Add tcp option to set keep alive value on the tcp layer

[mogaleaf]

Hi,

Our devices have bandwidth constraint and we can't use the default 15s tcp keep-alive from the go sdk library.
I have set up an option to be able to change it as it is impossible to do so with the library.

Let me know if it could be integrated to the library.

Signed-off-by: cecile cecile.thiebaut@gmail.com

[MattBrittan]

Thanks for this; I can see why it might be useful. However I'm not completely comfortable with the implementation due to the added complexity (extra config structure TcpOptions etc) and, if we are allowing the user to configure this, then why not other Dialer options (potentially LocalAddr and FallbackDelay could be useful).

I wonder if it would be simpler to add a Dialer net.Dialer in ClientOptions (default to net.Dialer{} and have SetConnectTimeout manipulate that). You could then add a SetDialer that provides a fully custom Dialer. The Dialer could then be passed into openConnection (simplifying that function). This would mean importing net into options.go but as this already imports a couple of net packages I don't see that being an issue.

[mogaleaf]

I have implemented the changes using net.Dialer directly into options.
Set up default timeout to 30 * time.Second for backward compatibility.
ConnectTimeout is used for WebSocket too so I need to keep it at options level and dialer level.
Let me know what you think about this option.

Thanks

[MattBrittan]

Thanks very much,
As you say having the options ConnectTimeout and Dialer is not ideal but I think working around that is likely to introduce further confusion (the alternative being to pass dialer.Timeout to openConnection). The way this is implemented now should provide maximum flexibility with minimal code changes. This passes the tests so I'll accept it.

Matt