diff --git a/shadowsocks-csharp/Controller/Service/AvailabilityStatistics.cs b/shadowsocks-csharp/Controller/Service/AvailabilityStatistics.cs
index af039b18..86c54214 100644
--- a/shadowsocks-csharp/Controller/Service/AvailabilityStatistics.cs
+++ b/shadowsocks-csharp/Controller/Service/AvailabilityStatistics.cs
@@ -107,67 +107,30 @@ namespace Shadowsocks.Controller
                 var bytes = inbound - lastInbound;
                 _lastInboundCounter[id] = inbound;
                 var inboundSpeed = GetSpeedInKiBPerSecond(bytes, _monitorInterval.TotalSeconds);
-                _inboundSpeedRecords.GetOrAdd(id, new List<int> {inboundSpeed}).Add(inboundSpeed);
+                _inboundSpeedRecords.GetOrAdd(id, (k) =>
+                {
+                    List<int> records = new List<int>();
+                    records.Add(inboundSpeed);
+                    return records;
+                });
 
                 var lastOutbound = _lastOutboundCounter[id];
                 var outbound = _outboundCounter[id];
                 bytes = outbound - lastOutbound;
                 _lastOutboundCounter[id] = outbound;
                 var outboundSpeed = GetSpeedInKiBPerSecond(bytes, _monitorInterval.TotalSeconds);
-                _outboundSpeedRecords.GetOrAdd(id, new List<int> {outboundSpeed}).Add(outboundSpeed);
+                _outboundSpeedRecords.GetOrAdd(id, (k) =>
+                {
+                    List<int> records = new List<int>();
+                    records.Add(outboundSpeed);
+                    return records;
+                });
 
                 Logging.Debug(
                     $"{id}: current/max inbound {inboundSpeed}/{_inboundSpeedRecords[id].Max()} KiB/s, current/max outbound {outboundSpeed}/{_outboundSpeedRecords[id].Max()} KiB/s");
             }
         }
 
-        private async Task<ICMPResult> ICMPTest(Server server)
-        {
-            Logging.Debug("Ping " + server.FriendlyName());
-            if (server.server == "") return null;
-            var result = new ICMPResult(server);
-            try
-            {
-                var IP =
-                    Dns.GetHostAddresses(server.server)
-                        .First(
-                            ip =>
-                                ip.AddressFamily == AddressFamily.InterNetwork ||
-                                ip.AddressFamily == AddressFamily.InterNetworkV6);
-                var ping = new Ping();
-
-                foreach (var _ in Enumerable.Range(0, Repeat))
-                {
-                    try
-                    {
-                        var reply = await ping.SendTaskAsync(IP, TimeoutMilliseconds);
-                        if (reply.Status.Equals(IPStatus.Success))
-                        {
-                            result.RoundtripTime.Add((int?) reply.RoundtripTime);
-                        }
-                        else
-                        {
-                            result.RoundtripTime.Add(null);
-                        }
-
-                        //Do ICMPTest in a random frequency
-                        Thread.Sleep(TimeoutMilliseconds + new Random().Next()%TimeoutMilliseconds);
-                    }
-                    catch (Exception e)
-                    {
-                        Logging.Error($"An exception occured while eveluating {server.FriendlyName()}");
-                        Logging.LogUsefulException(e);
-                    }
-                }
-            }
-            catch (Exception e)
-            {
-                Logging.Error($"An exception occured while eveluating {server.FriendlyName()}");
-                Logging.LogUsefulException(e);
-            }
-            return result;
-        }
-
         private void Reset()
         {
             _inboundSpeedRecords.Clear();
@@ -183,7 +146,7 @@ namespace Shadowsocks.Controller
             FilterRawStatistics();
         }
 
-        private async void UpdateRecords()
+        private void UpdateRecords()
         {
             var records = new Dictionary<string, StatisticsRecord>();
 
@@ -202,14 +165,11 @@ namespace Shadowsocks.Controller
                     records[id] = record;
                 else
                     records.Add(id, record);
-            }
-
-            if (Config.Ping)
-            {
-                var icmpResults = await TaskEx.WhenAll(_controller.GetCurrentConfiguration().configs.Select(ICMPTest));
-                foreach (var result in icmpResults.Where(result => result != null))
+                if (Config.Ping)
                 {
-                    records[result.Server.Identifier()].SetResponse(result.RoundtripTime);
+                    MyPing ping = new MyPing(server, Repeat, record);
+                    ping.Completed += ping_Completed;
+                    ping.Start();
                 }
             }
 
