root@sysdba:~$ gcloud compute firewall-rules list
NAME                   NETWORK SRC_RANGES    RULES                        SRC_TAGS TARGET_TAGS
allow-agent            default 0.0.0.0/0     tcp:3872
allow-bipub            default 0.0.0.0/0     tcp:9803
allow-oms              default 0.0.0.0/0     tcp:7803
allow-ons              default 0.0.0.0/0     tcp:2016
allow-tns              default 0.0.0.0/0     tcp:1521
default-allow-http     default 0.0.0.0/0     tcp:80                                http-server
default-allow-https    default 0.0.0.0/0     tcp:443                               https-server
default-allow-icmp     default 0.0.0.0/0     icmp
default-allow-internal default 10.240.0.0/16 tcp:0-65535,udp:0-65535,icmp
default-allow-rdp      default 0.0.0.0/0     tcp:3389
default-allow-ssh      default 0.0.0.0/0     tcp:22

root@sysdba:~$ nmap -A em13c -p 1521-1522
Starting Nmap 6.47 ( http://nmap.org ) at 2016-01-20 10:25 EST
Nmap scan report for em13c (xxx.xxx.xx.xx)
Host is up (0.037s latency).
PORT     STATE    SERVICE    VERSION
1521/tcp open     oracle-tns Oracle TNS Listener
1522/tcp filtered rna-lm
Service detection performed. Please report any incorrect results at http://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 7.55 seconds

root@sysdba:~$ gcloud compute firewall-rules update allow-tns --allow tcp:1521-1522
Updated [https://www.googleapis.com/compute/v1/projects/sysdba/global/firewalls/allow-tns].

root@sysdba:~$ gcloud compute firewall-rules list
NAME                   NETWORK SRC_RANGES    RULES                        SRC_TAGS TARGET_TAGS
allow-agent            default 0.0.0.0/0     tcp:3872
allow-bipub            default 0.0.0.0/0     tcp:9803
allow-oms              default 0.0.0.0/0     tcp:7803
allow-ons              default 0.0.0.0/0     tcp:2016
allow-tns              default 0.0.0.0/0     tcp:1521-1522
default-allow-http     default 0.0.0.0/0     tcp:80                                http-server
default-allow-https    default 0.0.0.0/0     tcp:443                               https-server
default-allow-icmp     default 0.0.0.0/0     icmp
default-allow-internal default 10.240.0.0/16 tcp:0-65535,udp:0-65535,icmp
default-allow-rdp      default 0.0.0.0/0     tcp:3389
default-allow-ssh      default 0.0.0.0/0     tcp:22

root@sysdba:~$ nmap -A em13c -p 1521-1522
Starting Nmap 6.47 ( http://nmap.org ) at 2016-01-20 10:24 EST
Nmap scan report for em13c (xxx.xxx.xx.xx)
Host is up (0.037s latency).
PORT     STATE SERVICE    VERSION
1521/tcp open  oracle-tns Oracle TNS Listener
1522/tcp open  oracle-tns Oracle TNS Listener
Service detection performed. Please report any incorrect results at http://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 6.35 seconds