This is a free to use Drawpile server.
To host a session here, select the Remote option
in the Host dialog and enter ahaven.net in the text box.
This public server is provided primarily for the benefit of those who are unable to host sessions on their own computers. It has limited capacity, so please be considerate of others and try not to monopolize the available space. To connect to a session via the web, click here to load the web client from the official Drawpile website. If you don't want to draw with anyone else online, click here to load the web client in stand alone mode from the official Drawpile website.
Sessions hosted (or just listed) here should abide by the common community guidelines.
Also, this server has additional rules that can be found here.