@@ -219,15 +179,22 @@ namespace Shadowsocks.Controller
             }
         }
 
+        private void ping_Completed(object sender, MyPing.CompletedEventArgs e)
+        {
+            Server server = ((MyPing)sender).server;
+            StatisticsRecord record = (StatisticsRecord)((MyPing)sender).userstate;
+            record.SetResponse(e.RoundtripTime);
+        }
+
         private void AppendRecord(string serverIdentifier, StatisticsRecord record)
         {
             List<StatisticsRecord> records;
             if (!RawStatistics.TryGetValue(serverIdentifier, out records))
             {
                 records = new List<StatisticsRecord>();
+                RawStatistics[serverIdentifier] = records;
             }
             records.Add(record);
-            RawStatistics[serverIdentifier] = records;
         }
 
         private void Save()
@@ -298,21 +265,10 @@ namespace Shadowsocks.Controller
 
         private static int GetSpeedInKiBPerSecond(long bytes, double seconds)
         {
-            var result = (int) (bytes/seconds)/1024;
+            var result = (int)(bytes / seconds) / 1024;
             return result;
         }
 
-        private class ICMPResult
-        {
-            internal readonly List<int?> RoundtripTime = new List<int?>();
-            internal readonly Server Server;
-
-            internal ICMPResult(Server server)
-            {
-                Server = server;
-            }
-        }
-
         public void Dispose()
         {
             _recorder.Dispose();
@@ -321,44 +277,131 @@ namespace Shadowsocks.Controller
 
         public void UpdateLatency(Server server, int latency)
         {
-            List<int> records;
-            _latencyRecords.TryGetValue(server.Identifier(), out records);
-            if (records == null)
+            _latencyRecords.GetOrAdd(server.Identifier(), (k) =>
             {
-                records = new List<int>();
-            }
-            records.Add(latency);
-            _latencyRecords[server.Identifier()] = records;
+                List<int> records = new List<int>();
+                records.Add(latency);
+                return records;
+            });
         }
 
         public void UpdateInboundCounter(Server server, long n)
         {
-            long count;
-            if (_inboundCounter.TryGetValue(server.Identifier(), out count))
-            {
-                count += n;
-            }
-            else
+            _inboundCounter.AddOrUpdate(server.Identifier(), (k) =>
             {
-                count = n;
-                _lastInboundCounter[server.Identifier()] = 0;
-            }
-            _inboundCounter[server.Identifier()] = count;
+                _lastInboundCounter.GetOrAdd(server.Identifier(), 0);
+                return n;
+            }, (k, v) => (v + n));
         }
 
         public void UpdateOutboundCounter(Server server, long n)
         {
-            long count;
-            if (_outboundCounter.TryGetValue(server.Identifier(), out count))
+            _outboundCounter.AddOrUpdate(server.Identifier(), (k) =>
+            {
+                _lastOutboundCounter.GetOrAdd(server.Identifier(), 0);
+                return n;
+            }, (k, v) => (v + n));
+        }
+
+        class MyPing
+        {
+            //arguments for ICMP tests
+            public const int TimeoutMilliseconds = 500;
+
+            public EventHandler<CompletedEventArgs> Completed;
+            public Server server;
+            public object userstate;
+
+            private int repeat;
+            private IPAddress ip;
+            private Ping ping;
+            private List<int?> RoundtripTime;
+
+            public MyPing(Server server, int repeat, object userstate)
+            {
+                this.server = server;
+                this.repeat = repeat;
+                this.userstate = userstate;
+                RoundtripTime = new List<int?>(repeat);
+                ping = new Ping();
+                ping.PingCompleted += Ping_PingCompleted;
+            }
+
+            public void Start()
+            {
+                Logging.Debug("Ping " + server.FriendlyName());
+                if (server.server == "")
+                    return;
+                new Task(() => ICMPTest(0)).Start();
+            }
+
+            private void ICMPTest(int delay)
+            {
+                try
+                {
+                    if (ip == null)
+                    {
+                        ip = Dns.GetHostAddresses(server.server)
+                                .First(
+                                    ip =>
+                                        ip.AddressFamily == AddressFamily.InterNetwork ||
+                                        ip.AddressFamily == AddressFamily.InterNetworkV6);
+                    }
+                    repeat--;
+                    if (delay > 0)
+                        Thread.Sleep(delay);
+                    ping.SendAsync(ip, TimeoutMilliseconds, null);
+                }
+                catch (Exception e)
+                {
+                    Logging.Error($"An exception occured while eveluating {server.FriendlyName()}");
+                    Logging.LogUsefulException(e);
+                }
+            }
+
+            private void Ping_PingCompleted(object sender, PingCompletedEventArgs e)
             {
-                count += n;
+                try
+                {
+                    if (e.Reply.Status == IPStatus.Success)
+                    {
+                        RoundtripTime.Add((int?)e.Reply.RoundtripTime);
+                    }
+                    else
+                    {
+                        RoundtripTime.Add(null);
+                    }
+                    TestNext();
+                }
+                catch (Exception ex)
+                {
+                    Logging.Error($"An exception occured while eveluating {server.FriendlyName()}");
+                    Logging.LogUsefulException(ex);
+                }
             }
-            else
+
+            private void TestNext()
             {
-                count = n;
-                _lastOutboundCounter[server.Identifier()] = 0;
+                if (repeat > 0)
+                {
+                    //Do ICMPTest in a random frequency
+                    int delay = TimeoutMilliseconds + new Random().Next() % TimeoutMilliseconds;
+                    new Task(() => ICMPTest(delay)).Start();
+                }
+                else
+                {
+                    Completed?.Invoke(this, new CompletedEventArgs
+                    {
+                        RoundtripTime = RoundtripTime
+                    });
+                }
+            }
+
+            public class CompletedEventArgs : EventArgs
+            {
+                public List<int?> RoundtripTime;
             }
-            _outboundCounter[server.Identifier()] = count;
         }
+
     }
 }
diff --git a/shadowsocks-csharp/Controller/ShadowsocksController.cs b/shadowsocks-csharp/Controller/ShadowsocksController.cs
index 13c6650d..8a66ee63 100755
--- a/shadowsocks-csharp/Controller/ShadowsocksController.cs
+++ b/shadowsocks-csharp/Controller/ShadowsocksController.cs
@@ -5,7 +5,6 @@ using System.Net;
 using System.Net.Sockets;
 using System.Text;
 using System.Threading;
-using System.Threading.Tasks;
 using Newtonsoft.Json;
 
