

Send data to standard input

The output of the command can be captured. Here a technique using asynchronous reading is used in order to read output and error text at the same time.

C#
VB.NET

using System.IO;



using Xceed.SSH.Client;

using Xceed.SSH.Core;

using Xceed.SSH.Protocols;

using Xceed.FileSystem;



namespace DocumentationExamples.SSH

{

  public class ExecuteCommandSession2

  {

    public void Example()

    {

      string host = "localhost";

      string username = "normal1";

      string password = "normal1";



      SSHClient ssh = new SSHClient();



      // Connect to the host

      ssh.Connect( host );



      try

      {

        // Log in

        ssh.Authenticate( username, password );



        // The remote command to execute

        string command = "copy Test.txt BackTest.txt /-Y";



        // Create a session that will execute a remote command

        using( ExecuteCommandSession executeCommandSession = new ExecuteCommandSession( ssh ) )

        {

          // Get the command's output stream (standard output/stdout)

          Stream commandOutputStream = executeCommandSession.GetOutputStream();



          // Start executing the specified command on the remote server

          executeCommandSession.Connect( command );



          // Wrap the output stream into a stream reader

          System.IO.StreamReader reader = new System.IO.StreamReader( commandOutputStream );



          string line;



          /* We expect to receive the text



             Overwrite BackTest.txt? (Yes/No/All):



             and then the remote console will wait for input. We can't call ReadLine() to get

             the question since it does not contain a newline, we would wait forever.



             Since we know what we're going to receive, we'll just go-ahead and send the response immediately. */



          // Get the command's input stream (standard input/stdin)

          Stream commandInputStream = executeCommandSession.GetInputStream();



          // Wrap the input stream into a stream writer

          StreamWriter writer = new StreamWriter( commandInputStream );



          // Answer the overwrite query

          writer.WriteLine( "y" );

          writer.Flush();



          // Read the next lines until we reach end-of-file

          while( ( line = reader.ReadLine() ) != null )

          {

            // Output the line

            Console.WriteLine( line );

          }

        }

      }

      catch( SSHChannelRequestFailedException )

      {

        /* This exception is thrown by ExecuteCommandSession.Connect(). The most common

         * cause is the authenticated user does not have the rights to execute commands

         * on the server. */

        }

      finally

      {

        // Always make sure to disconnect from the server when the connection is no longer needed

        ssh.Disconnect();

      }

    }

  }

}

Imports System.IO



Imports Xceed.SSH.Client

Imports Xceed.SSH.Core

Imports Xceed.SSH.Protocols

Imports Xceed.FileSystem



Namespace DocumentationExamples.SSH

  Public Class ExecuteCommandSession2

    Public Sub Example()

      Dim host As String = "localhost"

      Dim username As String = "normal1"

      Dim password As String = "normal1"



      Dim ssh As New SSHClient()



      ' Connect to the host

      ssh.Connect(host)



      Try

        ' Log in

        ssh.Authenticate(username, password)



        ' The remote command to execute

        Dim command As String = "copy Test.txt BackTest.txt /-Y"



        ' Create a session that will execute a remote command

        Using executeCommandSession As New ExecuteCommandSession(ssh)

          ' Get the command's output stream (standard output/stdout)

          Dim commandOutputStream As Stream = executeCommandSession.GetOutputStream()



          ' Start executing the specified command on the remote server

          executeCommandSession.Connect(command)



          ' Wrap the output stream into a stream reader

          Dim reader As New System.IO.StreamReader(commandOutputStream)



          Dim line As String



'           We expect to receive the text

'

'             Overwrite BackTest.txt? (Yes/No/All):

'

'             and then the remote console will wait for input. We can't call ReadLine() to get

'             the question since it does not contain a newline, we would wait forever.

'

'             Since we know what we're going to receive, we'll just go-ahead and send the response immediately. 



          ' Get the command's input stream (standard input/stdin)

          Dim commandInputStream As Stream = executeCommandSession.GetInputStream()



          ' Wrap the input stream into a stream writer

          Dim writer As New StreamWriter(commandInputStream)



          ' Answer the overwrite query

          writer.WriteLine("y")

          writer.Flush()



          ' Read the next lines until we reach end-of-file

          line = reader.ReadLine()

          Do While line IsNot Nothing

            ' Output the line

            Console.WriteLine(line)

            line = reader.ReadLine()

          Loop

        End Using

      Catch e1 As SSHChannelRequestFailedException

'         This exception is thrown by ExecuteCommandSession.Connect(). The most common

'         * cause is the authenticated user does not have the rights to execute commands

'         * on the server. 

      Finally

        ' Always make sure to disconnect from the server when the connection is no longer needed

        ssh.Disconnect()

      End Try

    End Sub

  End Class

End Namespace