How to connect the Blockchain to the Network without IP Address?
The bitcoin client has many means to discover other ip in the bitcoin network, in the case of DNS request, which will return many ip address each times, here are the diferent DNS used as in 2017:


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


You can see all the methods used by the bitcoin client to discover nodes here: https://en.bitcoin.it/wiki/Satoshi_Client_Node_Discovery