Also removed CrossChainDigibyteACCTv1Resource, since this is unused, and it seems excessive to maintain support of this for every coin (and potentially every ACCT version).
Direct connections for arbitrary data are currently unlikely to succeed, because those allowing incoming connections generally have their slots maxed out and have reached maxPeers. The idea here is that some connections remain reserved for dedicated arbitrary data transfers, therefore temporarily circumventing the limit (up to a defined maximum number of reserved connections).
Arbitrary data connections will auto disconnect after 2 minutes (we might be able to reduce this at a later date), and it also probably makes sense for the requesting node to disconnect as soon as it has all the chunks that it needs (this part isn't implemented yet).
One downside of this feature is that the listen socket is now going to be accepting connections most of the time, since it is unlikely that we will regularly have 4 data peers connected. This could be improved by modifying the OP_ACCEPT behaviour based on whether we are expecting any data peers to connect. In most cases, this would allow it to remain closed. But for the sake of simplicity I will leave that optimization for a future commit.
This is used to force a quick disconnect for peers that are only connecting for the purposes of requesting data for a specific arbitrary transaction signature.
BlockMessage was broken because the repository 'connection' associated with the message's Block object was closed between message queuing and message sending.
The fix was to serialize Message subclasses on construction, thus freeing reliance on objects passed into constructor.
The serialized byte[] is held by the message between queuing and sending.
This forces messages into one of two 'modes': outgoing or incoming.
Outgoing messages contain serialized byte[] whereas incoming messages unpack a ByteBuffer into Message subclass fields.
As a result, all network message types have been refactored in this way.
More details in Message's class comment.
A knock-on effect is that incoming messages cannot then be sent out - a new message needs to be constructed.
Some changes needed to Arbitrary controller package classes in this respect.
Bonus: Network no longer needs broadcast threads because 'broadcasting' is now simply the act of queuing a message for many peers.
Instead of synchronizing/blocking in Peer.sendMessage(),
we queue messages in a concurrent blocking TransferQueue, with timeout.
In EPC, ChannelWriteTasks consume from TransferQueue, unblocking callers to Peer.sendMessage().
If a new message is to be sent, or socket output buffer is full,
then OP_WRITE is used to wait for socket to become writable again.
Only one ChannelWriteTask per peer can be active/pending at a time.
Each ChannelWriteTask tries to send as much as it can in one go.
Other minor tidy-ups.
As per work done by szisti in PR#45:
Extracted network 'Tasks' to their own classes.
Network.NetworkProcessor reduced to only producing Tasks.
Improved usage of SocketChannel interest-ops.
Eventually this might lead to reducing task-producing synchronization lock into more granular locks.
Work still needed to convert sending messages to a queue and to make use of OP_WRITE instead of sleeping to wait for socket buffer to empty.
Disabled PeerConnectTask producer from checking against connected peers via DNS as it's too slow.
Swapped Peer's replyQueues from SynchronizedMap(wrapped HashMap) to ConcurrentHashMap.
Other minor changes within networking.
