XFero: Smart Offline File Transfer

Inspiration

Everyday file sharing is often a hassle - too slow, unreliable, and totally lost when there’s no internet. (Don't even get us started about the WiFi speed at college!) We’ve struggled with failed transfers in college, during hackathons, and even in personal emergencies. XFero was born from the urge to fix this pain for ourselves, and for anyone who depends on sharing urgent files: field clinics, disaster responders, racetrack teams, or just friends at a hostel. We wanted something radically simple, tough enough for the real world, and smart enough to prioritize what actually matters. XFero’s vision is to make sharing files and media so effortless and reliable that it feels like a necessity - not a luxury! Everyone should expect instant, secure sharing as a given, wherever they are.

What it does

XFero is your supercharged file transfer hero - no internet needed! It finds nearby devices instantly and builds a peer-to-peer mesh with WiFi Direct, so files can leap between phones, laptops, or tablets without any setup. Just tag your important files with a "star" and they shoot to the front of the queue. Secrets? They self-destruct after viewing. XFero auto-compresses everything so transfers zoom along, even if your network is crawling.

How we built it

We dove deep into Android WiFi Direct APIs, Bluetooth, and mesh networking. Combining Java sockets, libp2p, and SQLite for storage took quite some time to learn, but it was totally worth the effort! Building mesh routing was a wild ride: the way P2P connections actually work, permissions, NAT traversal, and device discovery were nothing like our prior web projects. Our hackathon experience helped with UI and rapid prototyping, but making mesh file transfer reliable offline was a whole new journey. We crafted simple interfaces for tagging, secure AES encryption for private data and carefully tuned compression using Brotli and LZ4.

Challenges we ran into

P2P networking was harder than we imagined. Devices would connect, then disappear. WiFi Direct’s quirks forced us to rethink how we paired nodes and relayed files. Handling disconnects, retries and building a “just works” mesh took serious trial and error. Debugging mobile mesh topologies, NAT issues, and getting stable peer discovery kept us up late. Balancing encryption, usability and speed was another balancing act because, no matter what, privacy shouldn’t slow anyone down.

Accomplishments that we're proud of

Getting our first successful, offline mesh transfer felt awesome, especially when an urgent tagged file leapfrogged the others. Seeing secrets self-destruct and adaptive compression work under real field conditions excited us. We’re proud that XFero runs with almost zero setup and prioritizes essential files!

What we learned

We learned how mesh networking transforms everyday connectivity and why real resilience means planning for disconnects, chaos and urgency. We discovered that simple UI and smart logic beat complex “features” every time in stressful scenarios. Most of all, we learned the value of trying something genuinely new: even if it meant making mistakes, getting stuck, and figuring it out together!

What's next for XFero: Smart Offline File Transfer

We want to add offline transfer receipts, and wider platform support (Windows, iOS). We're exploring ultra-secure medical workflows and field data collection. But the real mission? To build the easiest, fastest, and most reliable offline sharing tool for everyone - from first responders to everyday friends.

Built With

• bluetooth-api
• brotli4j
• file
• handling:
• java
• java-sockets
• javascript/typescript-(react-native-ui)-frameworks/platforms:-android-sdk
• languages:-java-(main-logic)
• libp2p-java-encryption:-aes-(java)-compression:-java.util.zip
• lz4-java-database:-sqlite-(via-jdbc)-scheduling:-java-timer
• react-native-networking:-android-wifi-direct-api
• scheduledexecutorservice
• webrtc-java-libraries