​

Peer-to-Peer File Transfer

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WebRTC DataChannel Implementation

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Connection Establishment

// From network.js lines 1126-1129
const channel = this._conn.createDataChannel('data-channel', {
    ordered: true,
    reliable: true // Obsolete but maintained for compatibility
});

​

Binary Data Transfer

// From network.js lines 1177-1178
channel.binaryType = 'arraybuffer';
channel.onmessage = e => this._onMessage(e.data);

​

Transfer Capabilities

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Supported File Types

• All File Types: No restrictions on file formats
• Large Files: Limited only by browser memory and network constraints
• Multiple Files: Simultaneous transfer of multiple files and folders
• Directory Support: Complete directory structure preservation

​

Transfer Performance

• Direct Connection: No server bandwidth consumption
• Network Speed: Limited only by local network capabilities
• Concurrent Transfers: Multiple simultaneous transfers supported
• Resume Capability: Automatic retry for interrupted transfers

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Security Features

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End-to-End Encryption

// WebRTC provides automatic DTLS/SRTP encryption
this._conn = new RTCPeerConnection(this.rtcConfig);
// All data is encrypted by the browser automatically

​

Connection Authentication

• Certificate Exchange: WebRTC handles certificate exchange automatically
• Fingerprint Verification: Connection hashes for security validation
• Perfect Forward Secrecy: Each session uses unique encryption keys

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Transfer Process

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1. Discovery Phase

• Local Network: Automatic IP-based discovery
• Device Pairing: Persistent connections using room secrets
• Public Rooms: Temporary 5-character room codes

​

2. Connection Phase

// From network.js lines 1104-1113
_connect() {
    if (!this._conn || this._conn.signalingState === "closed") 
        this._openConnection();

    if (this._isCaller) {
        this._openChannel();
    } else {
        this._conn.ondatachannel = e => this._onChannelOpened(e);
    }
}

​

3. Transfer Phase

• Request/Accept: Transfer request and user confirmation
• Metadata Exchange: File information transmission
• Chunked Transfer: 64KB chunks for memory efficiency
• Progress Tracking: Real-time progress updates

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File Chunking System

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Chunk Size Optimization

// From network.js lines 1671-1672
this._chunkSize = 64000; // 64 KB chunks
this._maxPartitionSize = 1e6; // 1 MB partitions

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Memory Management

• Streaming: Files processed in chunks to prevent memory overload
• Buffer Control: Efficient buffer management for large files
• iOS Optimization: Special handling for iOS memory limits

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Network Optimization

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Connection Reuse

// From network.js lines 1287-1295
refresh() {
    if (this._isConnected() || this._isConnecting()) return;
    if (!this._isCaller) return;
    this._connect();
}

​

Adaptive Performance

• ICE Candidate Selection: Optimal network path selection
• Connection Monitoring: Real-time connection quality assessment
• Automatic Fallback: WebSocket fallback when WebRTC fails

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Error Handling

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Connection Recovery

// From network.js lines 1241-1243
_onChannelClosed() {
    console.log('RTC: channel closed', this._peerId);
    Events.fire('peer-disconnected', this._peerId);
    if (!this._isCaller) return;
    this._connect(); // reopen the channel
}

​

Transfer Reliability

• Automatic Retry: Failed chunks are automatically resent
• Progress Preservation: Transfer progress is maintained during retries
• Graceful Degradation: Fallback to WebSocket when necessary

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Performance Metrics

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Transfer Speed

• Local Network: Typically 50-200+ MB/s on Gigabit networks
• WiFi Networks: 10-50 MB/s depending on signal quality
• Mobile Networks: 1-10 MB/s depending on connection quality

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Latency

• Connection Setup: 1-3 seconds for WebRTC establishment
• Transfer Latency: Sub-millisecond for local networks
• Response Time: Real-time progress updates

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Browser Compatibility

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WebRTC Support Detection

// From network.js lines 1425-1434
if (window.isRtcSupported && rtcSupported) {
    this.peers[peerId] = new RTCPeer(this._server, isCaller, peerId, roomType, roomId, this._wsConfig.rtcConfig);
} else if (this._wsConfig.wsFallback) {
    this.peers[peerId] = new WSPeer(this._server, isCaller, peerId, roomType, roomId);
}

​

Supported Browsers

• Chrome 23+: Full WebRTC support
• Firefox 22+: Full WebRTC support
• Safari 11+: WebRTC support with some limitations
• Edge 79+: Full WebRTC support (Chromium-based)

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Advanced Features

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Connection Hashing

// From network.js lines 1193-1217
getConnectionHash() {
    const localDescriptionLines = this._conn.localDescription.sdp.split("\r\n");
    const remoteDescriptionLines = this._conn.remoteDescription.sdp.split("\r\n");
    // Extract and combine fingerprints for unique connection identification
    const combinedFingerprints = this._isCaller
        ? localConnectionFingerprint + remoteConnectionFingerprint
        : remoteConnectionFingerprint + localConnectionFingerprint;
    return cyrb53(combinedFingerprints).toString();
}

​

Multi-Room Support

• Simultaneous Rooms: Single peer in multiple room types
• Flexible Discovery: IP-based, secret-based, and public rooms
• Dynamic Switching: Seamless switching between room types

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Use Cases

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Personal File Sharing

• Document Transfer: Quick sharing between work and personal devices
• Media Sharing: Photo and video sharing between devices
• Backup: Simple backup between computers and mobile devices

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Professional Use

• Collaboration: File sharing during meetings
• Development: Quick code and asset sharing
• Presentations: Transfer presentation files between devices

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Emergency Scenarios

• No Internet: Works completely offline on local networks
• Remote Areas: No dependency on cloud services
• Privacy: No third-party access to transferred files