If you’re using a recent version of Debian/Ubuntu, you can find sngrep in the official Debian/Ubuntu repositories. 

Otheriwse, you can use Irontec repositories for some of Debian and Ubuntu releases.

Binaries are built only for amd64 and i386 architectures right now with all supported features enabled.

Debian

Add Irontec repositories entry in your /etc/apt/sources.list
Use your distrubution source line (only one of these)

deb http://packages.irontec.com/debian squeeze main
deb http://packages.irontec.com/debian wheezy main
deb http://packages.irontec.com/debian jessie main
deb http://packages.irontec.com/debian stretch main

Ubuntu

Add Irontec repositories entry in your /etc/apt/sources.list
Use your distrubution source line (only one of these)

deb http://packages.irontec.com/ubuntu trusty main
deb http://packages.irontec.com/ubuntu precise main
deb http://packages.irontec.com/ubuntu vivid main
deb http://packages.irontec.com/ubuntu xenial main
deb http://packages.irontec.com/ubuntu zesty main
deb http://packages.irontec.com/ubuntu artful main

Install Repository key

wget http://packages.irontec.com/public.key -q -O - | apt-key add -

Install the package

apt-get update
apt-get install sngrep

CentOS / Fedora / RHEL

You can use Irontec repositories for some of CentOS (5,6,7), Fedora (20,21) and Red Hat versions (5,6,7).
Binaries are built only for amd64 and i386 architectures without SSL support.

Add Irontec repo information to /etc/yum.repos.d/irontec.repo

For Centos:

[irontec]
name=Irontec RPMs repository
baseurl=http://packages.irontec.com/centos/$releasever/$basearch/

For Fedora:

[irontec]
name=Irontec RPMs repository
baseurl=http://packages.irontec.com/fedora/$releasever/$basearch/

For Red Hat Enterprise Linux:

[irontec]
name=Irontec RPMs repository
baseurl=http://packages.irontec.com/rhel/$releasever/$basearch/

Add Irontec repositories public key:

rpm --import http://packages.irontec.com/public.key

And install the package

yum install sngrep

Alpine Linux

sngrep is available in community repositories starting from Alpine v3.3 (Thx Francesco Colista!)

Decomment community repository from /etc/apk/repositories (if commented)

Update your package list

apk update

Install sngrep

apk add sngrep

Gentoo

You can find an unofficial ebuilds for sngrep at Gentoo Bugtracker System (Thanks to spacedream)

Feel free to vote if you would like to see sngrep be part of Gentoo portage tree.

Arch

You can find an unofficial PKGBUILD for Arch at ArchLinux User Repositories (thanks to w1ngnutt)

Feel free to vote if you would like to see sngrep at official Arch repositories.

OSX

OSX users can install sngrep using homebrew

brew install sngrep

OpenWRT/LEDE

You can use official repositories for installing sngrep using:

opkg install sngrep