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Update p2p.md 

some fixes and updating the handshake mechanism.
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kdeme 2019-08-20 17:00:25 +02:00 committed by GitHub
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@ -56,7 +56,7 @@ proc newEthereumNode*(keys: KeyPair,
```nim ```nim
node.addCapability(eth) node.addCapability(eth)
node.addCapability(ssh) node.addCapability(shh)
``` ```
Each supplied protocol identifier is a name of a protocol introduced Each supplied protocol identifier is a name of a protocol introduced
@ -72,7 +72,7 @@ proc connectToNetwork*(node: var EthereumNode,
enableDiscovery = true) enableDiscovery = true)
``` ```
The `EthereumNode` will automatically find and maintan a pool of peers The `EthereumNode` will automatically find and maintain a pool of peers
using the Ethereum node discovery protocol. You can access the pool as using the Ethereum node discovery protocol. You can access the pool as
`node.peers`. `node.peers`.
@ -99,7 +99,7 @@ the definition of a RLPx protocol:
The sub-protocols are defined with the `p2pProtocol` macro. It will accept The sub-protocols are defined with the `p2pProtocol` macro. It will accept
a 3-letter identifier for the protocol and the current protocol version: a 3-letter identifier for the protocol and the current protocol version:
Here is how the [DevP2P wire protocol](https://github.com/ethereum/wiki/wiki/%C3%90%CE%9EVp2p-Wire-Protocol) might look like: Here is how the [DevP2P wire protocol](https://github.com/ethereum/devp2p/blob/master/rlpx.md#p2p-capability) might look like:
``` nim ``` nim
p2pProtocol p2p(version = 0): p2pProtocol p2p(version = 0):
@ -177,12 +177,12 @@ The `nextMsg` helper proc can be used to pause the execution of an async
proc until a particular incoming message from a peer arrives: proc until a particular incoming message from a peer arrives:
``` nim ``` nim
proc handshakeExample(peer: Peer) {.async.} = proc helloExample(peer: Peer) {.async.} =
... ...
# send a hello message # send a hello message
peer.hello(...) peer.hello(...)
# wait for a matching hello response # wait for a matching hello response, might want to add a timeout here
let response = await peer.nextMsg(p2p.hello) let response = await peer.nextMsg(p2p.hello)
echo response.clientId # print the name of the Ethereum client echo response.clientId # print the name of the Ethereum client
# used by the other peer (Geth, Parity, Nimbus, etc) # used by the other peer (Geth, Parity, Nimbus, etc)
@ -205,6 +205,9 @@ place). If there are multiple outstanding calls to `nextMsg`, they will
complete together. Any other messages received in the meantime will still complete together. Any other messages received in the meantime will still
be dispatched to their respective handlers. be dispatched to their respective handlers.
For implementing protocol handshakes with `nextMsg` there are specific helpers
which are explained [below](https://github.com/status-im/nim-eth/blob/master/doc/p2p.md#implementing-handshakes-and-reacting-to-other-events).
#### `requestResponse` pairs #### `requestResponse` pairs
``` nim ``` nim
@ -250,21 +253,35 @@ also include handlers for certain important events such as newly connected
peers or misbehaving or disconnecting peers: peers or misbehaving or disconnecting peers:
``` nim ``` nim
p2pProtocol les(version = 2): p2pProtocol foo(version = fooVersion):
onPeerConnected do (peer: Peer):
asyncCheck peer.status [
"networkId": rlp.encode(1),
"keyGenesisHash": rlp.encode(peer.network.chain.genesisHash)
...
]
let otherPeerStatus = await peer.nextMsg(les.status) onPeerConnected do (peer: Peer):
... let m = await peer.status(fooVersion,
timeout = chronos.milliseconds(5000))
if m.protocolVersion == fooVersion:
debug "Foo peer", peer, fooVersion
else:
raise newException(UselessPeerError, "Incompatible Foo version")
onPeerDisconnected do (peer: Peer, reason: DisconnectionReason): onPeerDisconnected do (peer: Peer, reason: DisconnectionReason):
debug "peer disconnected", peer debug "peer disconnected", peer
handshake:
proc status(peer: Peer,
protocolVersion: uint)
``` ```
For handshake messages, where the same type of message needs to be send to and
received from the peer, a `handshake` helper is introduced, as you can see in
the code example above.
Thanks to the `handshake` helper the `status` message will both be send, and be
awaited for receival from the peer, with the defined timeout. In case no `status`
message is received within the defined timeout, an error will be raised which
will result in a disconnect from the peer.
**Note:** Be aware that if currently one of the subprotocol `onPeerConnected` **Note:** Be aware that if currently one of the subprotocol `onPeerConnected`
calls fails, the client will be disconnected as `UselessPeer` but no calls fails, the client will be disconnected as `UselessPeer` but no
`onPeerDisconnect` calls are run. `onPeerDisconnect` calls are run.