I have 2 VMs in the same "default" GCloud network: vm1 and vm2.
Inside vm1, I can:
vm1:~$ curl localhost:5984
{"couchdb":"Welcome","uuid":"121d13a07f68","version":"1.6.0","vendor":{"version":"16.10","name":"Ubuntu"}}
Inside vm2, I can:
vm2:~$ curl vm1-name
<html>
<head><title>301 Moved Permanently</title></head>
<body bgcolor="white">
<center><h1>301 Moved Permanently</h1></center>
<hr><center>nginx/1.10.1 (Ubuntu)</center>
</body>
</html>
But when I try to reach the 5984 port in vm1, I get:
vm2:~$ curl vm1-name:5984
curl: (7) Failed connect to vm1-name:5984; Connection refused
GCP adds a firewall rulle that let ingress all tcp:0-65535 traffic, so I don't understand what is going on here.