DHT InfoHash Lookup sequence. PeerID vs InfoHash

Question

I know there is a previous question about this somewhere on SO, but I cannot find it again. The relationship between NodeId and InfoHash. Is the following diagram roughly correct?

Background (no need to read)

I'm trying to implement my own DHT/bittorrent application in Java. I know that there are already some excellent implementations that I will never better. But this is purely a hedonistic pursuit. What was it Kennedy said? "we choose to do this not because it is easy.."

I have conquered the easy part, which is to write the low level socket handling and Remote Procedure Call syntax etc. Now I am on to the hard part, I must behave responsibly and service incoming requests on the DHT. (maintain KBuckets etc.)

Answer 1

Yes that diagram is correct. Here some python code that implements FIND_VALUE algorithm you describe:

async def _get(self, key):
    """Fetch the value associated with KEY from the network"""
    uid = pack(key)
    queried = set()
    while True:
        # retrieve the k nearest peers and remove already queried peers
        peers = await self.peers((None, None), uid)
        peers = [address for address in peers if address not in queried]
        # no more peer to query, the key is not found in the dht
        if not peers:
            raise KeyError(unpack(uid))
        # query selected peers
        queries = dict()
        for address in peers:
            query = self._protocol.rpc(address, "value", uid)
            queries[address] = query
        responses = await gather(queries, return_exceptions=True)
        for (address, response) in responses.items():
            queried.add(address)
            if isinstance(response, Exception):
                continue
            elif response[0] == b"VALUE":
                value = response[1]
                if hash(value) == unpack(uid):
                    # store it
                    @h.transactional
                    def add(tr, key, value):
                        tr.add("QADOM:MAPPING", key, "value", value)

                    await self._run(add, self._hoply, key, value)
                    # at last!
                    return value
                else:
                    log.warning(
                        "[%r] bad value returned from %r", self._uid, address
                    )
                    await self.blacklist(address)
                    continue
            elif response[0] == b"PEERS":
                await self._welcome_peers(response[1])
            else:
                await self.blacklist(address)
                log.warning(
                    "[%r] unknown response %r from %r",
                    self._uid,
                    response[0],
                    address,

This is extract from qadom project peer.py.