nginx use of UDP ports?

[Vadim Grinshpun]

Hello,

After setting up nginx to run, I've noticed that 'lsof' shows all nginx
processes (master + workers) listening on an ephemeral UDP port.

    nginx 25142   vgrinshp    4u  IPv4 422450236      0t0  UDP
    127.0.0.1:33226
    nginx 25144   vgrinshp    4u  IPv4 422450236      0t0  UDP
    127.0.0.1:33226
    nginx 25145   vgrinshp    4u  IPv4 422450236      0t0  UDP
    127.0.0.1:33226
    nginx 25146   vgrinshp    4u  IPv4 422450236      0t0  UDP
    127.0.0.1:33226
    nginx 25147   vgrinshp    4u  IPv4 422450236      0t0  UDP
    127.0.0.1:33226


I did not explicitly configure anything that (AFAIK) uses UDP, and I
could not find anything in the doc that mentions any use of UDP ports by
nginx.
The ports seem to be used by nginx even with the most minimal nginx.conf.

Does anyone here know how/why these ports are used?

Thanks for any info!
-Vadim



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