DHIVA LABS · LEARN

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Networking and SSH ​

Learn how devices find and talk to each other on a network, then use SSH to sign in to a computer you own, copy files to it, reach its services through a tunnel, and lock it down.

What you will be able to do ​

By the end of this track you can:

  • read an IP address and tell whether it is private, public or "this device";
  • find your computer's address and see which programs are listening on which ports;
  • tell from an error message whether a name, a port or a firewall is the problem;
  • turn on an SSH server on Ubuntu or Windows, connect to it, and check that you reached the right machine;
  • make an SSH key, install it on a server and take it away again;
  • reach a service on another computer through an SSH tunnel without opening it to the network;
  • set an SSH server to accept keys only, and undo the change if something goes wrong.

Who it is for ​

Students, testers, new developers and curious home users. You need no networking background. You should be comfortable typing a command in a terminal and pressing Enter.

For the lab you need a Linux computer of your own and either an Android phone or a second Linux computer.

The lessons ​

Read them in order. Each one builds on the one before.

Lesson 1Networks, addresses and portsIP addresses, your home router, ports, DNS, firewalls, and how to see it all.Lesson 2SSH: sign in to another computerWhat happens when you connect, host keys, copying files, and turning on an SSH server.Lesson 3SSH keysKey pairs, passphrases, authorized_keys, agents, and removing a key you no longer trust.Lesson 4SSH tunnelsLocal, remote and dynamic forwards, who can use them, and how they differ from public tunnels.Lesson 5Secure your SSH serverKeys only, firewalls, updates, watching who signs in, and public Wi-Fi habits.LabYour own SSH serverTurn on SSH, connect from SecureShell Go, switch to a key, copy files and tunnel to a mock API.

How long it takes ​

Each lesson takes 15 to 25 minutes, including its quiz. The lab takes 45 to 60 minutes. Plan on about three hours in all, in as many sittings as you like.

Apps that use this knowledge ​

AppWhat it does with the networkGuide
SecureShell GoSSH terminal, SFTP files, host-key checks, keys and tunnels on Android and LinuxSecureShell Go
CrossShellTurns on OpenSSH on Linux and Windows machines, pairs them and swaps keysCrossShell
NearShareFinds nearby devices with mDNS and sends files over your local networkNearShare
SysVitalsThe Ports tab shows every listening port and the program behind itNetwork connections and ports
Mock StudioServes mock APIs on your network, to emulators, and through public tunnelsShare on LAN or the internet
WinBridgeDrives a Windows virtual machine over SSH with a key of its ownBuild Flutter apps on a Windows VM

A word before you start ​

Everything in this track is meant for computers and networks you own, or that you have clear permission to use. Signing in to, scanning or tunnelling into someone else's machine without permission is wrong and, in many countries, a crime.

Next steps ​