Xojo Plugin

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.

Chilkat Xojo Plugin Downloads

Download Chilkat for Xojo Plugin

Xojo Plugin

Dim success As Boolean
success = False

//  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 Chilkat.Ssh

Dim port As Int32
port = 22
success = ssh.Connect("ssh.example.com",port)
If (success = False) Then
    System.DebugLog(ssh.LastErrorText)
    Return
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 = False) Then
    System.DebugLog(ssh.LastErrorText)
    Return
End If

//  QuickCmdSend starts a command and returns immediately, so all three run concurrently, each on
//  its own session channel.
Dim channel1 As Int32
channel1 = ssh.QuickCmdSend("df")
If (channel1 < 0) Then
    System.DebugLog(ssh.LastErrorText)
    Return
End If

Dim channel2 As Int32
channel2 = ssh.QuickCmdSend("date")
If (channel2 < 0) Then
    System.DebugLog(ssh.LastErrorText)
    Return
End If

Dim channel3 As Int32
channel3 = ssh.QuickCmdSend("echo hello world")
If (channel3 < 0) Then
    System.DebugLog(ssh.LastErrorText)
    Return
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 Int32
pollTimeoutMs = 50
Dim numFinished As Int32
numFinished = 0
While numFinished < 3
    Dim channel As Int32
    channel = ssh.QuickCmdCheck(pollTimeoutMs)
    If (channel = -2) Then
        System.DebugLog(ssh.LastErrorText)
        Return
    End If

    If (channel >= 0) Then
        System.DebugLog("---- channel " + Str(channel) + " finished ----")
        Dim cmdOutput As String
        cmdOutput = ssh.GetReceivedText(channel,"utf-8")
        If (ssh.LastMethodSuccess = False) Then
            System.DebugLog(ssh.LastErrorText)
            Return
        End If

        System.DebugLog(cmdOutput)
        numFinished = numFinished + 1
    End If

Wend

ssh.Disconnect