Pretend that one can succeed to the power-of-two challenge
… Pretend that one that succeed the power-of-two challenge sees the result sent by his server
Pretend that you receive a 404 error when try the power-of-two challenge with a server that is not responding
Pretend that you receive a 501 when your server does not answer the expected answer
And you do :)
Focus on one number when trying the player's server