WebRTC DataChannel 文件传输：分块、可靠性与重试治理实践

背景与价值DataChannel 支持可靠/不可靠与顺序/无序模式；对文件传输可结合分块与确认协议提升稳定性。基本连接async function setupPeer() {

const pc = new RTCPeerConnection();

const dc = pc.createDataChannel('file', { ordered: true });

dc.onopen = () => console.log('dc-open');

dc.onmessage = (e) => handleMessage(e.data);

const offer = await pc.createOffer(); await pc.setLocalDescription(offer);

// 通过信令交换 SDP 与 ICE 后建立连接

return { pc, dc };

}

分块发送与确认function sendFile(dc: RTCDataChannel, buf: ArrayBuffer, chunkSize = 64 * 1024) {

const u8 = new Uint8Array(buf); let offset = 0; let seq = 0;

const sendChunk = () => {

const end = Math.min(offset + chunkSize, u8.length);

dc.send(JSON.stringify({ type: 'chunk', seq, data: Array.from(u8.slice(offset, end)) }));

offset = end; seq++;

if (offset < u8.length) setTimeout(sendChunk, 0); else dc.send(JSON.stringify({ type: 'end', total: seq }));

};

sendChunk();

}

接收与重组const recv: Record<number, Uint8Array> = {}; let expected = 0;

function handleMessage(raw: string) {

const msg = JSON.parse(raw);

if (msg.type === 'chunk') {

recv[msg.seq] = new Uint8Array(msg.data);

expected = Math.max(expected, msg.seq + 1);

// 可选择发送 ack

} else if (msg.type === 'end') {

const total = msg.total; const out = new Uint8Array(Object.values(recv).reduce((a, b) => a + b.length, 0));

let off = 0; for (let i = 0; i < total; i++) { const c = recv[i]; out.set(c, off); off += c.length; }

onFileComplete(new Blob([out]));

}

}

指标验证（Chrome 128/Edge 130）成功率：弱网下 ≥ 97%。吞吐：稳定在网络允许范围；分块提高健壮性。延迟：中等文件（10–50MB）传输端到端耗时可控；失败重试率 ≤ 3%。回退策略无法建立 P2P：回退到服务器中转或断点续传（TUS/Range）。测试清单大文件与弱网：分块与重组稳定；顺序与可靠模式可选。