Outgoing UDP connection not working

Posted May 11, 2017 5.1k views
NginxPHPNetworkingFirewallLEMPUbuntu 16.04

I have a small app that uses UDP to make a connection to another host and it simply doesn’t return anything.

Locally the app works just fine, when deployed to a VPS though…

I’ve tried to disable the entire firewall but that did not work as well.

What are the chances of DO block outgoing UDP connections? (some times they can be a Ddos, so maybe there is a block?)

  • @jtittle sorry to bother you, but is this your area of expertise?


  • Same here, I am unable to continue making my game since I have tried and failed several times now to get a two way connection between udp client and host on digital ocean. I dont know why but It seems i can only get msg from client but cant send respond from digital ocean server.

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2 answers


The only ports that DigitalOcean typically blocks on new accounts are mail ports to prevent spam since it’s so easy to setup an account and fund it. Once the account is verified, that can be lifted.

To my knowledge, no other ports are blocked, though to confirm that you’d need to submit a ticket to the support team.

What specifically is the application and what port are they trying to connect on?

  • its a Web Rcon app that I’m developing for an old quake3 engine game, its accepts connection via UDP on port 29070.

    Locally it works just fine just like I’ve said, once deployed to DO it doesn’t return data.

    And debbuging UDP is #$#@ cause it doesn’t “establish” a connection.

I faced this same problem. The problem was in sending UDP packets from the server with the wrong source port. If the client is behind NAT, then destination port of packets to server and source port of packets from server should be the same.

You can check UDP packages with command:
tcpdump udp

The problem was in the server code.