Adrian Wragg Adrian Wragg - 18 days ago 6
C# Question

Creating a forwarded port within an SSH tunnel

I'm attempting to use SSH.NET to create a tunnel from

localhost:3306
to port 3306 on a remote machine:

PrivateKeyFile file = new PrivateKeyFile(@" .. path to private key .. ");
using (var client = new SshClient(" .. remote server .. ", "ubuntu", file))
{

client.Connect();
var port = new ForwardedPortLocal(3306, "localhost", 3306);
client.AddForwardedPort(port);
port.Start();

// breakpoint set within the code here

client.Disconnect();
}


When the breakpoint is hit,
client.IsConnected
is returning
true
, but
telnet localhost 3306
is not connecting. If I create the connection using Putty instead, and set up the same tunnel there, it succeeds. What have I missed?

Answer

By changing the parameters of ForwardedPortLocal to:

    var port = new ForwardedPortLocal("localhost", 3306, "localhost", 3306);

(to make it explicit which interface I was binding to), and adding the following code in just before port.Start();:

    port.RequestReceived += delegate(object sender, PortForwardEventArgs e)
    {
        Console.WriteLine(e.OriginatorHost + ":" + e.OriginatorPort);
    };

I noticed the following being output:

    ::1:60309

The e.OriginatorHost part of this was ::1, which is the IPv6 equivalent of localhost; however, the destination server was using IPv4. Changing the parameters to:

    var port = new ForwardedPortLocal("127.0.0.1", 3306, "localhost", 3306);

forced the tunnel to run over IPv4 instead, and my code then worked exactly as I'd expected it to.

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