Merge pull request #102 from libp2p/docs/discovery-example

docs(examples): Peer Discovery Mechanisms 1, 2 and 3
libp2p · Jul 9, 2017 · c1a4717 · c1a4717
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diff --git a/examples/discovery-mechanisms/1.js b/examples/discovery-mechanisms/1.js
@@ -0,0 +1,58 @@
+'use strict'
+
+const libp2p = require('libp2p')
+const TCP = require('libp2p-tcp')
+const Multiplex = require('libp2p-multiplex')
+const SECIO = require('libp2p-secio')
+const PeerInfo = require('peer-info')
+const Railing = require('libp2p-railing')
+const waterfall = require('async/waterfall')
+
+// Find this list at: https://github.com/ipfs/js-ipfs/blob/master/src/core/runtime/config-nodejs.json
+const bootstrapers = [
+  '/ip4/104.131.131.82/tcp/4001/ipfs/QmaCpDMGvV2BGHeYERUEnRQAwe3N8SzbUtfsmvsqQLuvuJ',
+  '/ip4/104.236.176.52/tcp/4001/ipfs/QmSoLnSGccFuZQJzRadHn95W2CrSFmZuTdDWP8HXaHca9z',
+  '/ip4/104.236.179.241/tcp/4001/ipfs/QmSoLPppuBtQSGwKDZT2M73ULpjvfd3aZ6ha4oFGL1KrGM',
+  '/ip4/162.243.248.213/tcp/4001/ipfs/QmSoLueR4xBeUbY9WZ9xGUUxunbKWcrNFTDAadQJmocnWm',
+  '/ip4/128.199.219.111/tcp/4001/ipfs/QmSoLSafTMBsPKadTEgaXctDQVcqN88CNLHXMkTNwMKPnu',
+  '/ip4/104.236.76.40/tcp/4001/ipfs/QmSoLV4Bbm51jM9C4gDYZQ9Cy3U6aXMJDAbzgu2fzaDs64',
+  '/ip4/178.62.158.247/tcp/4001/ipfs/QmSoLer265NRgSp2LA3dPaeykiS1J6DifTC88f5uVQKNAd',
+  '/ip4/178.62.61.185/tcp/4001/ipfs/QmSoLMeWqB7YGVLJN3pNLQpmmEk35v6wYtsMGLzSr5QBU3',
+  '/ip4/104.236.151.122/tcp/4001/ipfs/QmSoLju6m7xTh3DuokvT3886QRYqxAzb1kShaanJgW36yx'
+]
+
+class MyBundle extends libp2p {
+  constructor (peerInfo) {
+    const modules = {
+      transport: [new TCP()],
+      connection: {
+        muxer: [Multiplex],
+        crypto: [SECIO]
+      },
+      discovery: [new Railing(bootstrapers)]
+    }
+    super(modules, peerInfo)
+  }
+}
+
+let node
+
+waterfall([
+  (cb) => PeerInfo.create(cb),
+  (peerInfo, cb) => {
+    peerInfo.multiaddrs.add('/ip4/0.0.0.0/tcp/0')
+    node = new MyBundle(peerInfo)
+    node.start(cb)
+  }
+], (err) => {
+  if (err) { throw err }
+
+  node.on('peer:discovery', (peer) => {
+    console.log('Discovered:', peer.id.toB58String())
+    node.dial(peer, () => {})
+  })
+
+  node.on('peer:connect', (peer) => {
+    console.log('Connection established to:', peer.id.toB58String())
+  })
+})
diff --git a/examples/discovery-mechanisms/2.js b/examples/discovery-mechanisms/2.js
@@ -0,0 +1,50 @@
+'use strict'
+
+const libp2p = require('libp2p')
+const TCP = require('libp2p-tcp')
+const Multiplex = require('libp2p-multiplex')
+const SECIO = require('libp2p-secio')
+const PeerInfo = require('peer-info')
+const MulticastDNS = require('libp2p-mdns')
+const waterfall = require('async/waterfall')
+const parallel = require('async/parallel')
+
+class MyBundle extends libp2p {
+  constructor (peerInfo) {
+    const modules = {
+      transport: [new TCP()],
+      connection: {
+        muxer: [Multiplex],
+        crypto: [SECIO]
+      },
+      discovery: [new MulticastDNS(peerInfo, { interval: 1000 })]
+    }
+    super(modules, peerInfo)
+  }
+}
+
+function createNode (callback) {
+  let node
+
+  waterfall([
+    (cb) => PeerInfo.create(cb),
+    (peerInfo, cb) => {
+      peerInfo.multiaddrs.add('/ip4/0.0.0.0/tcp/0')
+      node = new MyBundle(peerInfo)
+      node.start(cb)
+    }
+  ], (err) => callback(err, node))
+}
+
+parallel([
+  (cb) => createNode(cb),
+  (cb) => createNode(cb)
+], (err, nodes) => {
+  if (err) { throw err }
+
+  const node1 = nodes[0]
+  const node2 = nodes[1]
+
+  node1.on('peer:discovery', (peer) => console.log('Discovered:', peer.id.toB58String()))
+  node2.on('peer:discovery', (peer) => console.log('Discovered:', peer.id.toB58String()))
+})
diff --git a/examples/discovery-mechanisms/README.md b/examples/discovery-mechanisms/README.md
@@ -1,2 +1,161 @@
-# WIP - This example is still in the works
-![](http://1.bp.blogspot.com/-tNvSnCW0KlQ/U-KOKGVoJkI/AAAAAAAAA3Q/aiSLMeSJFtw/s1600/WIP-sign.jpg)
+# Peer Discovery Mechanisms
+
+A Peer Discovery module enables libp2p to find peers to connect to. Think of these mechanisms as ways to join the rest of the network, as railing points.
