TransportChat is a lightweight, local-network-only chat and file transfer app for Android. It discovers peers on the same LAN using Android NSD (DNS-SD), establishes an encrypted session for each connection, and never relies on any cloud server. Zero server: peer-to-peer over your LAN (Wi-Fi / hotspot). Encryption: ephemeral key exchange and per-session encryption. Discovery: automatic via DNS-SD (_lanonlychat._tcp.), plus manual connect. Clean notifications: sanitized — show who sent a message, never the preview. Blocking: block a peer and their messages won’t be delivered (no silent “delivered” ack). Renames: rename chats/peers for this session only (not persisted). Clear chats: per-chat “Clear chat” action. File transfer: fast LAN transfers with inline progress. Features LAN-only peer discovery via Android NSD/DNS-SD service type _lanonlychat._tcp. Manual connect to host:port if discovery is unavailable. Encrypted sessions with ephemeral keys per connection. Sanitized notifications: only the sender name appears. Blocklist (local): blocked peers are refused before handshake — their sender won’t see “Delivered”. Session-only rename: rename a peer/chat for the current run (labels reset after app restart). Clear chat: remove local chat history per peer on demand. File transfers: offer/accept with progress indicators; received files open via standard Android intents. Read receipts: show sending, delivered, and read indicators for messages you send. Screens & Controls Peers Shows discovered peers on your LAN and an unread badge. ⋮ (more) per peer → Send Chat (open conversation), Rename Chat (session-only label). Refresh: re-starts a discovery pass. Manual Connect: enter Host/IP and Port to connect to a peer directly. Chat Title reflects the (session-only) label and endpoint. Send messages and Attach files. ⋮ menu: Clear chat, Block/Unblock this peer. Read status shows “Sending…”, “✓ Delivered”, or “✓✓ hh:mm”. Blocked behavior: When you block a peer, your server drops their connections immediately (no handshake, no ack). They won’t see “Delivered”. Permissions These are typically required: <!-- AndroidManifest.xml --> <uses-permission android:name="android.permission.INTERNET" /> <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" /> <uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE" /> <!-- Android 13+ (API 33): runtime permission --> <uses-permission android:name="android.permission.POST_NOTIFICATIONS" /> INTERNET: TCP connections on your LAN. ACCESS_WIFI_STATE: obtain IP and control multicast lock for discovery. CHANGE_WIFI_MULTICAST_STATE: receive multicast DNS packets for discovery. POST_NOTIFICATIONS: user-visible notifications on Android 13+. On Android 13+, the app will request notification permission at first launch. How It Works Discovery: peers advertise via Android NSD as _lanonlychat._tcp.; the app resolves services and filters out itself. Handshake & Encryption: when sending text or file offers, the client performs a handshake, exchanges ephemeral keys, and encrypts frames. Delivery & Read: the server replies with encrypted DELIVERED or READ acknowledgements as appropriate. Blocking: server checks the blocklist at accept time and closes blocked sockets before handshake. No ack is sent. Privacy & Security Local-only by design — no central server. Sanitized notifications — show the sender name only (no message preview). Blocklist enforced server-side — blocked peers cannot deliver messages or file offers. Ephemeral labels — renamed titles are not persisted and vanish after app restart. Use on trusted LANs. While sessions are encrypted, network operators can observe connection metadata typical to LAN apps.