Reproducer for Websocket.close issue

Author: davidliu

packages/rn-tester/js/examples/Playground/RNTesterPlayground.js

@@ -12,14 +12,41 @@ import type {RNTesterModuleExample} from '../../types/RNTesterTypes';
 
 import RNTesterText from '../../components/RNTesterText';
 import * as React from 'react';
+import {useEffect, useState} from 'react';
 import {StyleSheet, View} from 'react-native';
 
+// Per the HTML spec, no 'message' event should fire once close() has been called.
+// echo.websocket.org greets each connection and echoes what it receives. The 
+// websocket here is immediately closed, so replies arrive while the socket is 
+// no longer in the OPEN state.
+// 
+// On React-Native, the following code logs the greeting and echoed hello after close.
+// On browsers, the equivalent code won't log any messages.
+
 function Playground() {
+  const [log, setLog] = useState<Array<string>>([]);
+
+  useEffect(() => {
+    const add = (s: string) => {
+      console.log(s);
+      setLog(l => [...l, s]);
+    };
+    const ws = new WebSocket('wss://echo.websocket.org');
+    ws.onopen = () => {
+      ws.send('hello');
+      ws.close();
+      add(`close() called, readyState=${ws.readyState}`);
+    };
+    ws.onmessage = e =>
+      add(
+        `message after close(): "${String(e.data)}", readyState=${ws.readyState}`,
+      );
+    ws.onclose = e => add(`onclose code=${String(e.code)}`);
+  }, []);
+
   return (
     <View style={styles.container}>
-      <RNTesterText>
-        Edit "RNTesterPlayground.js" to change this file
-      </RNTesterText>
+      <RNTesterText>{log.join('\n')}</RNTesterText>
     </View>
   );
 }