diff --git a/src/modbus-tcp-server-client.js b/src/modbus-tcp-server-client.js
index dc4a0c5..816a531 100644
--- a/src/modbus-tcp-server-client.js
+++ b/src/modbus-tcp-server-client.js
@@ -64,7 +64,7 @@ module.exports = stampit()
 
     this.onSocketError = function (e) {
       this.logError('Socker error', e)
-    }
+    }.bind(this)
 
     init()
   })
diff --git a/test/heap-test-coils.js b/test/heap-test-coils.js
index 0b1f5cb..490b97e 100644
--- a/test/heap-test-coils.js
+++ b/test/heap-test-coils.js
@@ -2,6 +2,7 @@
 
 const modbus = require('../')
 const v8 = require('v8')
+const Promise = require('bluebird')
 
 const client = modbus.client.tcp.complete({
   'host': 'localhost',
@@ -11,9 +12,21 @@ const client = modbus.client.tcp.complete({
 client.connect()
 
 client.on('connect', function () {
-  for (var i = 1; i < 1e5; i++) {
-    client.readCoils(0, 13)
+
+  let p = Promise.resolve() 
+
+  for (let i = 1; i < 1e5; i++) {
+    p = p.then(client.readCoils(0, 13))
   }
 
-  console.log('Heap:', Math.floor(v8.getHeapStatistics().used_heap_size / 1e6), 'MB')
+  p.then(function () {
+
+    let usedHeapSize = Math.floor(v8.getHeapStatistics().used_heap_size / 1e6);
+
+    console.log('Heap:', usedHeapSize, 'MB')
+ 
+    client.close()
+
+  })
+
 })