 using Shadowsocks.Controller.Strategy;
@@ -311,7 +310,7 @@ namespace Shadowsocks.Controller
         {
             if (_config.availabilityStatistics)
             {
-                new Task(() => availabilityStatistics.UpdateLatency(server, (int) latency.TotalMilliseconds)).Start();
+                availabilityStatistics.UpdateLatency(server, (int)latency.TotalMilliseconds);
             }
         }
 
@@ -320,7 +319,7 @@ namespace Shadowsocks.Controller
             Interlocked.Add(ref inboundCounter, n);
             if (_config.availabilityStatistics)
             {
-                new Task(() => availabilityStatistics.UpdateInboundCounter(server, n)).Start();
+                availabilityStatistics.UpdateInboundCounter(server, n);
             }
         }
 
@@ -329,7 +328,7 @@ namespace Shadowsocks.Controller
             Interlocked.Add(ref outboundCounter, n);
             if (_config.availabilityStatistics)
             {
-                new Task(() => availabilityStatistics.UpdateOutboundCounter(server, n)).Start();
+                availabilityStatistics.UpdateOutboundCounter(server, n);
             }
         }
 
diff --git a/shadowsocks-csharp/packages.config b/shadowsocks-csharp/packages.config
index 6f3efda8..b80520d3 100644
--- a/shadowsocks-csharp/packages.config
+++ b/shadowsocks-csharp/packages.config
@@ -3,11 +3,6 @@
   <package id="Caseless.Fody" version="1.4.1" targetFramework="net40-client" developmentDependency="true" />
   <package id="Costura.Fody" version="1.3.3.0" targetFramework="net40-client" developmentDependency="true" />
   <package id="Fody" version="1.29.4" targetFramework="net40-client" developmentDependency="true" />
-  <package id="Microsoft.Bcl" version="1.1.10" targetFramework="net40-client" />
-  <package id="Microsoft.Bcl.Async" version="1.0.168" targetFramework="net40-client" />
-  <package id="Microsoft.Bcl.Build" version="1.0.21" targetFramework="net40-client" />
-  <package id="Microsoft.Net.Http" version="2.0.20710.0" targetFramework="net4-client" />
   <package id="Newtonsoft.Json" version="8.0.2" targetFramework="net40-client" />
   <package id="StringEx.CS" version="0.2" targetFramework="net40-client" />
-  <package id="System.Net.Http" version="2.0.20710.0" targetFramework="net40-client" />
 </packages>
\ No newline at end of file
diff --git a/shadowsocks-csharp/shadowsocks-csharp.csproj b/shadowsocks-csharp/shadowsocks-csharp.csproj
index 008134ae..93fdfc73 100644
--- a/shadowsocks-csharp/shadowsocks-csharp.csproj
+++ b/shadowsocks-csharp/shadowsocks-csharp.csproj
@@ -66,18 +66,6 @@
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="Microsoft.CSharp" />
-    <Reference Include="Microsoft.Threading.Tasks, Version=1.0.12.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
-      <HintPath>3rd\Microsoft.Bcl.Async.1.0.168\lib\net40\Microsoft.Threading.Tasks.dll</HintPath>
-      <Private>True</Private>
-    </Reference>
-    <Reference Include="Microsoft.Threading.Tasks.Extensions, Version=1.0.12.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
-      <HintPath>3rd\Microsoft.Bcl.Async.1.0.168\lib\net40\Microsoft.Threading.Tasks.Extensions.dll</HintPath>
-      <Private>True</Private>
-    </Reference>
-    <Reference Include="Microsoft.Threading.Tasks.Extensions.Desktop, Version=1.0.168.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
-      <HintPath>3rd\Microsoft.Bcl.Async.1.0.168\lib\net40\Microsoft.Threading.Tasks.Extensions.Desktop.dll</HintPath>
-      <Private>True</Private>
