ngrep works on macos/Darwin without problems. The official page even
states that:
```
Confirmed Working Platforms
Linux 2.0+ (RH6+, SuSE, TurboLinux, Debian, Gentoo, Ubuntu, Mandrake, Slackware)/x86, RedHat/alpha Cobalt, (Qube2) Linux/MIPS
Solaris 2.5.1, 2.6/SPARC, Solaris 7, Solaris 8/SPARC, Solaris 9/SPARC
FreeBSD 2.2.5, 3.1, 3.2, 3.4-RC, 3.4-RELEASE, 4.0, 5.0
OpenBSD 2.4 (after upgrading pcap from 0.2), 2.9, 3.0, 3.1+
NetBSD 1.5/SPARC
Digital Unix V4.0D (OSF/1), Tru64 5.0, Tru64 5.1A
HPUX 11
IRIX
AIX 4.3.3.0/PowerPC
BeOS R5
Mac OS X 10+
GNU HURD
Windows 95, 98, NT, 2000, XP, 2003/x86, 7, 8, 8.1, 10
```