+
+With these system, a libp2p node can both have a set of nodes to always connect on boot (bootstraper nodes), discover nodes through locality (e.g connected in the same LAN) or through serendipity (random walks on a DHT).
+
+These mechanisms save configuration and enable a node to operate without any explicit dials, it will just work.
+
+## 1. Bootstrap list of Peers when booting a node
+
+For this demo, we will connect to IPFS default bootstrapper nodes and so, we will need to support the same set of features those nodes have, that are: TCP, multiplex and SECIO. You can see the complete example at [1.js](./1.js).
+
+First, we create our libp2p bundle.
+
+```JavaScript
+class MyBundle extends libp2p {
+  constructor (peerInfo) {
+    const modules = {
+      transport: [new TCP()],
+      connection: {
+        muxer: [Multiplex],
+        crypto: [SECIO]
+      },
+      discovery: [new Railing(bootstrapers)]
+    }
+    super(modules, peerInfo)
+  }
+}
+```
+
+In this bundle, we use a `bootstrappers` array listing peers to connect _on boot_. Here is the list used by js-ipfs and go-ipfs.
+
+```JavaScript
+const bootstrapers = [
+  '/ip4/104.131.131.82/tcp/4001/ipfs/QmaCpDMGvV2BGHeYERUEnRQAwe3N8SzbUtfsmvsqQLuvuJ',
+  '/ip4/104.236.176.52/tcp/4001/ipfs/QmSoLnSGccFuZQJzRadHn95W2CrSFmZuTdDWP8HXaHca9z',
+  '/ip4/104.236.179.241/tcp/4001/ipfs/QmSoLPppuBtQSGwKDZT2M73ULpjvfd3aZ6ha4oFGL1KrGM',
+  '/ip4/162.243.248.213/tcp/4001/ipfs/QmSoLueR4xBeUbY9WZ9xGUUxunbKWcrNFTDAadQJmocnWm',
+  '/ip4/128.199.219.111/tcp/4001/ipfs/QmSoLSafTMBsPKadTEgaXctDQVcqN88CNLHXMkTNwMKPnu',
+  '/ip4/104.236.76.40/tcp/4001/ipfs/QmSoLV4Bbm51jM9C4gDYZQ9Cy3U6aXMJDAbzgu2fzaDs64',
+  '/ip4/178.62.158.247/tcp/4001/ipfs/QmSoLer265NRgSp2LA3dPaeykiS1J6DifTC88f5uVQKNAd',
+  '/ip4/178.62.61.185/tcp/4001/ipfs/QmSoLMeWqB7YGVLJN3pNLQpmmEk35v6wYtsMGLzSr5QBU3',
+  '/ip4/104.236.151.122/tcp/4001/ipfs/QmSoLju6m7xTh3DuokvT3886QRYqxAzb1kShaanJgW36yx'
+]
+```
+
+Now, once we create and start the node, we can listen for events such as `peer:discovery` and `peer:connect`, these events tell us when we found a peer, independently of the discovery mechanism used and when we actually dialed to that peer.
+
+```
+let node
+
+waterfall([
+  (cb) => PeerInfo.create(cb),
+  (peerInfo, cb) => {
+    peerInfo.multiaddrs.add('/ip4/0.0.0.0/tcp/0')
+    node = new MyBundle(peerInfo)
+    node.start(cb)
+  }
+], (err) => {
+  if (err) { throw err }
+
+  // Emitted when a peer has been found
+  node.on('peer:discovery', (peer) => {
+    console.log('Discovered:', peer.id.toB58String())
+    // Note how we need to dial, even if just to warm up the Connection (by not
+    // picking any protocol) in order to get a full Connection. The Peer Discovery
+    // doesn't make any decisions for you.
+    node.dial(peer, () => {})
+  })
+
+  // Once the dial is complete, this event is emitted.
