localhost, 127.0.0.1 does not work between 2 containers in a kubernetes node - node.js

Question

I have 2 containers in a Kubernetes node.
microk8s kubectl exec -it worker-statefulset-name-0 -c worker-container bash
To connect to the first. It is a python container with a socket interface, not http. Observe the IP address
python
>>> import socket
>>> socket.gethostbyname(socket.gethostname())
'10.1.56.41'
The second is a nodejs container. Opening a socket between these 2 containers works as expected when using the ip address:
microk8s kubectl exec -it worker-statefulset-name-0 -c worker-health-monitor bash
nodejs
socket_utilities.promise_open_socket_send_get_ack('10.1.56.41', 55001, data)
.then((result)=>{console.log(result)})
> { result: 'got work' }
but fails if I use localhost or 127.0.0.1
socket_utilities.promise_open_socket_send_get_ack('127.0.0.1', 55001, data).then((result)=>{console.log(result)})
> 1661547443715ECONNREFUSED
(node:21) UnhandledPromiseRejectionWarning: Error: connect ECONNREFUSED 127.0.0.1:55001
> socket_utilities.promise_open_socket_send_get_ack('localhost', 55001, data).then((result)=>{console.log(result)})
> 1661547509627ECONNREFUSED
(node:21) UnhandledPromiseRejectionWarning: Error: connect ECONNREFUSED 127.0.0.1:55001
The promise_open_socket_send_get_act is simply a wrapper around net.createConnection
function promise_open_socket_send_get_ack(host, port, data) {
return new Promise((resolve, reject) => {
try {
//console.log("createConnection host=" + host + ", port:" + port + ", my ip is " + get_my_IPv4_addresses())
const client = net.createConnection({ host: host, port: port })
let data_from_server = null
let to = null
client.on("error", (e) => {
if (e.errno == "ECONNREFUSED") {
console.log(new Date().getTime()+"ECONNREFUSED")
}
clearTimeout(to)
reject(e)
})
....
I know the nodejs container is on the same node as the python container. They are created as part of the same StatefulSet, but to be sure:
> socket_utilities.get_my_IPv4_addresses()
[ '10.1.56.41', eth0: [] ]
function get_my_IPv4_addresses(){
const nets = os.networkInterfaces();
const results = []
for (const name of Object.keys(nets)) {
for (const net of nets[name]) {
// Skip over non-IPv4 and internal (i.e. 127.0.0.1) addresses
if (net.family === 'IPv4' && !net.internal) {
if (!results[name]) {
results[name] = [];
}
results.push(net.address);
}
}
}
return results
}
So a kludgy solution is to use get_my_IPv4_addresses and open the socket with this.
Aside from being kludgy, I fear I do not understand something and will run into problems in the future.
So how do I get 127.0.0.1 to work correctly in a kubernetes nodejs container?