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Clipboard Forward Center

A lightweight MQTT-based clipboard message forwarding service written in Go. It synchronizes clipboard content between devices with dedup filtering and provides an HTTP API for message storage.

Features

• Forward clipboard messages between MQTT topics based on configurable rules
• Self-forward filtering: automatically skips forwarding a message back to its source device
• SHA256 hash-based dedup filtering with configurable time window
• HTTP API for message storage with Bearer token authentication
• In-memory message store with TTL and configurable capacity
• Automatic MQTT reconnection
• Multi-platform builds via GitHub Actions

Quick Start

# Build
./build.sh v1.0.0

# Edit config
cp config.yaml myconfig.yaml
# Edit myconfig.yaml with your MQTT broker and client settings

# Run
CONFIG_PATH=myconfig.yaml ./clipboard-forward-center start

# With debug logging
DEBUG=1 CONFIG_PATH=myconfig.yaml ./clipboard-forward-center start

Configuration

See config.yaml for a full example.

DSN

MQTT connection string format:

mqtt://user:password@host:port?clientId=id&connectTimeout=3&keepAliveInterval=20&automaticReconnect=true&reconnectMaxInterval=60

Forward Rules

Each rule defines source topics (from) and destination topics (to):

forward:
  - from: ["clipboard-in-text/mobile-k50"]
    to: ["clipboard-out-text/work-min-debian"]
    type: text
    format: json
    contentField: content

• type: Content type identifier (used for dedup hash computation)
• format: Message payload format (json or yaml)
• contentField: Field name in the payload to extract for dedup filtering

Dedup Filter

The filter prevents forwarding duplicate content within a time window:

• Hash = SHA256(type + ":" + contentField_value)
• If the target client has recently sent or received a message with the same hash, the forward is skipped

filter:
  time: 5s  # supports ms/s/m/h, including decimals

Storage

HTTP message storage settings:

storage:
  maxRecords: 100  # max stored messages
  expire: 10m      # message TTL

Clients

Each client has a name and token for HTTP API authentication:

clients:
  - name: mobile-k50
    token: ABCD123456

HTTP API

Write Message

PUT|POST /client/{client}/{msgId}
Authorization: Bearer <token>
Content-Type: application/octet-stream

<message body>

The client in the URL must match the token's associated client name.

Read Message

GET /client/{client}/{msgId}
Authorization: Bearer <token>

Any valid token can read any client's messages (public read access).

CLI Commands

Command	Description
start	Start the service (default)
help	Show help message
download-config	Download config from REMOTE_CONFIG_URL
version	Show version

Environment Variables

Variable	Description	Default
CONFIG_PATH	Config file path	config.yaml
DEBUG	Enable debug logging	(unset)
REMOTE_CONFIG_URL	URL for download-config command	(unset)

Building

./build.sh [version]   # Local build
./test.sh              # Run tests

Pushing a tag (v*) triggers GitHub Actions to build binaries for Linux (amd64/arm64), macOS (amd64/arm64), and Windows (amd64), and creates a GitHub Release.

License

Apache 2.0