Why only 14000 reachable nodes on bitcoin network?

[Aikido123]

Hi there,
New bitcoiner here.  (Is that what we call ourselves?).  My number one question right now in trying to understand everything is: how come there aren't more nodes on this network.  Out of the 150 million or so, that own bitcoin, why wouldn't there be more nodes running it.  I would think 50,000 or so would be a reasonable number to expect given the number of computer geeks and hobbyists in the space.  Also, it's pretty easy to do so if one is interested.  Are there more nodes behind firewalls and other hidden places where they are not being counted?  If so, what is that estimate? What am I missing?

[1713431375]

1713431375

[BlackHatCoiner]

While bitnodes.io says there are 14 thousands reachable nodes, luke.dashjr.org has another opinion. (It says 50 thousands)

The former probably excludes those that don't accept incoming connections. I can't think of another reasonable explanation. Yeah, IMO there are more than just 14,000.

Edit: Yep, I'm right:

There are 10987 full nodes according to bitnodes,

those are only reachable nodes, the majority of bitcoin nodes (90%) are not reachable or in other words don't accept incoming connections hence they are not listed on sites like bitnodes. take a look here: https://luke.dashjr.org/programs/bitcoin/files/charts/historical.html

[Aikido123]

Ok, that makes sense.
Follow up: Why would nodes be 'Unreachable'.  Don't they need to be reachable in order to participate in validating blocks?  Or what does unreachable mean?

[BlackHatCoiner]

Follow up: Why would nodes be 'Unreachable'.  Don't they need to be reachable in order to participate in validating blocks?  Or what does unreachable mean?

Great question. Short answer: No.

Long answer: Unreachable means they don't allow incoming connections. Now, what does that mean. Bitcoin Core, by default, allows up to 125 connections to different peers 10 of which are outbound. The non-listening nodes (those that only accept outbound connections) can establish up to 8 full-relay connections with up to 8 listening nodes (the ones that do accept incoming connections).

Both non-listening and listening nodes contribute to the network by sharing data, but they each have different traffic consumption. For instance, a non-listening node will communicate with only 8 listening nodes while listening nodes can have up to 115 incoming connections.

They all validate blocks normally. They all share blocks with each other. Running a listening node is just a greater contribution to the network  bandwidth-wise.