Delphi ActiveX

Check Whether SSH Channel CLOSE Was Received

Demonstrates the Chilkat Ssh.ChannelReceivedClose method, which reports whether an SSH CLOSE message has been received for a channel. The only argument is the channel number. Remote CLOSE is distinct from EOF and closes the channel in both directions.

Background: Remote CLOSE is the definitive end of a channel's life. Once it is processed, ChannelIsOpen becomes false and the channel is normally removed from NumOpenChannels. Checking it distinguishes "the server finished sending output" (EOF) from "the channel is fully finished" (CLOSE) — which is what you want before concluding a remote command has completely wrapped up.

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var
success: Integer;
ssh: TChilkatSsh;
sshPort: Integer;
password: WideString;
channelNum: Integer;

begin
success := 0;

//  Demonstrates the Ssh.ChannelReceivedClose method, which reports whether an SSH CLOSE message
//  has been received for a channel.  The only argument is the channel number.  Remote CLOSE is
//  distinct from EOF and closes the channel in both directions.

ssh := TChilkatSsh.Create(Self);

sshPort := 22;
success := ssh.Connect('ssh.example.com',sshPort);
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;

channelNum := ssh.OpenSessionChannel();
if (channelNum < 0) then
  begin
    Memo1.Lines.Add(ssh.LastErrorText);
    Exit;
  end;

success := ssh.SendReqExec(channelNum,'ls -l /tmp');
if (success = 0) then
  begin
    Memo1.Lines.Add(ssh.LastErrorText);
    Exit;
  end;

//  IMPORTANT: Set a read timeout.  ReadTimeoutMs defaults to 0, which means no limit -- without
//  it, this call waits forever if the server never sends channel close.
ssh.ReadTimeoutMs := 15000;

success := ssh.ChannelReceiveToClose(channelNum);
if (success = 0) then
  begin
    Memo1.Lines.Add(ssh.LastErrorText);
    Exit;
  end;

//  The server may send EOF before CLOSE.  During that interval EOF is 1 while CLOSE is
//  still 0.
if (ssh.ChannelReceivedEof(channelNum)) then
  begin
    Memo1.Lines.Add('EOF received.');
  end;

if (ssh.ChannelReceivedClose(channelNum)) then
  begin
    Memo1.Lines.Add('Remote CLOSE received -- the channel is closed in both directions.');
  end
else
  begin
    Memo1.Lines.Add('No remote CLOSE received.');
  end;

ssh.Disconnect();