I’ve successfully been able to run a UDP DNS server on port 53. However, when I try to run a DNS server on TCP port 53 I get the following error:
$ flyctl deploy Deploying <myapp> ==> Validating App Configuration *** ✘ services.0.ports.0.port: must be one of: [80, 443, 5000, 10000..10100] Error App configuration is not valid
According to App Configuration (fly.toml) · Fly it looks like 53 is indeed not a valid public TCP port, but can that limitation be lifted so that I can run a TCP DNS server?
The use case for using TCP for DNS is to e.g. return TXT or DNSSEC responses that can’t fit into a UDP packet.
FWIW my config file is:
app = "<myapp>" kill_signal = "SIGINT" kill_timeout = 5 [[services]] internal_port = 53 protocol = "tcp" [[services.ports]] port = "53"