I agree with skipping UDP.

I think what IANA is doing is "reserving" the port number in a way, and
not really forcing the point that the only possible service in the future
will be a TCP vs UDP similar.

Stuart Henderson <stu@spacehopper.org> wrote:

> On 2025/04/23 15:29, Hugo Osvaldo Barrera wrote:
> > Port 1883 is used for plain-text mqtt and 8883 is used for TLS+mqtt.
> > See: https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=mqtt
> 
> Many IANA registrations are for both TCP and UDP although nany
> protocols never or rarely run over both. We typically only list a
> port/protocol if in very common usage.
> 
> I agree with adding MQTT over TCP, this is a common protocol and
> reserving this port to prevent it being used in the dynamic range, which
> is a side-effect of listing in services(5), makes sense.
> 
> I think we should skip UDP.
> 
> 
> > Please CC me in replies; I am not subscribed to this list.
> > 
> > -- 
> > Hugo
> 
> > diff --git etc/services etc/services
> > index 0405aa38d42..7f8c6143e9c 100644
> > --- etc/services
> > +++ etc/services
> > @@ -190,6 +190,8 @@ pptp		1723/tcp			# Point-to-Point Tunneling Protocol
> >  pptp		1723/udp			# Point-to-Point Tunneling Protocol
> >  radius		1812/udp			# radius authentication
> >  radacct		1813/udp	radius-acct	# radius accounting
> > +mqtt		1883/tcp			# Message Queuing Telemetry Transport Protocol
> > +mqtt		1883/udp			# Message Queuing Telemetry Transport Protocol
> >  ssdp		1900/tcp			# SSDP
> >  ssdp		1900/udp			# SSDP
> >  nfsd		2049/udp	nfs		# NFS server
> > @@ -275,6 +277,8 @@ afs3-rmtsys	7009/tcp			# AFS remote cache manager service
> >  afs3-rmtsys	7009/udp			# AFS remote cache manager service
> >  puppet		8140/tcp			# Puppet master service
> >  matrix-fed	8448/tcp			# Matrix Federation Protocol
> > +secure-mqtt	8883/tcp			# Secure MQTT
> > +secure-mqtt	8883/udp			# Secure MQTT
> >  ub-dns-control	8953/tcp			# unbound dns nameserver control
> >  git		9418/tcp			# git pack transfer service
> >  git		9418/udp			# git pack transfer service
>