<uses-permission android:name="android.permission.INTERNET" />

private class NetworkTask extends AsyncTask<Void, Void, Void> {
    @Override
    protected Void doInBackground(Void... voids) {
        // 在这里执行网络操作
        try {
            Socket socket = new Socket("example.com", 8080);
            // 处理socket
            socket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
}

<network-security-config>
    <domain-config cleartextTrafficPermitted="true">
        <domain includeSubdomains="true">example.com</domain>
    </domain-config>
</network-security-config>

<application
    android:networkSecurityConfig="@xml/network_security_config"
    ... >

ConnectivityManager cm = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
boolean isConnected = activeNetwork != null && activeNetwork.isConnectedOrConnecting();

StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder()
    .detectAll()
    .penaltyLog()
    .build());