Xojo Plugin

Wait for a Message on Any SSH Channel

Demonstrates the Chilkat Ssh.WaitForChannelMessage method, which waits for the next SSH channel message on any channel. The only argument is the poll timeout: 0 for a nonblocking check, a positive value to wait that long, or a negative value to wait with no method-level timeout. It returns the channel number the message belongs to, -1 if nothing arrived before the timeout, or -2 on another error such as a lost connection.

Background: When several channels are active at once, waiting on one specific channel would block while others sit ready. This method is the multiplexed alternative — it returns as soon as any channel has activity and tells you which one, so a single loop can service them all. The explicit timeout argument governs the wait; shorter ReadTimeoutMs values do not cut it short.

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Dim success As Boolean
success = False

//  Demonstrates the Ssh.WaitForChannelMessage method, which waits for the next SSH channel
//  message on ANY channel.  The only argument is the poll timeout in milliseconds: 0 for a
//  nonblocking check, a positive value to wait that long, or a negative value to wait with no
//  method-level timeout.

Dim ssh As New Chilkat.Ssh

Dim sshPort As Int32
sshPort = 22
success = ssh.Connect("ssh.example.com",sshPort)
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

Dim channelNum As Int32
channelNum = ssh.OpenSessionChannel()
If (channelNum < 0) Then
    System.DebugLog(ssh.LastErrorText)
    Return
End If

success = ssh.SendReqExec(channelNum,"ls -l /tmp")
If (success = False) Then
    System.DebugLog(ssh.LastErrorText)
    Return
End If

//  Wait up to 5 seconds for the next channel message.  The return value is the channel number
//  the message belongs to, -1 if nothing arrived before the timeout, or -2 on another error.
Dim pollTimeoutMs As Int32
pollTimeoutMs = 5000
Dim result As Int32
result = ssh.WaitForChannelMessage(pollTimeoutMs)

If (result = -2) Then
    System.DebugLog(ssh.LastErrorText)
    Return
End If

If (result = -1) Then
    System.DebugLog("No channel message arrived before the timeout.")
End If

If (result >= 0) Then
    System.DebugLog("Processed a message for channel " + Str(result))
End If

ssh.Disconnect