Category: web and tech

Configuring SoftEther VPN on Ubuntu with a firewall

DigitalOcean has a good article on setting SoftEther VPN on one of their droplets.

The instructions worked for me without just fine, with a couple exceptions:

1. When you attempt to use the command line vpncmd tool to set up the server, you may have to specify localhost:5555 rather than using the defaults.

2. You may have to create a group for the test user before creating them and assigning them to a test group. This can be done with the command `GroupCreate test`.

3. If you are using a firewall, you will need to open up the ports used by SoftEther. To figure out what ports it’s using, do `sudo netstat -atulpn  | grep vpnserver`. By default, SoftEther will listen on TCP ports 443, 992, and 5555. If you’re using L2TP/IPsec, make sure UDP ports 500 and 4500 are open as well. If you’re using ufw for your firewall, you can see which ports are open/blocked with `sudo ufw status verbose`. To get an idea of which ports each VPN protocol you’re using requires, check out the SoftEther specifications.

Throttle outbound Spotify traffic

When working on a shared network with limited bandwidth, it’s sometimes nice to be able to keep listening to Spotify without ruining your co-workers’ Internet connections.

Spotify is P2P (the desktop app is, anyway), so you both receive data from other Spotify users and transmit it to them. Blocking the outgoing traffic entirely would be un-neighbourly (probably also a violation of TOS), and might even prevent streaming from working altogether.

Fortunately, as I just discovered, ipfw allows you to add a pipe to a range of ports, all of which you can then throttle to a certain data transfer rate. It’s a shotgun approach, and will slow down any other services that are trying to send data over those ports as well, but since Spotify seems to stick to the range 10000 to 80000, and I rarely if ever run anything of consequence on those ports, this approach works for me.

sudo ipfw add pipe 1 ip from any to any out dst-port 10000-80000
sudo ipfw pipe 1 config bw 8KBytes/s

Cisco IPsec VPN on OSX Snow Leopard

For anyone else having issues setting up a VPN connection on Snow Leopard: if you are getting an “incorrect shared secret” error, quit wasting your time, and download Shimo, a VPN client for OSX. Haven’t paid for it yet, but will likely end up doing so, since it’s the only one of a half-dozen or so that I tried that not only worked, but wasn’t horribly designed.

I suspect my issue may have been related to a the VPN shared secret being too long, though that is mostly speculation. There was mention in a forum somewhere that OSX Lion silently truncates shared secret keys longer than 63 characters. Yay.

Errors in scripts loaded with jQuery $.getScript

Spent some time the other day trying to figure out why I wasn’t seeing JavaScript errors in certain files where I expected to, which was problematic both for development and also for the monitoring of client-side errors we’re doing in the application (assigning a handler to window.onerror that makes an ajax call with error information to an endpoint for this purpose).

Basically, if there are errors in any of the scripts you are loading with $.getScript, or the full $.ajax call for which $.getScript is shorthand, these will be caught by jQuery and will fail to show up in the console or be passed to any window.onerror handler you’ve defined. jQuery provides a global ajaxHandler you can attach to, for example, document, which you can then use to do whatever client-side error handling/logging you want to do.

The downside of this approach is (as far as I can tell) that you don’t get quite as much error information (specifically, the line number of the error) from jQuery as you do from other ways of loading scripts with js, because the error gets caught during a call to eval (or more specifically, jQuery’s globalEval method).

Objects in closure compiler record types

I’ve been diving much deeper into closure compiler’s type checking abilities lately, and while it is a great tool, the documentation could stand to be improved somewhat.

Sometimes when creating a record type, you will want to specify not just that some property is an array, or an object, but what sort of things are in the array, or what sort of properties are on the object.

A simple record type for an object with a string and number property:


/**
 * @typedef {{name: string, index: number}}
 */

A record type with an array of strings:


/**
 * @typedef {{networks: Array.<string>}}
 */

A record type, one of whose properties is an object:


/**
 * @typedef {{authorized:boolean, network_name: string,
 * details: Object.<{id: number, promotion_id: number}>, type: string}}
 */

 

This last one is the syntax I was having trouble coming up with, and it is not immediately obvious from the official documentation here. Hope this might help someone else who’s looking for the same thing.

Also, an example of objects inside an array (using this for a Vimeo video object):


/**
 * @typedef {{urls: {url: Array.<Object.<{type: string, _content: string}>>},
 * thumbnails: {thumbnail: Array.<Object.<{_content: string, width: string, height: string}>>} }}
 * }}
 */

 

You can also refer to other record types inside a record type:


/**
 * @typedef {{name: string, auth_provider: string, id: number}}
 */
MyRecordTypes.authorization;

/**
 * @typedef {{authorizations: Array.<MyRecordTypes.authorization> }}
 */
MyRecordTypes.authorizations;