Read an SSH Channel Until Output Goes Quiet

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Demonstrates the Chilkat Ssh.ChannelReadAndPoll method, which reads a channel in two phases: it waits for the first channel message, then keeps processing until no further data arrives for the given number of milliseconds. The first argument is the channel number and the second is the second-phase poll timeout.

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).

Dim success As Long
success = 0

'  Demonstrates the Ssh.ChannelReadAndPoll method, which reads a channel in two phases: it waits
'  for the first channel message, then keeps processing until no more data arrives for the given
'  number of milliseconds.  The 1st argument is the channel number and the 2nd is the poll
'  timeout for the second phase.

Dim ssh As New ChilkatSsh

Dim sshPort As Long
sshPort = 22
success = ssh.Connect("ssh.example.com",sshPort)
If (success = 0) Then
    Debug.Print ssh.LastErrorText
    Exit Sub
End If

'  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.
Dim password As String
password = "mySshPassword"

success = ssh.AuthenticatePw("mySshLogin",password)
If (success = 0) Then
    Debug.Print ssh.LastErrorText
    Exit Sub
End If

Dim channelNum As Long
channelNum = ssh.OpenSessionChannel()
If (channelNum < 0) Then
    Debug.Print ssh.LastErrorText
    Exit Sub
End If

'  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.
success = ssh.SendReqShell(channelNum)
If (success = 0) Then
    Debug.Print ssh.LastErrorText
    Exit Sub
End If

success = ssh.ChannelSendString(channelNum,"ls -l /usr/bin" & vbLf,"utf-8")
If (success = 0) Then
    Debug.Print ssh.LastErrorText
    Exit Sub
End If

'  Keep reading until the output goes quiet for 500 milliseconds.
Dim pollTimeoutMs As Long
pollTimeoutMs = 500
'  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.
Dim result As Long
result = ssh.ChannelReadAndPoll(channelNum,pollTimeoutMs)
If (result = -1) Then
    Debug.Print ssh.LastErrorText
    Exit Sub
End If

If (result = -2) Then
    Debug.Print "No channel data arrived before the timeout."
End If

If (result = 0) Then
    Debug.Print "EOF or channel close was processed.  Buffered data may still remain."
End If

If (result > 0) Then
    Debug.Print "Total bytes buffered: " & result
End If

Dim output As String
output = ssh.GetReceivedText(channelNum,"utf-8")
If (ssh.LastMethodSuccess = 0) Then
    Debug.Print ssh.LastErrorText
    Exit Sub
End If

Debug.Print output

ssh.Disconnect