Does bitcoind need to be up to date to serve blocks to other servers Using bitcoin-13.2. I have an app that connects through port 8333 and fetches blockchain blocks. Problem is that my app connects and exchanges some info with bitcoin-core but I never receive the requested block from the blockchain. This is an intermittent problem. It appears to happen only when bitcoin-core is not connected to the internet. I m trying to isolate what is causing this behavior.

So, is there anything in bitcoin-core that would prevent an out of sync bitcoin-core from answering a 8333 request?

Thanks
Bitcoin clients are perpetually in a state of "catching up with the network".  There is no definitive point at which they are completely caught up.

If you are requesting a block or transaction that the client has yet to see, it will not be able to respond with that block or transaction.  Make sure that what you are requesting is something that the client has already seen and verified.  If you are sure that the client is aware of the data being requested, then you should continue troubleshooting.