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Read Data from an SSH Channel

Demonstrates the Chilkat Ssh.ChannelRead method, which reads incoming SSH channel messages. The only argument is the channel number; the ReadTimeoutMs property limits how long it waits. Received data is appended to the channel's receive buffer, then retrieved with a GetReceived... method.

The integer return value is -1 on error, -2 if nothing arrived before the timeout, 0 if EOF or channel close was processed, or — when greater than 0 — the total bytes currently buffered for the channel (not the bytes newly received by this call).

Background: SSH reading is a two-step pattern that trips people up at first: the Channel* read/poll methods move bytes from the network into an internal per-channel buffer, and a separate GetReceived... call hands that buffer to your code. A positive return is therefore a buffer total, not a count of what this call fetched. Note that a 0 return means EOF or close — buffered data can still remain and should be drained.

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Local $bSuccess = False

;  Demonstrates the Ssh.ChannelRead method, which reads incoming SSH channel messages.  The only
;  argument is the channel number.  The ReadTimeoutMs property limits how long it waits.

$oSsh = ObjCreate("Chilkat.Ssh")

Local $iSshPort = 22
$bSuccess = $oSsh.Connect("ssh.example.com",$iSshPort)
If ($bSuccess = False) Then
    ConsoleWrite($oSsh.LastErrorText & @CRLF)
    Exit
EndIf

;  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.
Local $sPassword = "mySshPassword"

$bSuccess = $oSsh.AuthenticatePw("mySshLogin",$sPassword)
If ($bSuccess = False) Then
    ConsoleWrite($oSsh.LastErrorText & @CRLF)
    Exit
EndIf

Local $iChannelNum = $oSsh.OpenSessionChannel()
If ($iChannelNum < 0) Then
    ConsoleWrite($oSsh.LastErrorText & @CRLF)
    Exit
EndIf

;  Start a shell WITHOUT requesting a PTY.  Without a PTY the shell sees it is connected to a
;  raw data pipe and enters non-interactive mode: it suppresses the command prompt, does not
;  echo typed commands back, and skips interactive login scripts.  The output is therefore
;  clean and easily parseable -- but because no prompt is ever sent, code must not wait for
;  one.  Instead, have each command print a predictable marker, or wait for EOF / channel close.
$bSuccess = $oSsh.SendReqShell($iChannelNum)
If ($bSuccess = False) Then
    ConsoleWrite($oSsh.LastErrorText & @CRLF)
    Exit
EndIf

$bSuccess = $oSsh.ChannelSendString($iChannelNum,"uname -a" & @LF,"utf-8")
If ($bSuccess = False) Then
    ConsoleWrite($oSsh.LastErrorText & @CRLF)
    Exit
EndIf

;  The return value is: -1 on error, -2 if nothing arrived before the timeout, 0 if EOF or
;  channel close was processed, or the total number of buffered bytes when greater than 0.
Local $iResult = $oSsh.ChannelRead($iChannelNum)
If ($iResult = -1) Then
    ConsoleWrite($oSsh.LastErrorText & @CRLF)
    Exit
EndIf

If ($iResult = -2) Then
    ConsoleWrite("No channel data arrived before the timeout." & @CRLF)
EndIf

If ($iResult = 0) Then
    ConsoleWrite("EOF or channel close was processed.  Buffered data may still remain." & @CRLF)
EndIf

If ($iResult > 0) Then
    ConsoleWrite("Total bytes buffered: " & $iResult & @CRLF)
EndIf

Local $sOutput = $oSsh.GetReceivedText($iChannelNum,"utf-8")
If ($oSsh.LastMethodSuccess = False) Then
    ConsoleWrite($oSsh.LastErrorText & @CRLF)
    Exit
EndIf

ConsoleWrite($sOutput & @CRLF)

$oSsh.Disconnect