Here's something that bothered me for a while: lsof may incorrectly classify your IPv4 connections as IPv6. $ sudo lsof -i 4:443 $ sudo lsof -i 6:443 COM

Here's something that bothered me for a while: lsof may incorrectly classify your IPv4 connections as IPv6. $ sudo lsof -i 4:443 $ sudo lsof -i 6:443 COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME httpd 12345 apache 6u IPv6 987654321 TCP *:https (LISTEN) If you see this, the fix is to disable IPv6 by setting "options ipv6 disable=1" via modprobe.