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Update p2p.md 

Add explanation on async proc
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kdeme 2019-08-20 17:33:43 +02:00 committed by GitHub
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@ -177,10 +177,10 @@ 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 helloExample(peer: Peer) {.async.} = proc helloExample(peer: Peer) =
... ...
# send a hello message # send a hello message
peer.hello(...) await peer.hello(...)
# wait for a matching hello response, might want to add a timeout here # 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)
@ -205,6 +205,10 @@ 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.
Please also note that the `p2pProtocol` macro will make this `helloExample` proc
`async`. Practically see it as `proc helloExample(peer: Peer) {.async.}`, and
thus never use `waitFor`, but rather `await` inside this proc.
For implementing protocol handshakes with `nextMsg` there are specific helpers 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). which are explained [below](https://github.com/status-im/nim-eth/blob/master/doc/p2p.md#implementing-handshakes-and-reacting-to-other-events).
@ -254,7 +258,6 @@ peers or misbehaving or disconnecting peers:
``` nim ``` nim
p2pProtocol foo(version = fooVersion): p2pProtocol foo(version = fooVersion):
onPeerConnected do (peer: Peer): onPeerConnected do (peer: Peer):
let m = await peer.status(fooVersion, let m = await peer.status(fooVersion,
timeout = chronos.milliseconds(5000)) timeout = chronos.milliseconds(5000))