Delphi DLL

Release an SSH Channel's Local Resources

Demonstrates the Chilkat Ssh.ChannelRelease method, which releases Chilkat's retained local resources for a channel after all output and exit information has been retrieved. The only argument is the channel number.

Background: Chilkat retains a channel's buffered output and exit information after the channel closes, so you can still read a command's final output. That retention costs memory, and a long-running program that opens many channels should release each one when finished with it. Note this is not a channel-closing method — it sends neither EOF nor CLOSE. Retrieve everything you need first, because releasing discards it.

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var
success: Boolean;
ssh: HCkSsh;
sshPort: Integer;
password: PWideChar;
channelNum: Integer;
output: PWideChar;

begin
success := False;

//  Demonstrates the Ssh.ChannelRelease method, which releases Chilkat's retained local resources
//  for a channel after all output and exit information has been retrieved.  The only argument is
//  the channel number.

ssh := CkSsh_Create();

sshPort := 22;
success := CkSsh_Connect(ssh,'ssh.example.com',sshPort);
if (success = False) then
  begin
    Memo1.Lines.Add(CkSsh__lastErrorText(ssh));
    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 := CkSsh_AuthenticatePw(ssh,'mySshLogin',password);
if (success = False) then
  begin
    Memo1.Lines.Add(CkSsh__lastErrorText(ssh));
    Exit;
  end;

//  Open a session channel.  A negative return value indicates failure.
channelNum := CkSsh_OpenSessionChannel(ssh);
if (channelNum < 0) then
  begin
    Memo1.Lines.Add(CkSsh__lastErrorText(ssh));
    Exit;
  end;

success := CkSsh_SendReqExec(ssh,channelNum,'uname -a');
if (success = False) then
  begin
    Memo1.Lines.Add(CkSsh__lastErrorText(ssh));
    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.
CkSsh_putReadTimeoutMs(ssh,15000);

//  Retrieve everything of interest before releasing the channel.
success := CkSsh_ChannelReceiveToClose(ssh,channelNum);
if (success = False) then
  begin
    Memo1.Lines.Add(CkSsh__lastErrorText(ssh));
    Exit;
  end;

output := CkSsh__getReceivedText(ssh,channelNum,'utf-8');
if (CkSsh_getLastMethodSuccess(ssh) = False) then
  begin
    Memo1.Lines.Add(CkSsh__lastErrorText(ssh));
    Exit;
  end;
Memo1.Lines.Add(output);

//  Release the retained local resources.  This does not send EOF or CLOSE.
CkSsh_ChannelRelease(ssh,channelNum);

CkSsh_Disconnect(ssh);

CkSsh_Dispose(ssh);