Function startServer

packages/react-devtools-core/src/standalone.js:309–402

(
  port: number = 8097,
  host: string = 'localhost',
  httpsOptions?: ServerOptions,
  loggerOptions?: LoggerOptions,
)

};

function startServer(
  port: number = 8097,
  host: string = 'localhost',
  httpsOptions?: ServerOptions,
  loggerOptions?: LoggerOptions,
): {close(): void} {
  registerDevToolsEventLogger(loggerOptions?.surface ?? 'standalone');

  const useHttps = !!httpsOptions;
  const httpServer = useHttps
    ? require('https').createServer(httpsOptions)
    : require('http').createServer();
  const server = new Server({server: httpServer, maxPayload: 1e9});
  let connected: WebSocket | null = null;
  server.on('connection', (socket: WebSocket) => {
    if (connected !== null) {
      connected.close();
      log.warn(
        'Only one connection allowed at a time.',
        'Closing the previous connection',
      );
    }
    connected = socket;
    socket.onerror = error => {
      connected = null;
      onDisconnected();
      log.error('Error with websocket connection', error);
    };
    socket.onclose = () => {
      connected = null;
      onDisconnected();
      log('Connection to RN closed');
    };
    initialize(socket);
  });

  server.on('error', (event: $FlowFixMe) => {
    onError(event);
    log.error('Failed to start the DevTools server', event);
    startServerTimeoutID = setTimeout(() => startServer(port), 1000);
  });

  httpServer.on('request', (request: $FlowFixMe, response: $FlowFixMe) => {
    // Serve a file that immediately sets up the connection.
    const backendFile = readFileSync(join(__dirname, 'backend.js'));

    // The renderer interface doesn't read saved component filters directly,
    // because they are generally stored in localStorage within the context of the extension.
    // Because of this it relies on the extension to pass filters, so include them wth the response here.
    // This will ensure that saved filters are shared across different web pages.
    const savedPreferencesString = `
      window.__REACT_DEVTOOLS_COMPONENT_FILTERS__ = ${JSON.stringify(
        getSavedComponentFilters(),
      )};`;

    response.end(
      savedPreferencesString +
        '\n;' +