Connect to external IP address

Posted on April 7, 2021

By michaelrbraun1985

Hi everyone, for some reason my node.js app is not able to connect to an IP address after I deployed it to digital ocean. My app is supposed to connect to physical alarm systems via IP/Port to get the system status (armed/disarmed). UFW is currently inactive. My app is working locally. Is there something I need to configure in order to get it to connect from the digital ocean servers?

const client = new ElkClient({
    connection: { 
      host: "IP/DNS ADDRESS",
      secure: true/false,
      port: PORT,
      site: "SITENAME"
    }
  })

  console.log(client)
  client.connect().catch((err)=> console.log("Connection Error"))

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KFSys

April 7, 2021

Hi @michaelrbraun1985,

You can try and allow the port through your IPtables. I believe it will still need to be edited even if you are not using UFW.

First to allow incoming connections from this port (only if needed):

sudo iptables -A INPUT -p tcp --dport XXX -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT
sudo iptables -A OUTPUT -p tcp --sport XXX -m conntrack --ctstate ESTABLISHED -j ACCEPT

Where you’ll need to change XXX with your actual port.

Now for outgoing connections, you’ll need to execute the following:

sudo iptables -A OUTPUT -p tcp --dport XXX -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT
sudo iptables -A INPUT -p tcp --sport XXX -m conntrack --ctstate ESTABLISHED -j ACCEPT