<p>If you don't want to, you don't have to open ports at all. You'll still have a full node, it will just have fewer connections. Full nodes usually make 8 outgoing connections and can have many more incoming if you have the port open (for a total of 125 by default). Incoming connections can also be SPV (phone) wallets, or other full nodes.</p>

<p>So the benefit is that you're helping out the network a little bit more providing connection opportunities and bandwidth to more other full and non-full nodes. There's not really a shortage at the moment though.</p>

<p>Typically only the first time when you run the software it might do a DNS lookup on the domains you mention. Each name represents dozens of IP addresses of random other full nodes (not just nodes run by those people). Once your node has a connection to a few peers, it will learn new IP addresses from those, maintaining its own list of IP addresses which is stored when you close the software shuts down.</p>

CC BY-SA 3.0
2017-11-05T22:52:25.457Z
2017-11-05T22:52:25.457Z
Jannes
<p>I am running a bitcoin core (v0.15.01) full node according to <a href="https://bitcoin.org/en/full-node" rel="noreferrer">https://bitcoin.org/en/full-node</a>. They say </p>

<blockquote>
  <p>"To support the Bitcoin network, you also need to allow incoming
  connections."</p>
</blockquote>

<p>I hesitate opening ports because having a port open for incoming connection allows for anyone to connect. <strong>So is this really necessary for bitcoin to work?</strong> They to not explicitly state what kind of support this enables.</p>

<p>I see that the client already makes connections to various domains like</p>

<pre><code>x9.dnsseed.bluematt.me
x9.seed.bitcoinstats.com
dnsseed.bitcoin.dashjr.org
x9.seed.bitcoin.sipa.be
x9.seed.btc.petertodd.org
x9.seed.bitcoin.jonasschnelli.ch
</code></pre>

<p>Do these represent the "distributed" properties of Bitcoin? Why are there not more of them? Or is this completely unrelated?</p>

<p>Note: I have read questions like <a href="https://bitcoin.stackexchange.com/questions/40953/how-to-trigger-port-for-bitcoin-client-e-g-8333">this one</a> or <a href="https://bitcoin.stackexchange.com/questions/61546/what-is-the-nat-traversal-technique-used-by-bitcoin">this one</a>, but they more focus on the how to, than what the benefit actually is.</p>

<bitcoin-core><network><port>
What is the benefit of opening port 8333 to a client?
nulldev
# What is the benefit of opening port 8333 to a client?

(Asked by: username_0 on 2017-11-05)

I am running a bitcoin core (v0.15.01) full node according to <https://bitcoin.org/en/full-node>. They say

> "To support the Bitcoin network, you also need to allow incoming
> connections."

I hesitate opening ports because having a port open for incoming connection allows for anyone to connect. **So is this really necessary for bitcoin to work?** They to not explicitly state what kind of support this enables.

I see that the client already makes connections to various domains like

```
x9.dnsseed.bluematt.me
x9.seed.bitcoinstats.com
dnsseed.bitcoin.dashjr.org
x9.seed.bitcoin.sipa.be
x9.seed.btc.petertodd.org
x9.seed.bitcoin.jonasschnelli.ch

```

Do these represent the "distributed" properties of Bitcoin? Why are there not more of them? Or is this completely unrelated?

Note: I have read questions like [this one](https://bitcoin.stackexchange.com/questions/40953/how-to-trigger-port-for-bitcoin-client-e-g-8333) or [this one](https://bitcoin.stackexchange.com/questions/61546/what-is-the-nat-traversal-technique-used-by-bitcoin), but they more focus on the how to, than what the benefit actually is.

**Tags:** bitcoin-core, network, port


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## 1 answers

### Answer by username_1 on 2017-11-05. Score: 6 | Accepted answer

If you don't want to, you don't have to open ports at all. You'll still have a full node, it will just have fewer connections. Full nodes usually make 8 outgoing connections and can have many more incoming if you have the port open (for a total of 125 by default). Incoming connections can also be SPV (phone) wallets, or other full nodes.

So the benefit is that you're helping out the network a little bit more providing connection opportunities and bandwidth to more other full and non-full nodes. There's not really a shortage at the moment though.

Typically only the first time when you run the software it might do a DNS lookup on the domains you mention. Each name represents dozens of IP addresses of random other full nodes (not just nodes run by those people). Once your node has a connection to a few peers, it will learn new IP addresses from those, maintaining its own list of IP addresses which is stored when you close the software shuts down.


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