VB.NET

Start Concurrent SSH Commands with QuickCmdSend

Demonstrates the Chilkat Ssh.QuickCmdSend method, which starts a remote command and immediately returns its channel number. The only argument is the command line. Internally it opens a session channel and sends an exec request.

Background: Because it returns without waiting, several commands can run concurrently over one authenticated connection — far faster than running them one after another when each has latency or slow work to do. Pair it with QuickCmdCheck, which reports commands as they finish, so results can be collected in completion order rather than the order they were started.

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Dim success As Boolean = False

'  Demonstrates the Ssh.QuickCmdSend method, which starts a remote command and immediately
'  returns its channel number.  The only argument is the command line.  Because it returns
'  right away, several commands can run concurrently on the same SSH connection.

Dim ssh As New Chilkat.Ssh

Dim sshPort As Integer = 22
success = ssh.Connect("ssh.example.com",sshPort)
If (success = False) Then
    Debug.WriteLine(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 = "mySshPassword"

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


'  Start three commands without waiting for any of them to finish.
Dim channel1 As Integer = ssh.QuickCmdSend("sleep 2; echo first done")
If (channel1 < 0) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


Dim channel2 As Integer = ssh.QuickCmdSend("echo second done")
If (channel2 < 0) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


Dim channel3 As Integer = ssh.QuickCmdSend("sleep 1; echo third done")
If (channel3 < 0) Then
    Debug.WriteLine(ssh.LastErrorText)
    Exit Sub
End If


Debug.WriteLine("Started three concurrent commands.")

'  Use QuickCmdCheck to collect the results as each command completes.

ssh.Disconnect()