You don’t even know that but agreed that if you did then it is useful. If 1 is good enough then you could just stick to the extension the way I started this project. For me it was not. If you go to all that effort you at least want to know, maybe, how useful.
OK, here is a quick and dirty way to know. You will get the output below.
netstat -t4u4wanp | grep -i 'proxy'
We know that it opens 2 connections per client so the ones to 193.187.88.42:443 and/or 141.212.118.18:443 tell you how many there are. We notice that the ones to 0.0.0.0 use our ephemeral ports.
tcp 0 0 10.10.10.10:42926 193.187.88.42:443 ESTABLISHED 1264/proxy
tcp 0 0 10.10.10.10:52406 141.212.118.18:443 ESTABLISHED 1264/proxy
tcp 0 0 10.10.10.10:60734 141.212.118.18:443 ESTABLISHED 1264/proxy
tcp 199394 600 10.10.10.10:42152 193.187.88.42:443 ESTABLISHED 1264/proxy
tcp 0 0 10.10.10.10:49180 193.187.88.42:443 ESTABLISHED 1264/proxy
tcp 0 0 10.10.10.10:40532 141.212.118.18:443 ESTABLISHED 1264/proxy
tcp 0 0 10.10.10.10:58098 141.212.118.18:443 ESTABLISHED 1264/proxy
tcp 0 0 10.10.10.10:51502 193.187.88.42:443 SYN_SENT 1264/proxy
tcp 0 0 10.10.10.10:57356 193.187.88.42:443 ESTABLISHED 1264/proxy
udp 0 0 0.0.0.0:65510 0.0.0.0:* 1264/proxy
udp 0 0 0.0.0.0:65512 0.0.0.0:* 1264/proxy
udp 0 0 0.0.0.0:65513 0.0.0.0:* 1264/proxy
udp 0 0 0.0.0.0:65517 0.0.0.0:* 1264/proxy
udp 0 1280 0.0.0.0:65524 0.0.0.0:* 1264/proxy
udp 0 0 0.0.0.0:65529 0.0.0.0:* 1264/proxy
udp 0 0 0.0.0.0:65530 0.0.0.0:* 1264/proxy
udp 0 0 0.0.0.0:65532 0.0.0.0:* 1264/proxy