B4X

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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Dim success As Boolean = False

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

Dim tunnel As ChilkatSshTunnel
tunnel.Initialize("tunnel")

'  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 (False) prefers IPv4.
tunnel.PreferIpv6 = True

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

Dim sshPort As Int = 22
success = tunnel.Connect("ssh.example.com", sshPort)
If success = False Then
    Log(tunnel.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 = "mySshPassword"

success = tunnel.AuthenticatePw("mySshLogin", password)
If success = False Then
    Log(tunnel.LastErrorText)
    Return
End If


Dim listenPort As Int = 1080
success = tunnel.BeginAccepting(listenPort)
If success = False Then
    Log(tunnel.LastErrorText)
    Return
End If

Log("Tunnel established.")

Dim waitForThreadExit As Boolean = True
success = tunnel.CloseTunnel(waitForThreadExit)
If success = False Then
    Log(tunnel.LastErrorText)
    Return
End If