Hello Kashish,
yes the same problem to me with firefox and opera browser. Catalina Version
I tried lsof... but
The default interactive shell is now zsh.
To update your account to use zsh, please run `chsh -s /bin/zsh`.
For more details, please visit https://support.apple.com/kb/HT208050.
Peters-MacBook-Air-2:~ peter$ lsof -i:10391
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Enpass 15554 peter 20u IPv4 0x3519d6b4a400b3a3 0t0 TCP localhost:10391 (LISTEN)
Enpass 15554 peter 31u IPv4 0x3519d6b4a58e3e23 0t0 TCP localhost:10391->localhost:53773 (CLOSE_WAIT)
firefox 37933 peter 26u IPv4 0x3519d6b4a95919e3 0t0 TCP localhost:50602->localhost:10391 (SYN_SENT)
firefox 37933 peter 89u IPv4 0x3519d6b4a59a4ca3 0t0 TCP localhost:50603->localhost:10391 (SYN_SENT)
firefox 37933 peter 127u IPv4 0x3519d6b4a45063a3 0t0 TCP localhost:50615->localhost:10391 (SYN_SENT)
firefox 37933 peter 131u IPv4 0x3519d6b4a5968723 0t0 TCP localhost:50618->localhost:10391 (SYN_SENT)
Peters-MacBook-Air-2:~ peter$
After changing the shell
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
Enpass 15554 peter 20u IPv4 0x3519d6b4a400b3a3 0t0 TCP localhost:10391 (LISTEN)
Enpass 15554 peter 31u IPv4 0x3519d6b4a58e3e23 0t0 TCP localhost:10391->localhost:53773 (CLOSE_WAIT)
firefox 37933 peter 89u IPv4 0x3519d6b4abe01e23 0t0 TCP localhost:50811->localhost:10391 (SYN_SENT)
firefox 37933 peter 90u IPv4 0x3519d6b4a654a463 0t0 TCP localhost:50813->localhost:10391 (SYN_SENT)