Prevent nginx from killing idle tcp sockets - sockets

Question

I'm trying to use nginx as a reverse proxy for ssl/tcp sockets (so that I can write my server custom as raw tcp, but have nginx handle the ssl certificates). My use case requires the tcp connections remain alive, but to go idle (no packets back and forth) for extended periods of time (determined by the client, but as long as an hour). Unfortunately, nginx kills my socket connections after the first 10 minutes (timed to within a second) of inactivity, and I haven't been able to find either online or in the docs what actually controls this timeout.
I know that it has to be nginx doing it (not my raw server timing out, or my client's ssl socket), since I can directly connect to the server's raw tcp server without timeout issues, but if I run nginx as a raw tcp reverse proxy (no ssl) it does timeout.
Here's some code to reproduce the issue, note that I've commented out the ssl relevent pieces in nginx because the timeout occurs either way.
/etc/nginx/modules-enabled/test.conf:
stream {
upstream tcp-server {
server localhost:33445;
}
server {
listen 33446;
# listen 33446 ssl;
proxy_pass tcp-server;
# Certs
# ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
# ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;
}
}
server.js;
const net = require("net");
const s = net.createServer();
s.on("connection", (sock) => {
console.log('Got connection from', sock.remoteAddress, sock.remotePort );
sock.on("error", (err) => {
console.error(err)
clearInterval(i);
});
sock.on("close", () => {
console.log('lost connection from', sock.remoteAddress, sock.remotePort );
clearInterval(i);
});
});
s.listen(33445);
client.js
const net = require('net');
const host = 'example.com';
let use_tls = false;
let client;
let start = Date.now()
// Use me to circumvent nginx, and no timeout occurs
// let port = 33445;
// Use me to use nginx, and no timeouts occur after 10 mins of no RX/TX
let port = 33446;
client = new net.Socket();
client.connect({ port, host }, function() {
console.log('Connected via TCP');
// Include me, and nginx doesn't kill the socket
// setInterval(() => { client.write("ping") }, 5000);
});
client.on('end', function() {
console.log('Disconnected: ' + ((Date.now() - start)/1000/60) + " mins");
});
I've tried various directives in the nginx stream block, but nothing seems to help. Thanks in advance!