Why are Bitcoin core peers on ports other than 8333?

[Shackalacka]

Hello, I'm just curious if this is normal.  I've had a bit of trouble finding out through searching.  Bitcoin core is connecting to peers on ports other than 8333.  I've only opened port 8333 on my router.

Bitcoin Client Software and Version Number: Bitcoin Core version v0.15.0.1 (64-bit)
Operating System: Windows 10 Home 64 Bit
System Hardware Specs: AMD Ryzen 1700X, 16GB Ram, SSD and HD
Description of Problem: Bitcoin core is crashing with DB corruption errors while syncing blockchain.  Assuming HD hardware error, but investigating possible system compromise
Any Related Addresses: N/A
Any Related Transaction IDs: N/A
Screenshot of the problem: https://imgur.com/a/3GyXh
Log Files from the Bitcoin Client:

[1715109380]

1715109380

[1715109380]

1715109380

[jackg]

8333 is the default port and is the one your node uses to transmit data.

If someone else has a node configured to use say port number 1200 as their 8333 could have a NAS drive or a server going through it. Then your data would go: bitcoin-qt --> yourip:8333 --> theirip:1200 -->  theirnode.

So you're still using your 8333 port on your router but they're using another port and your core client is just adapting to it.

[Shackalacka]

Awesome, thanks for the reply!

[RGBKey]

To give some more background on this, I run a full node but I route my traffic through a VPN. This VPN allows me to forward ports, but not specific ports, so I'm just given a random port number that I can use to be connectable from the outside Internet. This is the port I run my full node off of, so it's not standard but it's how I get it to be reachable.

Just another reason you might see someone using a non-standard port.

[Shackalacka]

That's great, interesting to note that about half my peers are doing this.  Sometimes more, sometimes less.