Yes, the sketch is not using DHCP, so you need to set the IP address. It should be on the same subnet as your existing machines, so the first three numbers should be the same (192,168,1) and the last number needs to be unique on your network, and preferable outside your router's DHCP scope. I would try
IPAddress ip(192,168,1, 99);
unless you already have 99 machines on your network.