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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
node.addCapability(eth)
node.addCapability(ssh)
node.addCapability(shh)
```
Each supplied protocol identifier is a name of a protocol introduced
@ -72,7 +72,7 @@ proc connectToNetwork*(node: var EthereumNode,
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
`node.peers`.
@ -99,7 +99,7 @@ the definition of a RLPx protocol:
The sub-protocols are defined with the `p2pProtocol` macro. It will accept
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
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:
``` nim
proc handshakeExample(peer: Peer) {.async.} =
proc helloExample(peer: Peer) {.async.} =
...
# send a hello message
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)
echo response.clientId # print the name of the Ethereum client
# 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
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
``` nim
@ -250,21 +253,35 @@ also include handlers for certain important events such as newly connected
peers or misbehaving or disconnecting peers:
``` 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)
...
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):
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`
calls fails, the client will be disconnected as `UselessPeer` but no
`onPeerDisconnect` calls are run.