-    </Reference>
     <Reference Include="Microsoft.VisualBasic" />
     <Reference Include="Newtonsoft.Json, Version=8.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed, processorArchitecture=MSIL">
       <HintPath>3rd\Newtonsoft.Json.8.0.2\lib\net40\Newtonsoft.Json.dll</HintPath>
@@ -88,27 +76,7 @@
     <Reference Include="System" />
     <Reference Include="System.Data" />
     <Reference Include="System.Drawing" />
-    <Reference Include="System.IO, Version=2.6.10.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
-      <HintPath>3rd\Microsoft.Bcl.1.1.10\lib\net40\System.IO.dll</HintPath>
-      <Private>True</Private>
-    </Reference>
     <Reference Include="System.Net" />
-    <Reference Include="System.Net.Http, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
-      <HintPath>3rd\Microsoft.Net.Http.2.0.20710.0\lib\net40\System.Net.Http.dll</HintPath>
-      <Private>True</Private>
-    </Reference>
-    <Reference Include="System.Net.Http.WebRequest, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
-      <HintPath>3rd\Microsoft.Net.Http.2.0.20710.0\lib\net40\System.Net.Http.WebRequest.dll</HintPath>
-      <Private>True</Private>
-    </Reference>
-    <Reference Include="System.Runtime, Version=2.6.10.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
-      <HintPath>3rd\Microsoft.Bcl.1.1.10\lib\net40\System.Runtime.dll</HintPath>
-      <Private>True</Private>
-    </Reference>
-    <Reference Include="System.Threading.Tasks, Version=2.6.10.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
-      <HintPath>3rd\Microsoft.Bcl.1.1.10\lib\net40\System.Threading.Tasks.dll</HintPath>
-      <Private>True</Private>
-    </Reference>
     <Reference Include="System.Windows.Forms" />
     <Reference Include="System.Windows.Forms.DataVisualization" />
     <Reference Include="System.Xaml" />
@@ -330,10 +298,8 @@
     <PropertyGroup>
       <ErrorText>This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them.  For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is {0}.</ErrorText>
     </PropertyGroup>
-    <Error Condition="!Exists('3rd\Microsoft.Bcl.Build.1.0.21\build\Microsoft.Bcl.Build.targets')" Text="$([System.String]::Format('$(ErrorText)', '3rd\Microsoft.Bcl.Build.1.0.21\build\Microsoft.Bcl.Build.targets'))" />
     <Error Condition="!Exists('3rd\Fody.1.29.4\build\portable-net+sl+win+wpa+wp\Fody.targets')" Text="$([System.String]::Format('$(ErrorText)', '3rd\Fody.1.29.4\build\portable-net+sl+win+wpa+wp\Fody.targets'))" />
   </Target>
-  <Import Project="3rd\Microsoft.Bcl.Build.1.0.21\build\Microsoft.Bcl.Build.targets" Condition="Exists('3rd\Microsoft.Bcl.Build.1.0.21\build\Microsoft.Bcl.Build.targets')" />
   <Import Project="3rd\Fody.1.29.4\build\portable-net+sl+win+wpa+wp\Fody.targets" Condition="Exists('3rd\Fody.1.29.4\build\portable-net+sl+win+wpa+wp\Fody.targets')" />
   <UsingTask TaskName="CosturaCleanup" AssemblyFile="$(MSBuildToolsPath)\Microsoft.Build.Tasks.v4.0.dll" TaskFactory="CodeTaskFactory">
     <ParameterGroup>
diff --git a/test/packages.config b/test/packages.config
deleted file mode 100644
index 7d90c6e3..00000000
--- a/test/packages.config
+++ /dev/null
@@ -1,8 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<packages>
-  <package id="Microsoft.Bcl" version="1.1.10" targetFramework="net45" />
-  <package id="Microsoft.Bcl.Async" version="1.0.168" targetFramework="net45" />
-  <package id="Microsoft.Bcl.Build" version="1.0.21" targetFramework="net45" />
