Question
Outgoing UDP connection not working
- Posted on May 11, 2017
- LEMPNginxNetworkingPHPFirewallUbuntu 16.04
Asked by Vanker
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?)
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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.
@Vanker
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?