VB.NET

Start an SSH Tunnel Listener (BeginAccepting)

Demonstrates the Chilkat SshTunnel.BeginAccepting method, which creates and starts the local listener on the given port. The only argument is the listen port. Connect and authenticate first — clients accepted before authentication cannot be forwarded. The IsAccepting property reports whether the listener is running.

Background: This is the step that actually turns the object into a working tunnel: it spawns a background thread that accepts local TCP connections and forwards each through the authenticated SSH transport. Because the forwarding runs on its own thread, control returns to your program immediately and the tunnel operates while the rest of the application does other work — which is why a separate CloseTunnel is needed to shut it down cleanly.

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Dim success As Boolean = False

'  Demonstrates the SshTunnel.BeginAccepting method, which creates and starts the local listener
'  on the given port.  The only argument is the listen port.  Connect and authenticate first;
'  clients accepted before authentication cannot be forwarded.

Dim tunnel As New Chilkat.SshTunnel

tunnel.DestHostname = "db.internal.example.com"
tunnel.DestPort = 5432

Dim sshPort As Integer = 22
success = tunnel.Connect("ssh.example.com",sshPort)
If (success = False) Then
    Debug.WriteLine(tunnel.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 = tunnel.AuthenticatePw("mySshLogin",password)
If (success = False) Then
    Debug.WriteLine(tunnel.LastErrorText)
    Exit Sub
End If


'  Start the local listener.  Local TCP connections to this port are forwarded to DestHostname:DestPort
'  through the SSH server.
Dim listenPort As Integer = 1080
success = tunnel.BeginAccepting(listenPort)
If (success = False) Then
    Debug.WriteLine(tunnel.LastErrorText)
    Exit Sub
End If


'  IsAccepting reports whether the listener thread is running.
If (tunnel.IsAccepting) Then
    Debug.WriteLine("The tunnel is accepting connections on port " & listenPort)
End If


'  ... the tunnel forwards traffic on a background thread while your application runs ...

Dim waitForThreadExit As Boolean = True
success = tunnel.CloseTunnel(waitForThreadExit)
If (success = False) Then
    Debug.WriteLine(tunnel.LastErrorText)
    Exit Sub
End If