Question

Using DO Apps, how to open TCP port?

Posted on December 15, 2023
DigitalOcean App Platform
Asked by Will Belden

Trying to expose a TCP port for a node-red flow for some colleagues. This should be dead simple. The port I’m trying to open is 3333. Port 80 seems to auto-map to the typical http port 1800 and I can access the standard web editor via port 80. I tried this internal_ports you see at the bottom, but that isn’t working:

alerts:
- rule: DEPLOYMENT_FAILED
- rule: DOMAIN_FAILED
features:
- buildpack-stack=ubuntu-22
ingress:
  rules:
  - component:
      name: nodered-node-red
    match:
      path:
        prefix: /
name: scalesim
region: nyc
services:
- http_port: 8080
  image:
    registry: nodered
    registry_type: DOCKER_HUB
    repository: node-red
    tag: latest
  instance_count: 1
  instance_size_slug: basic-xxs
  internal_ports:
  - 3333
  name: nodered-node-red

Can someone advise how I might change this App Spec so that I can test the 3333 TCP port listener in my flow?

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Bobby Iliev

Site Moderator

• December 15, 2023

Accepted Answer

Hey Will,

I see you’re looking to expose 3333 as TCP port for your Node-RED flow on the DigitalOcean App Platform. Based on the current capabilities of the App Platform, there are a few key points to consider:

The http_port field in your app specification determines the internal port that your service’s run command listens on. This is typically geared towards HTTP traffic. If you don’t set a PORT environment variable, the App Platform automatically uses the value of http_port.
The internal_ports array you mentioned is intended for internal traffic within your application. These ports are used for communication between services within your app and are not exposed externally. Ports defined in internal_ports field can accommodate any TCP-based traffic.
For routing external HTTP traffic to your service, you’ll use the ingress rules in your app spec. This is where you define how HTTP requests are directed to your service components. However, this is specifically for HTTP/HTTPS traffic and not for arbitrary TCP ports.

Given these constraints, if your application requires a direct exposure of a TCP connection on port 3333 that can’t be adapted to HTTP/WebSockets, you might find the App Platform limiting for this specific use case. In this scenario, a DigitalOcean Droplet could be a better fit. Droplets provide more flexibility in terms of network configurations, allowing direct management of TCP ports.

Hope that this helps!

Best,

Bobby