It is important that you set up the contest environment and test it well ahead of the event. A mock contest is often hosted to test the environment before the main contest.
When setting up an on-site contest environment, make sure you:
Check that the contestants’ computers have one of the supported web browsers installed.
The local date, time, and timezone of the computer are set correctly.
toph.co, static.toph.co and uploads.toph.co are all reachable.
WebSockets are not blocked.
The Internet connection can provide sufficient bandwidth for all of the participants.
You can use Toph’s Compatibility Tester to check all of these.
When setting up a local environment for contestants, ensure that you provide compiler and interpreter versions as close as possible to those used by Toph.
One of the best ways of restricting access to the Internet during contest is through the use of firewall rules at the router level.
Rejecting all outgoing packets to destinations other than toph.co, static.toph.co and uploads.toph.co should do the job. The relevant IP addresses can be found by performing an A record DNS lookup for those hostnames.
$ getent hosts toph.co $ getent hosts static.toph.co $ getent hosts uploads.toph.co