2. Find NodeMCU on your Local Net

A good tool for scanning mac addresses on your local network is arp-scan. Install it by running

brew install arp-scan

Then you can call

arp-scan --localnet

to get all mac addresses into arp cache. To separate those that belong to Espressif (maker of esp8266 MCU that will show up on your local network) you can run this:

arp -a | grep -e "54:5a:a6" -e "24:a:c4" -e "a0:20:a6" -e "90:97:d5" -e "18:fe:34" -e "60:1:94" -e "5c:cf:7f" -e "ac:d0:74" -e "30:ae:a4"

What will that do is get all local network mac addresses and scan for those with prefixes that belong to Espressif

Success test

$ arp-scan --localnet
Interface: en0, datalink type: EN10MB (Ethernet)
Starting arp-scan 1.9 with 256 hosts (http://www.nta-monitor.com/tools/arp-scan/)    34:12:98:00:69:35    (Unknown)    00:17:88:23:40:91    Philips Lighting BV    00:0e:58:14:52:b1    Sonos, Inc.    5c:aa:fd:23:7b:71    (Unknown)    60:f4:45:71:0f:61    (Unknown)    00:24:e4:25:26:d2    Withings    6c:40:08:aa:9c:c3    (Unknown)    a0:02:dc:9b:a5:a5    (Unknown)    c8:69:cd:19:e1:c6    (Unknown)    b4:18:d1:ee:b6:b1    (Unknown)    f8:27:93:a1:d0:d1    (Unknown)    78:4b:87:a4:c6:b1    (Unknown)    5c:cf:7f:16:c4:01    (Unknown)    58:1f:aa:db:a5:e1    Apple, Inc.    5c:93:a2:13:d9:d5    (Unknown)    b8:27:eb:d6:d7:f4    Raspberry Pi Foundation    a0:20:a6:02:68:73    (Unknown)    5c:cf:7f:95:12:d2    (Unknown)    a0:20:a6:01:49:a1    (Unknown)

$ arp -a | grep -e "54:5a:a6" -e "24:a:c4" -e "a0:20:a6" -e "90:97:d5" -e "18:fe:34" -e "60:1:94" -e "5c:cf:7f" -e "ac:d0:74" -e "30:ae:a4"
? ( at 5c:cf:7f:16:c4:c on en1 ifscope [ethernet]
? ( at a0:20:a6:1:49:a6 on en1 ifscope [ethernet]
? ( at a0:20:a6:2:68:17 on en1 ifscope [ethernet]
? ( at 5c:cf:7f:95:12:a8 on en1 ifscope [ethernet]

Have fun!