Trouble getting UDP to work

Questions / Help
3

Ok, so I did this:

FROM alpine
RUN apk update && apk add nmap-ncat net-tools tcpdump bind-tools
CMD tail -f /dev/null

I ran flyctl launch, and then edited the fly.toml to include:

[[services]]
  internal_port = 10000
  protocol = "udp"
  [[services.ports]]
    port = "10000"

[[services]]
  internal_port = 5000
  protocol = "udp"
  [[services.ports]]
    port = "5000"

(Just in case it was port-specific behavior).

I deployed, then I flyctl ssh console'd into the instance.

I ran ncat -u -4 -v -l -c cat -k fly-global-services 10000, then, from my desktop, I ran nc -u <myapp>.fly.dev (nc is the one true netcat).

It worked; here’s a transcript:

Client:

> $ nc -u testapp.fly.dev 10000                                                                                                                         
helu
helu

Server:

/ # ncat -u -4 -v -l -c cat -k fly-global-services 10000
Ncat: Version 7.91 ( https://nmap.org/ncat )
Ncat: Listening on 172.19.2.243:10000
Ncat: Connection from 50.205.163.67.
Ncat: Listening on 172.19.2.243:10000