structure of communicating with bitcoin DNSs to get list of nodes

Question

I want to communicate with bitcoin DNSs to get list of bitcoin nodes.

for now I want some example and structure of messages between I and bitcoin DNS.

I found two DNS names:

dnsseed.bluematt.me
dnsseed.bitcoin.bit

and want communicate with them.

please help me

Answer 1

"Bitcoin DNS" is a bit of a misnomer.

It appears that hostnames such as dnsseed.bluematt.me are not actual DNS servers - you cannot communicate with them using DNS protocols. However they are valid domain names in the normal public Internet DNS system and have multiple "A" records associated with them. You can therefore query the DNS seed hostnames in the normal way (i.e. send DNS queries to your local DNS servers) to get a list of IP addresses that are presumably Bitcoin full-nodes.

You can then, I guess, communicate with any of those IP-addresses using the appropriate Bitcoin peer-to-peer protocols.

Note that some of the returned addresses are IPv6 and some IPv4.

C:\> nslookup dnsseed.bluematt.me
Server:  xxxxxxxxxxxx
Address:  192.168.1.nnn

Non-authoritative answer:
Name:    dnsseed.bluematt.me
Addresses:  2607:fea8:80a0:a1f:b1dc:86a4:62a1:ff7d
          2001:0:9d38:6ab8:1c01:270:bff9:f75a
          2a01:4f8:c0:1328::2
          2a01:4f8:171:d4a::2
          2002:bc7c:110::bc7c:110
          2001:41d0:d:221d::
          2a02:a441:7147:1:70dc:dbc7:fcfe:c605
          240d:1a:124:5300:2cb0:2c4d:b748:3853
          2001:13d8:1c01:2000:2470::1
          2a03:4000:6:416c::43
          2600:1f14:6ae:d900:6550:3fc5:e074:a72c
          2a02:8106:22e:9d50::227
          123.5.48.235
          80.61.148.155
          159.65.33.252
          138.68.93.0
          13.78.125.30
          138.68.174.249
          171.124.53.172
          159.89.25.106
          148.251.83.196
          24.99.150.25
          192.3.11.24
          111.206.188.112
          88.198.39.205
          87.122.81.82
          96.27.129.94
          218.75.140.43
          218.75.158.185
          46.167.117.12
          195.43.141.28
          13.209.0.41
          95.216.26.158

This is confirmed by Bitcoin.org's developer guide which says

When started for the first time, programs don’t know the IP addresses of any active full nodes. In order to discover some IP addresses, they query one or more DNS names (called DNS seeds) hardcoded into Bitcoin Core and BitcoinJ. The response to the lookup should include one or more DNS A records with the IP addresses of full nodes that may accept new incoming connections.

It goes on to describe the protocols that can be used to communicate with these nodes.