Hamachi

From OPU Wiki

Hamachi Setup Guide

Install Hamachi on every computer that you wish to play with.

Go into Network Connections, find "Hamachi", open its properties and click 'File and Printer Sharing' component. That's unless you plan on using Windows Sharing over Hamachi.

Create Hamachi network from one of the computer Make other Computers join this network

Ensure that everyone sees everyone with green status in Hamachi list. If not, see yellow status thread in FAQ section.

Ensure that everyone can ping everyone, use peer's right-click menu for that. If ping times out, you will need to check personal firewall settings and make sure it is not blocking pings and game traffic on Hamachi connection. Guides for configuring some popular firewalls are available in HowTo section.

Launch OP2 and select LAN mode. Make someone host a game.