dns2tcp software package provides TCP over DNS tunnel client and server, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install dns2tcp
dns2tcp is installed in your system.
Make ensure the dns2tcp package were installed using the commands given below,
$ sudo dpkg-query -l | grep dns2tcp *
You will get with dns2tcp package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Network |
| Package | dns2tcp |
| Version | 0.5.2-1.1+b1 [s390x], 0.5.2-1. |
| Description | TCP over DNS tunnel client and server |
| Sub Section | Net |