Remote access tools are the bread and butter of today’s support technician. For many remote access needs, traditional tools (bundled with the OS, provided by the OS vendor, etc.) are used: RDP, SSH clients/servers, Telnet, etc. Let's see how they compare with each other.
Oftentimes, you (or the remote machine) sit behind a firewall, and your remote access tool wants to work on a fancy port. Accordingly, you might have to open that port on both ends. It presents no difficulty if you have immediate access to network configuration on both ends, which often is *not* the case.