Visual Basic 6.0

SSH Parallel Remote Commands on a Single Server

Demonstrates running several commands in parallel on one SSH server and collecting each command's output as it finishes. QuickCmdSend starts each command and returns immediately; QuickCmdCheck reports them as they complete.

Background: Because SSH multiplexes channels, several commands can run at once over one authenticated connection — far faster than running them one after another when each involves waiting. Results arrive in completion order rather than the order the commands were started, so the loop keys off the returned channel number. Distinguish the two negative returns carefully: -1 means "still working, ask again," while -2 means nothing remains to collect or the connection failed.

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Visual Basic 6.0

Dim success As Long
success = 0

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

'  Demonstrates running several commands in parallel on a single SSH server and collecting each
'  command's output as it finishes.

Dim ssh As New ChilkatSsh

Dim port As Long
port = 22
success = ssh.Connect("ssh.example.com",port)
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

'  QuickCmdSend starts a command and returns immediately, so all three run concurrently, each on
'  its own session channel.
Dim channel1 As Long
channel1 = ssh.QuickCmdSend("df")
If (channel1 < 0) Then
    Debug.Print ssh.LastErrorText
    Exit Sub
End If

Dim channel2 As Long
channel2 = ssh.QuickCmdSend("date")
If (channel2 < 0) Then
    Debug.Print ssh.LastErrorText
    Exit Sub
End If

Dim channel3 As Long
channel3 = ssh.QuickCmdSend("echo hello world")
If (channel3 < 0) Then
    Debug.Print ssh.LastErrorText
    Exit Sub
End If

'  Collect the results.  QuickCmdCheck returns the channel number of a completed command,
'  -1 when commands are still pending but none finished within the timeout, or -2 when nothing
'  remains to be checked (or an error occurred).
Dim pollTimeoutMs As Long
pollTimeoutMs = 50
Dim numFinished As Long
numFinished = 0
Do While numFinished < 3
    Dim channel As Long
    channel = ssh.QuickCmdCheck(pollTimeoutMs)
    If (channel = -2) Then
        Debug.Print ssh.LastErrorText
        Exit Sub
    End If

    If (channel >= 0) Then
        Debug.Print "---- channel " & channel & " finished ----"
        Dim cmdOutput As String
        cmdOutput = ssh.GetReceivedText(channel,"utf-8")
        If (ssh.LastMethodSuccess = 0) Then
            Debug.Print ssh.LastErrorText
            Exit Sub
        End If

        Debug.Print cmdOutput
        numFinished = numFinished + 1
    End If

Loop

ssh.Disconnect