Delphi ActiveX

Wait for a Message on Any SSH Channel

Demonstrates the Chilkat Ssh.WaitForChannelMessage method, which waits for the next SSH channel message on any channel. The only argument is the poll timeout: 0 for a nonblocking check, a positive value to wait that long, or a negative value to wait with no method-level timeout. It returns the channel number the message belongs to, -1 if nothing arrived before the timeout, or -2 on another error such as a lost connection.

Background: When several channels are active at once, waiting on one specific channel would block while others sit ready. This method is the multiplexed alternative — it returns as soon as any channel has activity and tells you which one, so a single loop can service them all. The explicit timeout argument governs the wait; shorter ReadTimeoutMs values do not cut it short.

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

begin
success := 0;

//  Demonstrates the Ssh.WaitForChannelMessage method, which waits for the next SSH channel
//  message on ANY channel.  The only argument is the poll timeout in milliseconds: 0 for a
//  nonblocking check, a positive value to wait that long, or a negative value to wait with no
//  method-level timeout.

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;

//  Wait up to 5 seconds for the next channel message.  The return value is the channel number
//  the message belongs to, -1 if nothing arrived before the timeout, or -2 on another error.
pollTimeoutMs := 5000;
result := ssh.WaitForChannelMessage(pollTimeoutMs);

if (result = -2) then
  begin
    Memo1.Lines.Add(ssh.LastErrorText);
    Exit;
  end;

if (result = -1) then
  begin
    Memo1.Lines.Add('No channel message arrived before the timeout.');
  end;

if (result >= 0) then
  begin
    Memo1.Lines.Add('Processed a message for channel ' + IntToStr(result));
  end;

ssh.Disconnect();