How to implement -Nf and sleep

[wuq5789]

First of all, thanks to ssh.net for such a handy library.

ssh.net how do I implement the following functions of a common SSH client?
ssh -NfL 5555:127.0.0.1:6666 user@192.168.1.1 sleep 30

The focus is on how the functions of -Nf and sleep are implemented.

[Rob-Hague]

We have for the ssh process:

-f

Requests ssh to go to background just before command execution. [...]

Port forwarding in SSH.NET runs in its own thread(s), in effect it would already work in the background.

-N

Do not execute a remote command. This is useful for just forwarding ports. Refer to the description of SessionType in ssh_config(5) for details.

I could be wrong but I think this would mean the sleep command is ignored.

We are left with local port forwarding, something like (untested, adapted from tests in https://github.com/sshnet/SSH.NET/blob/9e1ee0a380873a485a90e7c5778ed83f8dc44a15/test/Renci.SshNet.IntegrationTests/OldIntegrationTests/ForwardedPortLocalTest.cs):

using (var client = new SshClient("host", "port", "user", "pwd"))
{
    client.Connect();

    using var port = new ForwardedPortLocal("127.0.0.1", 5555, "127.0.0.1", 6666);

    port.Exception += (object sender, ExceptionEventArgs e) =>
    {
        Console.Error.WriteLine(e.Exception.ToString());
    };

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

    client.AddForwardedPort(port);
    port.Start();

    // Sleep here as an example, in practice store the client/port somewhere
    // and close it all down when desired
    Thread.Sleep(30 * 1000);

    client.RemoveForwardedPort(port);
    client.Disconnect();
}

Hope it helps!

[wuq5789]

Thank you for your reply
The sleep command is to turn off port forwarding if there is no network data for a certain period of time (e.g., 60 seconds).
Rather than turning off port forwarding after a certain amount of time, as you would understand

[Rob-Hague]

Ok I see, I don't think there is a pre-built way to achieve that. I imagine you might need to hook into the internal code which reads from the local socket

SSH.NET/src/Renci.SshNet/Channels/ChannelDirectTcpip.cs

Line 105 in 7e71bb4

SocketAbstraction.ReadContinuous(_socket, buffer, 0, buffer.Length, SendData);