Minimal testnet for sharding

What is wrong?

We need the minimal P2P code to do the following.

• Maintain connections to peers, probably from a hardcoded list or at least a list of bootnodes.
• Gossip protocol to pass around new blocks/collations.
• ???

How can it be fixed

Starting point should probably be

• p2p.lightchain.LightChain
• p2p.peer.LESPeer
• p2p.les

We’ll need to implement Command classes for a minimal subset of commands needed to pass around blocks. Looking at the existing commands we will probably need a set of commands loosely as follows.

• Status - For initial handshake and connecting to useful peers.
• Announce - For letting peers know they have a new block.
• GetXXX and XXX for things like requesting and sending blocks or headers.

Then we’ll need to implement a Protocol class to wrap these commands, similar to LESProtocol.

And then finally, a ShardChain class like LightChain which uses the protocol to join the network, find suitable peers, learn the appropraite chain of blocks that it should sync with and then request the blocks and headers and do whatever is needed with them.

[gsalgado]

I suggested p2p.Server because I envisioned it’d be the main service, responsible for orchestrating all others. It’d accept incoming peer connections but also run the DiscoveryProtocol, tell PeerPool to connect to more nodes when necessary, and pass that pool to other services like LightChain or the new ChainSyncer

[gsalgado]

I think it might make more sense to have a new service (p2p.Server, maybe?) that creates and runs a PeerPool, then calls await asyncio.start_server() to get new incoming connections and pass them on to the PeerPool after the auth and base-protocol handshakes are complete