+  node.on('peer:connect', (peer) => {
+    console.log('Connection established to:', peer.id.toB58String())
+  })
+})
+```
+
+From running [1.js](./1.js), you should see the following:
+
+```bash
+> node 1.js
+Discovered: QmaCpDMGvV2BGHeYERUEnRQAwe3N8SzbUtfsmvsqQLuvuJ
+Discovered: QmSoLnSGccFuZQJzRadHn95W2CrSFmZuTdDWP8HXaHca9z
+Discovered: QmSoLPppuBtQSGwKDZT2M73ULpjvfd3aZ6ha4oFGL1KrGM
+Discovered: QmSoLueR4xBeUbY9WZ9xGUUxunbKWcrNFTDAadQJmocnWm
+Discovered: QmSoLSafTMBsPKadTEgaXctDQVcqN88CNLHXMkTNwMKPnu
+Discovered: QmSoLV4Bbm51jM9C4gDYZQ9Cy3U6aXMJDAbzgu2fzaDs64
+Discovered: QmSoLer265NRgSp2LA3dPaeykiS1J6DifTC88f5uVQKNAd
+Discovered: QmSoLMeWqB7YGVLJN3pNLQpmmEk35v6wYtsMGLzSr5QBU3
+Discovered: QmSoLju6m7xTh3DuokvT3886QRYqxAzb1kShaanJgW36yx
+Connection established to: QmSoLMeWqB7YGVLJN3pNLQpmmEk35v6wYtsMGLzSr5QBU3
+Connection established to: QmSoLer265NRgSp2LA3dPaeykiS1J6DifTC88f5uVQKNAd
+Connection established to: QmSoLV4Bbm51jM9C4gDYZQ9Cy3U6aXMJDAbzgu2fzaDs64
+Connection established to: QmSoLueR4xBeUbY9WZ9xGUUxunbKWcrNFTDAadQJmocnWm
+Connection established to: QmSoLPppuBtQSGwKDZT2M73ULpjvfd3aZ6ha4oFGL1KrGM
+Connection established to: QmSoLju6m7xTh3DuokvT3886QRYqxAzb1kShaanJgW36yx
+Connection established to: QmaCpDMGvV2BGHeYERUEnRQAwe3N8SzbUtfsmvsqQLuvuJ
+Connection established to: QmSoLnSGccFuZQJzRadHn95W2CrSFmZuTdDWP8HXaHca9z
+Connection established to: QmSoLSafTMBsPKadTEgaXctDQVcqN88CNLHXMkTNwMKPnu
+```
+
+## 2. MulticastDNS to find other peers in the network
+
+For this example, we need `libp2p-mdns`, go ahead and `npm install` it. You can find the complete solution at [2.js](./2.js).
+
+Update your libp2p bundle to include MulticastDNS.
+
+```JavaScript
+class MyBundle extends libp2p {
+  constructor (peerInfo) {
+    const modules = {
+      transport: [new TCP()],
+      connection: {
+        muxer: [Multiplex],
+        crypto: [SECIO]
+      },
+      // We set the interval here to 1 second so that is faster to observe. The
+      // default is 10 seconds.
+      discovery: [new MulticastDNS(peerInfo, { interval: 1000 })]
+    }
+    super(modules, peerInfo)
+  }
+}
+```
+
+To observe it working, spawn two nodes.
+
+```JavaScript
+parallel([
+  (cb) => createNode(cb),
+  (cb) => createNode(cb)
+], (err, nodes) => {
+  if (err) { throw err }
+
+  const node1 = nodes[0]
+  const node2 = nodes[1]
+
+  node1.on('peer:discovery', (peer) => console.log('Discovered:', peer.id.toB58String()))
+  node2.on('peer:discovery', (peer) => console.log('Discovered:', peer.id.toB58String()))
+})
+```
+
+If you run this example, you will see a continuous stream of each peer discovering each other.
+
+```bash
+> node 2.js
+Discovered: QmSSbQpuKrxkoXHm1v4Pi35hPN5hUHMZoBoawEs2Nhvi8m
+Discovered: QmRcXXhtG8vTqwVBRonKWtV4ovDoC1Fe56WYtcrw694eiJ
+Discovered: QmSSbQpuKrxkoXHm1v4Pi35hPN5hUHMZoBoawEs2Nhvi8m
+Discovered: QmRcXXhtG8vTqwVBRonKWtV4ovDoC1Fe56WYtcrw694eiJ
+Discovered: QmSSbQpuKrxkoXHm1v4Pi35hPN5hUHMZoBoawEs2Nhvi8m
+Discovered: QmRcXXhtG8vTqwVBRonKWtV4ovDoC1Fe56WYtcrw694eiJ
+```
+
+## 3. Where to find other Peer Discovery Mechanisms
+
+There are plenty more Peer Discovery Mechanisms out there, you can:
+
+- Find one in [libp2p-webrtc-star](https://github.com/libp2p/js-libp2p-webrtc-star). Yes, a transport with discovery capabilities! This happens because WebRTC requires a rendezvous point for peers to exchange [SDP](https://tools.ietf.org/html/rfc4317) offer, which means we have one or more points that can introduce peers to each other. Think of it as MulticastDNS for the Web, as in MulticastDNS only works in LAN.
+- Any DHT will offer you a discovery capability. You can simple _random-walk_ the routing tables to find other peers to connect to.
+- You can create your own Discovery service, a registry, a list, a radio beacon, you name it!