Delphi DLL

Multiple SendReqExec on the Same Connection

Demonstrates running a series of commands on one SSH connection using SendReqExec. Each exec request requires its own logical channel — this is not a separate SSH connection, just a new session channel on the existing one.

Background: An SSH session channel is single-use for an exec request: once the command runs and the server closes the channel, that channel cannot be reused. Opening a fresh channel per command is cheap, since the expensive work — the TCP connection, key exchange, and authentication — is done once and shared. This is why running ten commands over one connection is far faster than connecting ten times.

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var
success: Boolean;
ssh: HCkSsh;
hostname: PWideChar;
port: Integer;
password: PWideChar;
channelNum: Integer;
cmdOutput: PWideChar;

begin
success := False;

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

//  Demonstrates running a series of commands on one SSH connection using SendReqExec.  Each exec
//  request requires its own logical channel.  This is not a new SSH connection -- it is simply a
//  new session channel on the existing one.

ssh := CkSsh_Create();

hostname := 'ssh.example.com';
port := 22;
success := CkSsh_Connect(ssh,hostname,port);
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;

//  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);

//  ---- 1st command, on its own session channel ----
channelNum := CkSsh_OpenSessionChannel(ssh);
if (channelNum < 0) then
  begin
    Memo1.Lines.Add(CkSsh__lastErrorText(ssh));
    Exit;
  end;

success := CkSsh_SendReqExec(ssh,channelNum,'ls -al');
if (success = False) then
  begin
    Memo1.Lines.Add(CkSsh__lastErrorText(ssh));
    Exit;
  end;

success := CkSsh_ChannelReceiveToClose(ssh,channelNum);
if (success = False) then
  begin
    Memo1.Lines.Add(CkSsh__lastErrorText(ssh));
    Exit;
  end;

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

//  ---- 2nd command, on a NEW session channel over the same connection ----
channelNum := CkSsh_OpenSessionChannel(ssh);
if (channelNum < 0) then
  begin
    Memo1.Lines.Add(CkSsh__lastErrorText(ssh));
    Exit;
  end;

success := CkSsh_SendReqExec(ssh,channelNum,'nslookup chilkatsoft.com');
if (success = False) then
  begin
    Memo1.Lines.Add(CkSsh__lastErrorText(ssh));
    Exit;
  end;

success := CkSsh_ChannelReceiveToClose(ssh,channelNum);
if (success = False) then
  begin
    Memo1.Lines.Add(CkSsh__lastErrorText(ssh));
    Exit;
  end;

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

CkSsh_Disconnect(ssh);

CkSsh_Dispose(ssh);