Visual Basic 6.0

SSH Parallel Remote Commands on Multiple Servers

Demonstrates running the same command on several servers simultaneously. It is simply a matter of using one Ssh object per server, starting the command on each with QuickCmdSend, and then polling each connection with QuickCmdCheck until all have finished.

Background: This is the fan-out pattern behind configuration-management and monitoring tools: query or update a whole fleet in roughly the time the slowest single host takes, rather than the sum of all of them. Each server needs its own object because each has its own connection and authentication state. Note that results come back in whatever order the servers finish, which is why the example tracks completion per connection. Production code would keep the objects in arrays instead of repeating the logic per server.

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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 the same command on several servers simultaneously.  It is simply a
'  matter of using one Ssh object per server.

Dim ssh1 As New ChilkatSsh
Dim ssh2 As New ChilkatSsh
Dim ssh3 As New ChilkatSsh

Dim port As Long
port = 22

'  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 = ssh1.Connect("ssh-server1.example.com",port)
If (success = 0) Then
    Debug.Print ssh1.LastErrorText
    Exit Sub
End If

success = ssh1.AuthenticatePw("mySshLogin",password)
If (success = 0) Then
    Debug.Print ssh1.LastErrorText
    Exit Sub
End If

success = ssh2.Connect("ssh-server2.example.com",port)
If (success = 0) Then
    Debug.Print ssh2.LastErrorText
    Exit Sub
End If

success = ssh2.AuthenticatePw("mySshLogin",password)
If (success = 0) Then
    Debug.Print ssh2.LastErrorText
    Exit Sub
End If

success = ssh3.Connect("ssh-server3.example.com",port)
If (success = 0) Then
    Debug.Print ssh3.LastErrorText
    Exit Sub
End If

success = ssh3.AuthenticatePw("mySshLogin",password)
If (success = 0) Then
    Debug.Print ssh3.LastErrorText
    Exit Sub
End If

'  This command sleeps for 5 seconds and then prints the system date/time, making the parallel
'  execution easy to observe.
Dim cmd As String
cmd = "sleep 5; date"

'  Start the command on each server.  QuickCmdSend returns immediately.
Dim channel1 As Long
channel1 = ssh1.QuickCmdSend(cmd)
If (channel1 < 0) Then
    Debug.Print ssh1.LastErrorText
    Exit Sub
End If

Dim channel2 As Long
channel2 = ssh2.QuickCmdSend(cmd)
If (channel2 < 0) Then
    Debug.Print ssh2.LastErrorText
    Exit Sub
End If

Dim channel3 As Long
channel3 = ssh3.QuickCmdSend(cmd)
If (channel3 < 0) Then
    Debug.Print ssh3.LastErrorText
    Exit Sub
End If

'  The command is now running on all three servers at once.  Poll each connection until every
'  command has finished.  (Production code would keep the objects in arrays rather than
'  repeating the logic.)
Dim pollTimeoutMs As Long
pollTimeoutMs = 50
Dim numFinished As Long
numFinished = 0
Dim finished1 As Long
finished1 = 0
Dim finished2 As Long
finished2 = 0
Dim finished3 As Long
finished3 = 0

Do While numFinished < 3
    If (Not finished1) Then
        Dim ch1 As Long
        ch1 = ssh1.QuickCmdCheck(pollTimeoutMs)
        If (ch1 = -2) Then
            Debug.Print ssh1.LastErrorText
            Exit Sub
        End If

        If (ch1 >= 0) Then
            Debug.Print "---- ssh1 channel " & ch1 & " finished ----"
            Dim out1 As String
            out1 = ssh1.GetReceivedText(ch1,"utf-8")
            If (ssh1.LastMethodSuccess = 0) Then
                Debug.Print ssh1.LastErrorText
                Exit Sub
            End If

            Debug.Print out1
            finished1 = 1
            numFinished = numFinished + 1
        End If

    End If

    If (Not finished2) Then
        Dim ch2 As Long
        ch2 = ssh2.QuickCmdCheck(pollTimeoutMs)
        If (ch2 = -2) Then
            Debug.Print ssh2.LastErrorText
            Exit Sub
        End If

        If (ch2 >= 0) Then
            Debug.Print "---- ssh2 channel " & ch2 & " finished ----"
            Dim out2 As String
            out2 = ssh2.GetReceivedText(ch2,"utf-8")
            If (ssh2.LastMethodSuccess = 0) Then
                Debug.Print ssh2.LastErrorText
                Exit Sub
            End If

            Debug.Print out2
            finished2 = 1
            numFinished = numFinished + 1
        End If

    End If

    If (Not finished3) Then
        Dim ch3 As Long
        ch3 = ssh3.QuickCmdCheck(pollTimeoutMs)
        If (ch3 = -2) Then
            Debug.Print ssh3.LastErrorText
            Exit Sub
        End If

        If (ch3 >= 0) Then
            Debug.Print "---- ssh3 channel " & ch3 & " finished ----"
            Dim out3 As String
            out3 = ssh3.GetReceivedText(ch3,"utf-8")
            If (ssh3.LastMethodSuccess = 0) Then
                Debug.Print ssh3.LastErrorText
                Exit Sub
            End If

            Debug.Print out3
            finished3 = 1
            numFinished = numFinished + 1
        End If

    End If

Loop

ssh1.Disconnect 
ssh2.Disconnect 
ssh3.Disconnect