react · huntie · Jul 19, 2026
diff --git a/packages/rn-tester/js/examples/WebSocket/BinanceWebSocketDemo.js b/packages/rn-tester/js/examples/WebSocket/BinanceWebSocketDemo.js
@@ -0,0 +1,340 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+import type {RNTesterModuleExample} from '../../types/RNTesterTypes';
+
+import RNTesterText from '../../components/RNTesterText';
+import * as React from 'react';
+import {useCallback, useEffect, useRef, useState} from 'react';
+import {FlatList, Pressable, StyleSheet, View} from 'react-native';
+
+const STREAM_URL = 'wss://stream.binance.com:9443/ws';
+const MAX_LOG_ENTRIES = 30;
+
+type TradeSymbol = 'btcusdt' | 'ethusdt' | 'solusdt';
+type ConnectionState = 'idle' | 'connecting' | 'open' | 'closed';
+type FrameLogEntry = Readonly<{
+  id: string,
+  direction: 'sent' | 'received',
+  time: string,
+  summary: string,
+}>;
+
+const SYMBOLS: ReadonlyArray<TradeSymbol> = ['btcusdt', 'ethusdt', 'solusdt'];
+
+const STATE_COLOR = {
+  idle: '#999999',
+  connecting: '#e6a700',
+  open: '#2e7d32',
+  closed: '#c62828',
+};
+
+function nowTime(): string {
+  const d = new Date();
+  const pad = (n: number): string => String(n).padStart(2, '0');
+  return `${pad(d.getHours())}:${pad(d.getMinutes())}:${pad(d.getSeconds())}`;
+}
+
+component BinanceWebSocketDemo() {
+  const [state, setState] = useState<ConnectionState>('idle');
+  const [symbol, setSymbol] = useState<TradeSymbol>('btcusdt');
+  const [price, setPrice] = useState<?string>(null);
+  const [log, setLog] = useState<Array<FrameLogEntry>>([]);
+  const wsRef = useRef<?WebSocket>(null);
+  const idRef = useRef<number>(0);
+
+  const appendLog = useCallback(
+    (direction: 'sent' | 'received', summary: string) => {
+      idRef.current += 1;
+      const entry: FrameLogEntry = {
+        id: String(idRef.current),
+        direction,
+        time: nowTime(),
+        summary,
+      };
+      setLog(prev => [entry, ...prev].slice(0, MAX_LOG_ENTRIES));
+    },
+    [],
+  );
+
+  const send = useCallback(
+    (method: 'SUBSCRIBE' | 'UNSUBSCRIBE', target: TradeSymbol) => {
+      const ws = wsRef.current;
+      if (ws == null || ws.readyState !== WebSocket.OPEN) {
+        return;
+      }
+      idRef.current += 1;
+      ws.send(
+        JSON.stringify({
+          method,
+          params: [`${target}@trade`],
+          id: idRef.current,
+        }),
+      );
+      appendLog('sent', `${method} ${target}@trade`);
+    },
+    [appendLog],
+  );
+
+  const connect = useCallback(() => {
+    if (wsRef.current != null) {
+      return;
+    }
+    setState('connecting');
+    setLog([]);
+    const ws = new WebSocket(STREAM_URL);
+    wsRef.current = ws;
+
+    ws.onopen = () => {
+      setState('open');
+      send('SUBSCRIBE', symbol);
+    };
+
+    ws.onmessage = event => {
+      try {
+        const data: {e?: string, s?: string, p?: string} = JSON.parse(
+          String(event.data),
+        );
+        const tradePrice = data.p;
+        if (data.e === 'trade' && tradePrice != null) {
+          setPrice(tradePrice);
+          appendLog('received', `trade ${data.s ?? ''} @ ${tradePrice}`);
+        } else {
+          appendLog('received', String(event.data).slice(0, 80));
+        }
+      } catch (error: unknown) {
+        appendLog('received', String(event.data).slice(0, 80));
+      }
+    };
+
+    ws.onerror = () => {
+      appendLog('received', 'error event');
+    };
+
+    ws.onclose = () => {
+      setState('closed');
+      wsRef.current = null;
+    };
+  }, [appendLog, send, symbol]);
+
+  const disconnect = useCallback(() => {
+    wsRef.current?.close();
+  }, []);
+
+  const changeSymbol = useCallback(
+    (next: TradeSymbol) => {
+      if (next === symbol) {
+        return;
+      }
+      send('UNSUBSCRIBE', symbol);
+      send('SUBSCRIBE', next);
+      setSymbol(next);
+      setPrice(null);
+    },
+    [send, symbol],
+  );
+
+  useEffect(() => {
+    return () => {
+      wsRef.current?.close();
+    };
+  }, []);
+
+  const busy = state === 'connecting' || state === 'open';
+
+  return (
+    <View style={styles.container}>
+      <View style={styles.statusRow}>
+        <View
+          style={[styles.statusDot, {backgroundColor: STATE_COLOR[state]}]}
+        />
+        <RNTesterText style={styles.statusText}>
+          {state.toUpperCase()}
+        </RNTesterText>
+      </View>
+
+      <RNTesterText variant="label" style={styles.symbolLabel}>
+        {symbol.toUpperCase()}
+      </RNTesterText>
+      <RNTesterText style={styles.price}>
+        {price != null ? `$${Number(price).toFixed(6)}` : '—'}
+      </RNTesterText>
+
+      <View style={styles.symbolRow}>
+        {SYMBOLS.map(s => (
+          <Pressable
+            key={s}
+            onPress={() => changeSymbol(s)}
+            style={[
