May be... I am also trying 443 port as well as 9999 etc.
Now miner's log says:
"
Stratum authentication failed.
... retry after 30 seconds
"
then, just as if nothing had happened,
"
Stratum detected new block
... yay!!!
"
And so on, the whole day, from two independent city places, internet providers, & both GPU & CPU miners...
Yesterday all was fine