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Reliable transfer between your devices — even on difficult networks.
LAN when possible. Relay when needed. Resume when interrupted.

ShrimpSend / 虾传 runs two official hosted editions from the same open-source codebase. Pick the site that matches where you are:

You can also self-host the full stack on your own infrastructure under AGPL.

This repository (shrimpsend) is the open-source codebase for ShrimpSend / 虾传 — a self-hostable relay for your personal devices. Send text, clipboard snippets, images, videos, and large files between phones, desktops, and browsers. It is built for complex networks: go as fast as your LAN allows on direct paths, keep transfers alive across NAT and restrictive Wi‑Fi, and resume large files after disconnects. It is not a cloud drive and not an “upload, get a link, forward the link” workflow.

• No install for recipients — send directly to browsers and temporary devices when the other side cannot install software.
• Resume after disconnects — large native client ↔ client transfers continue from the interrupted position instead of restarting from 0%.
• Works on restrictive networks — server-assisted relay when hotel Wi‑Fi, campus networks, or carrier NAT block direct reachability.
• Breaks through one-way networks — firewalls and NAT often allow traffic in only one direction (e.g. phone → PC works, PC → phone does not). After sign-in, the server coordinates reachability probes between your devices; if direct HTTP push fails, ShrimpSend automatically reverse-pulls the file from the reachable side, or falls back to WebRTC / S3 relay. See shared/protocol.md.
• LAN-first, still built for speed — prefer direct LAN / WebRTC on the same network; use relay or S3-compatible fallback only when needed.
• Real-time sync — Centrifugo pushes updates to every signed-in client on channel user#<userId>.
• Self-host friendly — run the full stack on your infrastructure under AGPL-3.0-or-later; production secrets stay in private ops templates (docs/SELF_HOST.md).

flowchart LR
  subgraph clients [Clients]
    Flutter[Flutter app]
    Web[Next.js web]
    OHOS[HarmonyOS app_ohos]
  end
  subgraph server [Self_host_stack]
    API[Spring_Boot :9000]
    RT[Centrifugo :8000]
    DB[(MySQL 8 :3306)]
    S3[S3 compatible storage]
  end
  Flutter --> API
  Web --> API
  Flutter --> RT
  Web --> RT
  API --> DB
  API --> S3
  Flutter -. LAN or WebRTC .- Flutter

Transfer paths: on the same LAN, HTTP direct push or reverse pull and optional WebRTC aim for maximum throughput; across restrictive or unstable networks, server-assisted relay and S3-compatible fallback keep delivery reliable. Large native transfers can resume after disconnects. Details: shared/protocol.md.

• Backend: Spring Boot (Java 17), MySQL 8
• Web: Next.js (React)
• Clients: Flutter (iOS, Android, macOS, Windows, Linux), HarmonyOS (app_ohos/)
• Real-time: Centrifugo

Before first ./scripts/start-dev.sh: run cd web && npm ci and ./scripts/install-centrifugo.sh (or run ./scripts/sync-to-build-machine.sh earlier to fetch the Linux binary only). The start script picks scripts/bin/mac/ or scripts/bin/linux/ by OS.

Contributors only: create the MySQL database before first start:

CREATE DATABASE ultrasend CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

Default JDBC: jdbc:mysql://localhost:3306/ultrasend, user root, password changeme. Override via backend/.env (SPRING_DATASOURCE_*).

Logs: scripts/logs/ · PID file: scripts/.dev-pids

Dev scripts live under scripts/ in this repo (not in the private ops repo), so paths to web/, backend/, and config.json resolve correctly. Root ./start-dev.sh / ./stop-dev.sh are shortcuts to scripts/.

Same config step as above (deploy-local.sh or setup-local-config.sh). Maintainers get ultrasend_overseas from deploy-local.sh.

./scripts/start-dev.sh --overseas
# Stop: ./scripts/stop-dev.sh

Uses Spring profile dev-overseas and database ultrasend_overseas. For Stripe membership testing, run in a separate terminal:

stripe listen --forward-to localhost:9000/api/membership/stripe/webhook

Backend-only debugging (no Centrifugo/Web): backend/scripts/run-dev-overseas.sh

Requires an ops config directory synced into this repo. Full steps: docs/SELF_HOST.md.

git clone git@github.com:shrimpsend/shrimpsend.git shrimpsend
cd shrimpsend
git clone git@github.com:shrimpsend/public-ops.git ../ops   # samples; replace placeholders for production
# Maintainers: git clone git@github.com:shrimpsend/ops.git ../ops
# Optional: export ULTRASEND_OPS_DIR=/path/to/your-ops
./scripts/deploy.sh          # interactive: git pull, cn vs overseas, build, restart
./scripts/deploy.sh stop     # stop Centrifugo + backend + Web
./scripts/deploy.sh status
./scripts/deploy.sh logs

Non-interactive overseas deploy:

SPRING_PROFILE=prod-overseas CLUSTER_LABEL='Overseas (ShrimpSend)' ./scripts/deploy.sh

MySQL + Centrifugo + backend in containers; Web still runs on the host.

./scripts/setup-local-config.sh   # or deploy-local for ops/local/docker.env → .env
docker compose up -d
./scripts/start-dev.sh            # Web only path if you skip full stack script

See docs/README.zh-CN.md (Chinese, includes troubleshooting) · docs/SELF_HOST.md

cd app
flutter pub get
flutter run
# Optional overrides:
# flutter run --dart-define=API_URL=http://localhost:9000 \
#   --dart-define=CENTRIFUGO_WS=ws://localhost:8000/connection/websocket

OpenPanel secrets and analytics: app/README.md.

Full guide: docs/SELF_HOST.md · Chinese setup: docs/README.zh-CN.md

Trademarks ShrimpSend / 虾传 are not licensed under AGPL. Community forks must:

1. Not ship under the ShrimpSend / 虾传 name, logo, or confusingly similar branding (including app stores).
2. Use distinct application names and package/bundle IDs (Flutter applicationId, iOS bundle ID, etc.).
3. Default API/WebSocket endpoints to your servers — not api.shrimpsend.com or api.xiachuan.net.
4. Clearly state the deployment is independent (e.g. “AcmeSend — self-hosted, not affiliated with ShrimpSend”).

Official hosted services (reference only): shrimpsend.com (international), xiachuan.net (China). Full policy: TRADEMARK.md.

shrimpsend/
├── backend/          # Spring Boot API
├── web/              # Next.js web app
├── app/              # Flutter clients
├── app_ohos/         # HarmonyOS
├── ops/              # Production templates (secrets gitignored)
├── shared/           # Protocol notes
├── config.json       # Centrifugo (generated locally)
└── docker-compose.yml

• User registration/login, JWT auth
• Device registry with unique deviceId and display names
• Real-time messages on user#<userId>
• Text + file messages (S3 presigned upload/download)
• Per-send choice: all devices (S3) or a specific peer (LAN direct when possible)
• Browser receive without asking others to install the app
• Resume large transfers after network drops (native client ↔ client)
• Server-assisted paths across NAT, campus Wi‑Fi, and carrier networks (signed-in)
• Settings: S3 credentials, device list, renames

Issues and pull requests: github.com/shrimpsend/shrimpsend. Read CONTRIBUTING.md (DCO sign-off required: git commit -s).

SPDX: AGPL-3.0-or-later

ShrimpSend / 虾传 is released under the GNU Affero General Public License v3.0 or later. You may use, modify, and self-host freely; if you modify the software and offer network access to users, AGPL requires making corresponding source available to those users.