Visual Basic 6.0

SSH Tunnel Timeouts and IP Preference

Demonstrates the ConnectTimeoutMs, IdleTimeoutMs, and PreferIpv6 properties, which govern how long the tunnel waits to connect and to transfer data, and which IP version it prefers.

Background: ConnectTimeoutMs bounds how long a connection attempt blocks — important so an unreachable server fails promptly instead of hanging — while IdleTimeoutMs guards against a stalled transfer holding a connection open indefinitely. PreferIpv6 only matters when a hostname resolves to both address families, choosing which to try first; the default prefers IPv4.

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Visual Basic 6.0

Dim success As Long
success = 0

'  Demonstrates the SshTunnel connection-behavior properties ConnectTimeoutMs, IdleTimeoutMs, and
'  PreferIpv6.

Dim tunnel As New ChilkatSshTunnel

'  Maximum time to establish the SSH connection (default 30000 ms).
tunnel.ConnectTimeoutMs = 10000

'  Stall timeout for tunnel data-transfer operations (default 30000 ms).
tunnel.IdleTimeoutMs = 15000

'  When a hostname resolves to both IPv4 and IPv6, prefer IPv6.  The default (0) prefers IPv4.
tunnel.PreferIpv6 = 1

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

Dim sshPort As Long
sshPort = 22
success = tunnel.Connect("ssh.example.com",sshPort)
If (success = 0) Then
    Debug.Print 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
password = "mySshPassword"

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

Dim listenPort As Long
listenPort = 1080
success = tunnel.BeginAccepting(listenPort)
If (success = 0) Then
    Debug.Print tunnel.LastErrorText
    Exit Sub
End If

Debug.Print "Tunnel established."

Dim waitForThreadExit As Long
waitForThreadExit = 1
success = tunnel.CloseTunnel(waitForThreadExit)
If (success = 0) Then
    Debug.Print tunnel.LastErrorText
    Exit Sub
End If