Pascal (Lazarus/Delphi)

TCP Socket through SSH Tunnel (Port Forwarding)

See more Socket/SSL/TLS Examples

Demonstrates using Chilkat Socket to communicate to a TCP service through an SSH tunnel. This example will connect to an NIST time server and (using the old Time Protocol (RFC 868)), will read the current GMT time.

Note: This is not necessarily a recommended means for getting the current date/time. The most commonly used time protocol is the Network Time Protocol (RFC-1305). The intent of this example is to show how TCP communications can occur through an SSH tunnel.

Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.CkDateTime,
  Chilkat.Socket;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  tunnel: TSocket;
  sshHostname: string;
  sshPort: Integer;
  maxWaitMs: Integer;
  useTls: Boolean;
  channel: TSocket;
  bigEndian: Boolean;
  dt: TCkDateTime;
  bLocalTime: Boolean;

begin
  success := False;

  //  This example requires the Chilkat API to have been previously unlocked.
  //  See Global Unlock Sample for sample code.

  tunnel := TSocket.Create;

  sshHostname := 'sftp.example.com';
  sshPort := 22;

  //  Connect to an SSH server and establish the SSH tunnel:
  success := tunnel.SshOpenTunnel(sshHostname,sshPort);
  if (success = False) then
    begin
      WriteLn(tunnel.LastErrorText);
      Exit;
    end;

  //  Authenticate with the SSH server via a login/password
  //  or with a public key.
  //  This example demonstrates SSH password authentication.
  success := tunnel.SshAuthenticatePw('mySshLogin','mySshPassword');
  if (success = False) then
    begin
      WriteLn(tunnel.LastErrorText);
      Exit;
    end;

  //  OK, the SSH tunnel is setup.  Now open a channel within the tunnel.
  //  Once the channel is obtained, the Socket API may
  //  be used exactly the same as usual, except all communications
  //  are sent through the channel in the SSH tunnel.
  //  Any number of channels may be created from the same SSH tunnel.
  //  Multiple channels may coexist at the same time.

  //  Connect to an NIST time server and read the current date/time
  maxWaitMs := 4000;
  useTls := False;
  channel := TSocket.Create;
  success := tunnel.SshNewChannel('time-c.nist.gov',37,useTls,maxWaitMs,channel);
  if (success = False) then
    begin
      WriteLn(tunnel.LastErrorText);
      Exit;
    end;

  //  The time server will send a big-endian 32-bit integer representing
  //  the number of seconds since since 00:00 (midnight) 1 January 1900 GMT.
  //  The ReceiveInt32 method will receive a 4-byte integer, but returns
  //  True or False to indicate success.  If successful, the integer
  //  is obtained via the ReceivedInt property.
  bigEndian := True;
  success := channel.ReceiveInt32(bigEndian);
  if (success = False) then
    begin
      WriteLn(channel.LastErrorText);
      Exit;
    end;

  dt := TCkDateTime.Create;
  dt.SetFromNtpTime(channel.ReceivedInt);

  //  Show the current local date/time
  bLocalTime := True;
  WriteLn('Current local date/time: ' + dt.GetAsRfc822(bLocalTime));

  //  Close the SSH channel.
  success := channel.Close(maxWaitMs);
  if (success <> True) then
    begin
      WriteLn(channel.LastErrorText);
      Exit;
    end;

  //  It is possible to create a new channel from the existing SSH tunnel for the next connection:
  //  Any number of channels may be created from the same SSH tunnel.
  //  Multiple channels may coexist at the same time.
  success := tunnel.SshNewChannel('time-a.nist.gov',37,useTls,maxWaitMs,channel);
  if (success = False) then
    begin
      WriteLn(tunnel.LastErrorText);
      Exit;
    end;

  //  Review the LastErrorText to see that the connection was made via the SSH tunnel:
  WriteLn(tunnel.LastErrorText);

  //  Close the connection to time-a.nist.gov.  This is actually closing our channel
  //  within the SSH tunnel, but keeps the tunnel open for the next port-forwarded connection.
  success := channel.Close(maxWaitMs);
  if (success <> True) then
    begin
      WriteLn(channel.LastErrorText);
      Exit;
    end;

  //  Finally, close the SSH tunnel.
  success := tunnel.SshCloseTunnel();
  if (success = False) then
    begin
      WriteLn(tunnel.LastErrorText);
      Exit;
    end;

  WriteLn('TCP SSH tunneling example completed.');


  tunnel.Free;
  channel.Free;
  dt.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.