emit listening and always bind in ready for ease of use

README.md

@@ -144,6 +144,10 @@ A boolean indicating if you are currently epheremal or not
 
 Emitted when the routing table is fully bootstrapped. Emitted as a conveinience.
 
+#### `node.on('listening')`
+
+Emitted when the underlying UDP socket is listening. Emitted as a conveinience.
+
 #### `node.on('persistent')`
 
 Emitted when the node is no longer in ephemeral mode.

index.js

@@ -93,6 +93,7 @@ class DHT extends EventEmitter {
     this._nat = new NatAnalyzer(opts.natSampleSize || 16)
     this._onrow = (row) => row.on('full', (node) => this._onfullrow(node, row))
     this._rotateSecrets = false
+    this._bound = false
     this._secrets = [
       Buffer.alloc(32),
       Buffer.alloc(32)
@@ -105,6 +106,11 @@ class DHT extends EventEmitter {
 
     this.table.on('row', this._onrow)
 
+    this.rpc.socket.on('listening', () => {
+      this._bound = true
+      this.emit('listening')
+    })
+
     if (opts.nodes) {
       for (const node of opts.nodes) this.addNode(node)
     }
@@ -192,6 +198,10 @@ class DHT extends EventEmitter {
       this._resolveSampled = null
     }
 
+    if (!this._bound) {
+      await bind(this.rpc.socket, 0)
+    }
+
     this.emit('ready')
   }
 
@@ -666,3 +676,24 @@ function compare (id, a, b) {
 function randomOffset (n) {
   return n - ((Math.random() * 0.5 * n) | 0)
 }
+
+function bind (socket, port) {
+  return new Promise((resolve, reject) => {
+    socket.bind(port)
+
+    socket.on('error', onerror)
+    socket.on('listening', ondone)
+
+    function onerror (err) {
+      socket.removeListener('error', onerror)
+      socket.removeListener('listening', ondone)
+      reject(err)
+    }
+
+    function ondone () {
+      socket.removeListener('error', onerror)
+      socket.removeListener('listening', ondone)
+      resolve()
+    }
+  })
+}

test.js

@@ -163,6 +163,23 @@ tape('shorthand commit', async function (t) {
   destroy(swarm)
 })
 
+tape('after ready it is always bound', async function (t) {
+  t.plan(2)
+
+  const node = new DHT()
+
+  node.on('listening', function () {
+    t.pass('is listening')
+  })
+
+  await node.ready()
+  const addr = node.address()
+
+  t.ok(typeof addr.port, 'is number')
+
+  node.destroy()
+})
+
 tape('timeouts when commiting', async function (t) {
   const [bootstrap, a, b] = await makeSwarm(3)
   let tries = 0