Connecting EspruinoWiFi to computer over WiFi

I know the IP of my computer, but when I try

        require("http").get('http://192.168.0.5:3000', function(res) {
            res.on('data', function(d) {
                console.log("--->"+d);
            });
        }).on('error', function(e) {
            console.log(' --- ERROR: ', e)
        });

it shows the error

 --- ERROR:  { "code": -15,
  "message": "no response"
 }

But I can access http://192.168.0.5:3000 on my desktop browser.

Any thoughts on why Espruino might not be able to access it?

EDIT: hmm, I can access the Espruino if I know it's IP:

┌─[00:41:15/localhost/chronos/.../src/trusktr+trusktr.io]
└─╼ ping 192.168.0.8
PING 192.168.0.8 (192.168.0.8) 56(84) bytes of data.
64 bytes from 192.168.0.8: icmp_seq=1 ttl=255 time=15.1 ms
64 bytes from 192.168.0.8: icmp_seq=2 ttl=255 time=35.6 ms
64 bytes from 192.168.0.8: icmp_seq=3 ttl=255 time=61.1 ms

Is there a way to make Espruino's IP static?