-  <package id="Microsoft.Net.Http" version="2.2.29" targetFramework="net45" />
-  <package id="System.Net.Http" version="4.0.0" targetFramework="net45" />
-</packages>
\ No newline at end of file
diff --git a/test/test.csproj b/test/test.csproj
index 777a10b8..d1c3fa2e 100755
--- a/test/test.csproj
+++ b/test/test.csproj
@@ -35,29 +35,9 @@
     <StartupObject />
   </PropertyGroup>
   <ItemGroup>
-    <Reference Include="Microsoft.Threading.Tasks, Version=1.0.12.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
-      <HintPath>..\shadowsocks-csharp\3rd\Microsoft.Bcl.Async.1.0.168\lib\net40\Microsoft.Threading.Tasks.dll</HintPath>
-      <Private>True</Private>
-    </Reference>
-    <Reference Include="Microsoft.Threading.Tasks.Extensions, Version=1.0.12.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
-      <HintPath>..\shadowsocks-csharp\3rd\Microsoft.Bcl.Async.1.0.168\lib\net40\Microsoft.Threading.Tasks.Extensions.dll</HintPath>
-      <Private>True</Private>
-    </Reference>
-    <Reference Include="Microsoft.Threading.Tasks.Extensions.Desktop, Version=1.0.168.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
-      <HintPath>..\shadowsocks-csharp\3rd\Microsoft.Bcl.Async.1.0.168\lib\net40\Microsoft.Threading.Tasks.Extensions.Desktop.dll</HintPath>
-      <Private>True</Private>
-    </Reference>
     <Reference Include="System" />
     <Reference Include="System.Net" />
     <Reference Include="System.Net.Http" />
-    <Reference Include="System.Net.Http.Extensions, Version=2.2.29.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
-      <HintPath>..\shadowsocks-csharp\3rd\Microsoft.Net.Http.2.2.29\lib\net45\System.Net.Http.Extensions.dll</HintPath>
-      <Private>True</Private>
-    </Reference>
-    <Reference Include="System.Net.Http.Primitives, Version=4.2.29.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
-      <HintPath>..\shadowsocks-csharp\3rd\Microsoft.Net.Http.2.2.29\lib\net45\System.Net.Http.Primitives.dll</HintPath>
-      <Private>True</Private>
-    </Reference>
     <Reference Include="System.Net.Http.WebRequest" />
   </ItemGroup>
   <Choose>
@@ -82,9 +62,6 @@
       <Name>shadowsocks-csharp</Name>
     </ProjectReference>
   </ItemGroup>
-  <ItemGroup>
-    <None Include="packages.config" />
-  </ItemGroup>
   <Choose>
     <When Condition="'$(VisualStudioVersion)' == '10.0' And '$(IsCodedUITest)' == 'True'">
       <ItemGroup>
@@ -105,13 +82,6 @@
   </Choose>
   <Import Project="$(VSToolsPath)\TeamTest\Microsoft.TestTools.targets" Condition="Exists('$(VSToolsPath)\TeamTest\Microsoft.TestTools.targets')" />
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
-  <Import Project="..\shadowsocks-csharp\3rd\Microsoft.Bcl.Build.1.0.21\build\Microsoft.Bcl.Build.targets" Condition="Exists('..\shadowsocks-csharp\3rd\Microsoft.Bcl.Build.1.0.21\build\Microsoft.Bcl.Build.targets')" />
-  <Target Name="EnsureNuGetPackageBuildImports" BeforeTargets="PrepareForBuild">
-    <PropertyGroup>
-      <ErrorText>This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them.  For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is {0}.</ErrorText>
-    </PropertyGroup>
-    <Error Condition="!Exists('..\shadowsocks-csharp\3rd\Microsoft.Bcl.Build.1.0.21\build\Microsoft.Bcl.Build.targets')" Text="$([System.String]::Format('$(ErrorText)', '..\shadowsocks-csharp\3rd\Microsoft.Bcl.Build.1.0.21\build\Microsoft.Bcl.Build.targets'))" />
-  </Target>
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.
   <Target Name="BeforeBuild">