private void challenge_player(Player player, Message message)
 {
     try {
         if (player.IsPlaying) {
             player.Send("Denied", "You are already playing.");
         }
         Player target = FindPlayerByName(message.GetString(0));
         if (target.IsPlaying) {
             player.Send("Denied", "Target is already playing.");
         }
         player.ChallengePlayer(target);
     }
     catch (Exception e) {
         Log("Challenge player message processing failed.", e);
         player.Send("Denied", "Incorrect message format.");
     }
 }