feat(lnd): use free port for lnd

Select free ports for lnd from a pool of options. By default we will
use the standard lnd ports (10009 and 9735) but if those are not
available then we will search for free ports in a nearby range.

This allows us to have multiple instances of the wallet running and
avoids possible conflicts with other instances of lnd that the user
may be running.

app/lib/lnd/neutrino.js

@@ -3,6 +3,7 @@
 import split2 from 'split2'
 import { spawn } from 'child_process'
 import EventEmitter from 'events'
+import getPort from 'get-port'
 import { mainLog, lndLog, lndLogGetLevel } from '../utils/log'
 import { fetchBlockHeight } from './util'
 import LndConfig from './config'
@@ -63,9 +64,11 @@ class Neutrino extends EventEmitter {
    * Start the Lnd process in Neutrino mode.
    * @return {Number} PID of the Lnd process that was started.
    */
-  start() {
+  async start() {
     if (this.process) {
-      throw new Error('Neutrino process with PID ${this.process.pid} already exists.')
+      return Promise.reject(
+        new Error('Neutrino process with PID ${this.process.pid} already exists.')
+      )
     }
 
     mainLog.info('Starting lnd in neutrino mode')
@@ -75,13 +78,30 @@ class Neutrino extends EventEmitter {
     mainLog.info(' > cert:', this.lndConfig.cert)
     mainLog.info(' > macaroon:', this.lndConfig.macaroon)
 
+    // Get a free port to use as the rpc listen address.
+    const rpcListen = await getPort({
+      host: 'localhost',
+      port: [10009, 10008, 10007, 10006, 10005, 10004, 10003, 10002, 10001]
+    })
+    this.lndConfig.host = `localhost:${rpcListen}`
+
+    // Get a free port to use as the p2p listen address.
+    const p2pListen = await getPort({
+      host: '0.0.0.0',
+      port: [9735, 9734, 9733, 9732, 9731, 9736, 9737, 9738, 9739]
+    })
+
+    //Configure lnd.
     const neutrinoArgs = [
       `--configfile=${this.lndConfig.configPath}`,
       `--lnddir=${this.lndConfig.lndDir}`,
+      `--listen=0.0.0.0:${p2pListen}`,
+      `--rpclisten=localhost:${rpcListen}`,
       `${this.lndConfig.autopilot ? '--autopilot.active' : ''}`,
       `${this.lndConfig.alias ? `--alias=${this.lndConfig.alias}` : ''}`
     ]
 
+    // Configure neutrino backend.
     if (this.lndConfig.network === 'mainnet') {
       neutrinoArgs.push('--neutrino.connect=mainnet1-btcd.zaphq.io')
       // neutrinoArgs.push('--neutrino.connect=mainnet2-btcd.zaphq.io')
@@ -90,12 +110,14 @@ class Neutrino extends EventEmitter {
       // neutrinoArgs.push('--neutrino.connect=testnet2-btcd.zaphq.io')
     }
 
+    // Log the final config.
     mainLog.info(
       'Spawning Neutrino process: %s %s',
       this.lndConfig.binaryPath,
-      neutrinoArgs.join(' ')
+      neutrinoArgs.filter(v => v != '').join(' ')
     )
 
+    // Spawn lnd process.
     this.process = spawn(this.lndConfig.binaryPath, neutrinoArgs)
       .on('error', error => {
         mainLog.debug('Neutrino process received "error" event with error: %s', error)

app/lib/zap/controller.js

@@ -353,7 +353,7 @@ class ZapController {
       this.sendMessage('lndCfilterHeight', Number(height))
     })
 
-    this.neutrino.start()
+    return this.neutrino.start()
   }
 
   /**

package.json

@@ -292,6 +292,7 @@
     "electron-is-dev": "^0.3.0",
     "electron-store": "^2.0.0",
     "font-awesome": "^4.7.0",
+    "get-port": "^4.0.0",
     "history": "^4.7.2",
     "javascript-state-machine": "^3.1.0",
     "jstimezonedetect": "^1.0.6",

test/unit/lnd/neutrino.spec.js

@@ -179,9 +179,9 @@ describe('Neutrino', function() {
 
   describe('.start', () => {
     describe('called when neutrino is not running', () => {
-      beforeEach(() => {
+      beforeEach(async () => {
         this.neutrino = new Neutrino(new LndConfig())
-        this.neutrino.start()
+        await this.neutrino.start()
       })
       it('should set the subprocess object on the `process` property', () => {
         expect(this.neutrino.process.pid).toBeDefined()
@@ -193,10 +193,10 @@ describe('Neutrino', function() {
         this.neutrino = new Neutrino(new LndConfig())
         this.neutrino.process = mockSpawn()
       })
-      it('should throw an error', () => {
-        expect(() => {
-          this.neutrino.start()
-        }).toThrow()
+      it('should throw an error', async () => {
+        await expect(this.neutrino.start()).rejects.toThrowErrorMatchingInlineSnapshot(
+          `"Neutrino process with PID \${this.process.pid} already exists."`
+        )
       })
     })
   })

yarn.lock

@@ -5571,6 +5571,10 @@ get-port@^3.2.0:
   version "3.2.0"
   resolved "https://registry.yarnpkg.com/get-port/-/get-port-3.2.0.tgz#dd7ce7de187c06c8bf353796ac71e099f0980ebc"
 
+get-port@^4.0.0:
+  version "4.0.0"
+  resolved "https://registry.yarnpkg.com/get-port/-/get-port-4.0.0.tgz#373c85960138ee20027c070e3cb08019fea29816"
+
 [email protected]:
   version "5.0.1"
   resolved "https://registry.yarnpkg.com/get-stdin/-/get-stdin-5.0.1.tgz#122e161591e21ff4c52530305693f20e6393a398"