react-native-navigation/scripts/start.js

const exec = require('shell-utils').exec;

run();

function run() {
  const port = findPort();
  exec.execSync(`watchman watch-del-all || true`);
  exec.execSync(`adb reverse tcp:${port} tcp:${port} || true`);
  exec.execSync(`node ./node_modules/react-native/local-cli/cli.js start --port=${port} --root=./playground`);
}

function findPort() {
  let port = 8081;
  if (!process.env.CI) {
    return port;
  }
  while (!isPortOpen(port)) {
    port = Number((Math.random() * 1000).toFixed(0)) + 35000;
  }
  return port;
}

function isPortOpen(port) {
  try {
    return !exec.execSyncRead(`netstat -vanp tcp | grep ${port}`);
  } catch (e) {
    return true;
  }
}