You can configure a Static IP for that machine and you can add specific MAC addresses to some routers, in order to share specific services or IP informatrion. Adding the MAC address to a router, is normally used for Wireless, to limit the access of Wifi, or to limite the access of admin-panel-login-page.

For what I can understand, you only need to configure a static IP for your NodeJS server.

If you setup your machine to use that IP, your router "reserv" that IP for that machine, which means, the DHCP service will not attribute that IP to another device.