Nodejs app running on localhost:3000 is not accessible on Linux server - node.js

Question

I want to deploy my web app on cloud server, the OS is Centos 7, I got a static IP address like "34.80.XXX.XX", if I set my web app running on port 80, and I can see the page when I enter "34.80.XXX.XX:80".
But I if I running on port 3000, and enter "34.80.XXX.XX:3000", it not working.
I have tried to stop my firewall:
# systemctl stop firewalld
And use the command below to check there is no other program running on port 3000
# netstat -tnlp
Here is the code in app.js
const Koa = require('koa')
const json = require('koa-json')
const app = new Koa()
const PORT = 3000
// make JSON Prettier middleware
app.use(json())
// Simple middleware example
app.use(async ctx => {
ctx.body = {msg: 'Hello World'}
})
app.listen(PORT)
console.log(`server run at http://localhost:${PORT}`)
I use pm2 to run it in background
[root#instance-1 01-hello]# pm2 start app.js -n hello
[PM2] Starting /home/xing/01-hello/app.js in fork_mode (1 instance)
[PM2] Done.
┌─────┬──────────┬─────────────┬─────────┬─────────┬──────────┬────────┬──────┬───────────┬──────────┬──────────┬──────────┬──────────┐
│ id │ name │ namespace │ version │ mode │ pid │ uptime │ ↺ │ status │ cpu │ mem │ user │ watching │
├─────┼──────────┼─────────────┼─────────┼─────────┼──────────┼────────┼──────┼───────────┼──────────┼──────────┼──────────┼──────────┤
│ 0 │ hello │ default │ N/A │ fork │ 3835 │ 0s │ 0 │ online │ 0% │ 12.6mb │ root │ disabled │
└─────┴──────────┴─────────────┴─────────┴─────────┴──────────┴────────┴──────┴───────────┴──────────┴──────────┴──────────┴──────────┘
And I enter the command netstat -tnlp to check app.js is running on port 3000
[root#instance-1 01-hello]# netstat -tnlp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 15958/sshd
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 1184/master
tcp 0 0 127.0.0.1:27017 0.0.0.0:* LISTEN 2421/mongod
tcp6 0 0 :::22 :::* LISTEN 15958/sshd
tcp6 0 0 :::3000 :::* LISTEN 3835/node /home/xin
tcp6 0 0 ::1:25 :::* LISTEN 1184/master
I have stuck on this point for long time, is there any good solution