Jon Wertheim tweeted during the 3rd set
"Petzschner about to go out to Mahut. But if you get a chance it's worth a visit to court 13 on usopen.org just to see pp''s socks"
it was on serve at the time, made me think Mahut broke or something and was serving for the match. Petzschner came through about 2 hours later. Hopefully everyone managed to get online and see his socks. If not there's always his next match