+              styles.symbolButton,
+              s === symbol && styles.symbolButtonActive,
+            ]}>
+            <RNTesterText
+              style={[
+                styles.symbolButtonText,
+                s === symbol && styles.symbolButtonTextActive,
+              ]}>
+              {s.replace('usdt', '').toUpperCase()}
+            </RNTesterText>
+          </Pressable>
+        ))}
+      </View>
+
+      <View style={styles.controlsRow}>
+        <Pressable
+          style={[styles.controlButton, busy && styles.controlButtonDisabled]}
+          disabled={busy}
+          onPress={connect}>
+          <RNTesterText style={styles.controlButtonText}>Connect</RNTesterText>
+        </Pressable>
+        <Pressable
+          style={[
+            styles.controlButton,
+            state !== 'open' && styles.controlButtonDisabled,
+          ]}
+          disabled={state !== 'open'}
+          onPress={disconnect}>
+          <RNTesterText style={styles.controlButtonText}>
+            Disconnect
+          </RNTesterText>
+        </Pressable>
+      </View>
+
+      <RNTesterText variant="label" style={styles.logHeader}>
+        Frame log ({log.length})
+      </RNTesterText>
+      <FlatList
+        style={styles.log}
+        data={log}
+        keyExtractor={item => item.id}
+        renderItem={({item}) => (
+          <RNTesterText style={styles.logLine}>
+            <RNTesterText
+              style={item.direction === 'sent' ? styles.sent : styles.received}>
+              {item.direction === 'sent' ? '↑ ' : '↓ '}
+            </RNTesterText>
+            {item.time} — {item.summary}
+          </RNTesterText>
+        )}
+      />
+    </View>
+  );
+}
+
+const styles = StyleSheet.create({
+  container: {
+    flex: 1,
+    padding: 16,
+  },
+  statusRow: {
+    flexDirection: 'row',
+    alignItems: 'center',
+    marginBottom: 8,
+  },
+  statusDot: {
+    width: 10,
+    height: 10,
+    borderRadius: 5,
+    marginRight: 6,
+  },
+  statusText: {
+    fontSize: 12,
+    fontWeight: '600',
+    letterSpacing: 0.5,
+  },
+  symbolLabel: {
+    fontSize: 14,
+  },
+  price: {
+    fontSize: 40,
+    fontWeight: '700',
+    marginBottom: 16,
+  },
+  symbolRow: {
+    flexDirection: 'row',
+    marginBottom: 16,
+  },
+  symbolButton: {
+    paddingVertical: 6,
+    paddingHorizontal: 14,
+    borderRadius: 16,
+    borderWidth: 1,
+    borderColor: '#cccccc',
+    marginRight: 8,
+  },
+  symbolButtonActive: {
+    backgroundColor: '#1e88e5',
+    borderColor: '#1e88e5',
+  },
+  symbolButtonText: {
+    fontSize: 13,
+  },
+  symbolButtonTextActive: {
+    color: '#ffffff',
+    fontWeight: '600',
+  },
+  controlsRow: {
+    flexDirection: 'row',
+    marginBottom: 16,
+  },
+  controlButton: {
+    paddingVertical: 8,
+    paddingHorizontal: 12,
+    backgroundColor: '#f0f0f0',
+    borderRadius: 6,
+    marginRight: 8,
+  },
+  controlButtonDisabled: {
+    opacity: 0.5,
+  },
+  controlButtonText: {
+    fontSize: 13,
+    fontWeight: '600',
+    color: '#333333',
+  },
+  logHeader: {
+    fontSize: 13,
+    fontWeight: '600',
+    marginBottom: 4,
+  },
+  log: {
+    flex: 1,
+    backgroundColor: '#fafafa',
+    borderRadius: 6,
+    padding: 8,
+  },
+  logLine: {
+    fontSize: 12,
+    fontFamily: 'Menlo',
+    marginBottom: 4,
+    color: '#333333',
+  },
+  sent: {
+    color: '#1e88e5',
+    fontWeight: '700',
+  },
+  received: {
+    color: '#2e7d32',
+    fontWeight: '700',
+  },
+});
+
+exports.title = 'WebSocket (Binance demo)';
+exports.category = 'Basic';
+exports.description =
+  'Live Binance trade ticker over a public WebSocket stream.';
+exports.examples = [
+  {
+    title: 'Binance live trade ticker',
+    render(): React.Node {
+      return <BinanceWebSocketDemo />;
+    },
+  },
+] as Array<RNTesterModuleExample>;
diff --git a/packages/rn-tester/js/utils/RNTesterList.android.js b/packages/rn-tester/js/utils/RNTesterList.android.js
@@ -356,6 +356,11 @@ const APIs: Array<RNTesterModuleInfo> = (
       category: 'Basic',
       module: require('../examples/Vibration/VibrationExample'),
     },
+    {
+      key: 'BinanceWebSocketDemo',
+      category: 'Basic',
+      module: require('../examples/WebSocket/BinanceWebSocketDemo'),
+    },
     {
       key: 'WebSocketExample',
       category: 'Basic',

diff --git a/packages/rn-tester/js/utils/RNTesterList.ios.js b/packages/rn-tester/js/utils/RNTesterList.ios.js
@@ -344,6 +344,10 @@ const APIs: Array<RNTesterModuleInfo> = (
       key: 'VibrationExample',
       module: require('../examples/Vibration/VibrationExample'),
     },
+    {
+      key: 'BinanceWebSocketDemo',
+      module: require('../examples/WebSocket/BinanceWebSocketDemo'),
+    },
     {
       key: 'WebSocketExample',
       module: require('../examples/WebSocket/WebSocketExample'),