nim-libp2p/examples/circuitrelay.nim

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2.6 KiB
Nim

## # Circuit Relay example
##
## Circuit Relay can be used when a node cannot reach another node
## directly, but can reach it through a another node (the Relay).
##
## That may happen because of NAT, Firewalls, or incompatible transports.
##
## More informations [here](https://docs.libp2p.io/concepts/circuit-relay/).
import chronos, stew/byteutils
import libp2p,
libp2p/protocols/connectivity/relay/[relay, client]
# Helper to create a circuit relay node
proc createCircuitRelaySwitch(r: Relay): Switch =
SwitchBuilder.new()
.withRng(newRng())
.withAddresses(@[ MultiAddress.init("/ip4/0.0.0.0/tcp/0").tryGet() ])
.withTcpTransport()
.withMplex()
.withNoise()
.withCircuitRelay(r)
.build()
proc main() {.async.} =
# Create a custom protocol
let customProtoCodec = "/test"
var proto = new LPProtocol
proto.codec = customProtoCodec
proto.handler = proc(conn: Connection, proto: string) {.async.} =
var msg = string.fromBytes(await conn.readLp(1024))
echo "1 - Dst Received: ", msg
assert "test1" == msg
await conn.writeLp("test2")
msg = string.fromBytes(await conn.readLp(1024))
echo "2 - Dst Received: ", msg
assert "test3" == msg
await conn.writeLp("test4")
let
relay = Relay.new()
clSrc = RelayClient.new()
clDst = RelayClient.new()
# Create three hosts, enable relay client on two of them.
# The third one can relay connections for other peers.
# RelayClient can use a relay, Relay is a relay.
swRel = createCircuitRelaySwitch(relay)
swSrc = createCircuitRelaySwitch(clSrc)
swDst = createCircuitRelaySwitch(clDst)
swDst.mount(proto)
await swRel.start()
await swSrc.start()
await swDst.start()
let
# Create a relay address to swDst using swRel as the relay
addrs = MultiAddress.init($swRel.peerInfo.addrs[0] & "/p2p/" &
$swRel.peerInfo.peerId & "/p2p-circuit").get()
# Connect Dst to the relay
await swDst.connect(swRel.peerInfo.peerId, swRel.peerInfo.addrs)
# Dst reserve a slot on the relay.
let rsvp = await clDst.reserve(swRel.peerInfo.peerId, swRel.peerInfo.addrs)
# Src dial Dst using the relay
let conn = await swSrc.dial(swDst.peerInfo.peerId, @[ addrs ], customProtoCodec)
await conn.writeLp("test1")
var msg = string.fromBytes(await conn.readLp(1024))
echo "1 - Src Received: ", msg
assert "test2" == msg
await conn.writeLp("test3")
msg = string.fromBytes(await conn.readLp(1024))
echo "2 - Src Received: ", msg
assert "test4" == msg
await relay.stop()
await allFutures(swSrc.stop(), swDst.stop(), swRel.stop())
waitFor(main())