Delphi ActiveX

SSH Commands to a Cisco Switch

Demonstrates establishing an SSH session with a Cisco switch (or similar device) and sending commands in a device console session. Each command is sent, and its output is read up to the device's next prompt.

Note: QuickShell allocates a PTY, which is what a network device console expects. The device presents an interactive prompt, and each command's output is read up to the next prompt.

Background: Network devices differ from general-purpose servers in that they expose a menu- or prompt-driven console rather than a Unix shell, so exec requests are usually unavailable and driving the interactive console is the only option. That makes prompt matching the synchronization mechanism, and it is why a PTY is appropriate here despite the general advice to avoid one. Retrieving the received text between commands is essential: a prompt left in the buffer would make the next receive return immediately with the wrong output.

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var
success: Integer;
ssh: TChilkatSsh;
port: Integer;
password: WideString;
channelNum: Integer;
caseSensitive: Integer;
cmdOutput: WideString;

begin
success := 0;

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

//  Demonstrates establishing an SSH session with a Cisco switch (or similar device) and sending
//  commands in a device console session.
//  
//  Note: QuickShell allocates a PTY, which is what a network device console expects.  The device
//  presents an interactive prompt, and each command's output is read up to the next prompt.

ssh := TChilkatSsh.Create(Self);

port := 22;
success := ssh.Connect('172.16.16.100',port);
if (success = 0) then
  begin
    Memo1.Lines.Add(ssh.LastErrorText);
    Exit;
  end;

//  Normally you would not hard-code the password in source.  You should instead obtain it
//  from an interactive prompt, environment variable, or a secrets vault.
password := 'mySshPassword';

success := ssh.AuthenticatePw('mySshLogin',password);
if (success = 0) then
  begin
    Memo1.Lines.Add(ssh.LastErrorText);
    Exit;
  end;

//  Start a shell session.
channelNum := ssh.QuickShell();
if (channelNum < 0) then
  begin
    Memo1.Lines.Add(ssh.LastErrorText);
    Exit;
  end;

//  IMPORTANT: Set a read timeout before receiving until a match.  ReadTimeoutMs defaults to 0,
//  which means no limit -- without it, this call waits forever if the received data never
//  contains a match.
ssh.ReadTimeoutMs := 15000;

caseSensitive := 1;

//  The switch presents a prompt ending in "#".  Reading up to it confirms the session is ready.
success := ssh.ChannelReceiveUntilMatch(channelNum,'#','utf-8',caseSensitive);
if (success = 0) then
  begin
    Memo1.Lines.Add(ssh.LastErrorText);
    Exit;
  end;

cmdOutput := ssh.GetReceivedText(channelNum,'utf-8');
if (ssh.LastMethodSuccess = 0) then
  begin
    Memo1.Lines.Add(ssh.LastErrorText);
    Exit;
  end;
Memo1.Lines.Add(cmdOutput);

//  Send a command and read its output up to the next prompt.
success := ssh.ChannelSendString(channelNum,'show clock' + #10,'utf-8');
if (success = 0) then
  begin
    Memo1.Lines.Add(ssh.LastErrorText);
    Exit;
  end;

success := ssh.ChannelReceiveUntilMatch(channelNum,'#','utf-8',caseSensitive);
if (success = 0) then
  begin
    Memo1.Lines.Add(ssh.LastErrorText);
    Exit;
  end;

//  Retrieving the text also clears the receive buffer, which matters: if the prompt were left
//  buffered, the next receive would match it immediately and return the wrong output.
cmdOutput := ssh.GetReceivedText(channelNum,'utf-8');
if (ssh.LastMethodSuccess = 0) then
  begin
    Memo1.Lines.Add(ssh.LastErrorText);
    Exit;
  end;
Memo1.Lines.Add(cmdOutput);

//  Additional commands follow the same send / read-to-prompt / retrieve pattern.
success := ssh.ChannelSendString(channelNum,'show version' + #10,'utf-8');
if (success = 0) then
  begin
    Memo1.Lines.Add(ssh.LastErrorText);
    Exit;
  end;

success := ssh.ChannelReceiveUntilMatch(channelNum,'#','utf-8',caseSensitive);
if (success = 0) then
  begin
    Memo1.Lines.Add(ssh.LastErrorText);
    Exit;
  end;

cmdOutput := ssh.GetReceivedText(channelNum,'utf-8');
if (ssh.LastMethodSuccess = 0) then
  begin
    Memo1.Lines.Add(ssh.LastErrorText);
    Exit;
  end;
Memo1.Lines.Add(cmdOutput);

ssh.Disconnect();