zerotier/zerotierone

ZeroTier is a tool that lets your devices, servers, and apps talk to each other over the internet as if they were all plugged into the same private network in the same room. Whether you have a laptop, a phone, a virtual machine, or a cloud server, ZeroTier makes them all appear to be on one shared network, no matter where they actually are in the world. Think of it like a massive invisible Ethernet switch that spans the entire planet. You create a virtual network with a unique ID, and any device that joins that network can reach any other device on it directly and securely. All traffic between devices is encrypted end-to-end using secret keys that only you control, so nobody else can snoop on your data. Most of the time your devices connect directly to each other (peer-to-peer), which keeps things fast. ZeroTier also includes fine-grained access control rules, meaning you can decide exactly which devices can talk to which, making it useful for segmenting different parts of your infrastructure for security. It works on Mac, Linux, Windows, Android, and iOS. You can manage your networks through ZeroTier's hosted service at my.zerotier.com, or run your own controller if you prefer full control. The software is free for internal business and non-commercial use, with a commercial license required for building products on top of it or offering it as a hosted service.