The Internet was created with the idea that any two computers connected to the shared network should be able to communicate with each other. It has also been built on the principles of decentralization, without any central entity having the power to take the network down. Yet, 50 years later, we live in a world where most of the services are centralized and user data are stored on the servers owned by a few large profit-oriented companies. In recent years, the idea of decentralization has attracted many in the engineering and research community. Since the introduction of cryptocurrencies in the last decade, there have been many discussions on whether we can decentralize other services, such as social media, or web. With the trend of decentralization, applications are shifting from the client-server model to peer-to-peer, which brings many challenges and calls for a new networking stack. This thesis proposes and implements a protocol for peer to peer (P2P) communication between any two devices. It is implemented as a Kotlin library which can be used on a desktop, smartphones, tablets, and IoT devices. It can be used to deploy a truly ubiquitous network overlay which is available anytime and everywhere. The protocol allows any two devices to establish a direct connection by taking advantage of NAT traversal techniques to connect peers behind different types of middleboxes. When the Internet connection is not available and peers are located in proximity, the connection can be established using Bluetooth Low Energy. The robustness of the NAT traversal mechanism has been tested by conducting a connectivity check between devices using the networks of major mobile network operators and home broadband providers in the Netherlands. The mechanism has been shown to be capable of establishing a connection in all tested network conditions. To demonstrate the usage of the library, a decentralized social network with public feeds and private end-to-end encrypted messaging has been implemented. To get feedback on the APIs and general usability of the library, 4 teams of MSc students have been asked to develop non-trivial distributed applications on top of it. Compared to the state of the art solutions, the proposed library combines both nearby and Internet connectivity, does not require any central server, works on a variety of devices under challenging network conditions, and is completely open source.