Apply this diff to bfc0349506fc8d2ea80e80eb36cbd838092313a6 of zeromq/netmq to make it compatible with .Net 3.5, thanks to https://gist.github.com/tobi-tobsen/6389448 for an earlier version of this patch.

net35.diff

diff --git a/src/NetMQ.Tests/NetMQ.Tests.csproj b/src/NetMQ.Tests/NetMQ.Tests.csproj
index bb7590e..5d4f9f8 100644
--- a/src/NetMQ.Tests/NetMQ.Tests.csproj
+++ b/src/NetMQ.Tests/NetMQ.Tests.csproj
@@ -12,6 +12,8 @@
     <AssemblyName>NetMQ.Tests</AssemblyName>
     <TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
+    <TargetFrameworkProfile>
+    </TargetFrameworkProfile>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <DebugSymbols>true</DebugSymbols>
@@ -64,7 +66,6 @@
     <Compile Include="ExpectedZmqException.cs" />
     <Compile Include="MessageTests.cs" />
     <Compile Include="MonitorPollTests.cs" />
-    <Compile Include="NetMQSchedulerTest.cs" />
     <Compile Include="NetMQTestRunner.cs" />
     <Compile Include="PgmTests.cs" />
     <Compile Include="PollerTests.cs" />
@@ -73,7 +74,6 @@
     <Compile Include="PubSubTests.cs" />
     <Compile Include="PushPullTests.cs" />
     <Compile Include="ReqRepTests.cs" />
-    <Compile Include="Security\SecureChannelTests.cs" />
     <Compile Include="SocketTests.cs" />
     <Compile Include="StreamTests.cs" />
     <Compile Include="zmq\YQueueTests.cs" />
@@ -87,6 +87,7 @@
   </ItemGroup>
   <ItemGroup />
   <ItemGroup>
+    <None Include="app.config" />
     <None Include="NetMQ.Testing.crt">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>
diff --git a/src/NetMQ/Devices/ThreadedDeviceRunner.cs b/src/NetMQ/Devices/ThreadedDeviceRunner.cs
index b6ef2a3..f6e304c 100644
--- a/src/NetMQ/Devices/ThreadedDeviceRunner.cs
+++ b/src/NetMQ/Devices/ThreadedDeviceRunner.cs
@@ -1,4 +1,4 @@
-using System.Threading.Tasks;
+using System.Threading;
 
 namespace NetMQ.Devices
 {
@@ -14,7 +14,7 @@ public ThreadedDeviceRunner(IDevice device)
 
         public override void Start()
         {
-            Task.Factory.StartNew(Device.Run, TaskCreationOptions.LongRunning);
+            ThreadPool.QueueUserWorkItem(delegate { this.Device.Run(); });
         }
     }
 }
\ No newline at end of file
diff --git a/src/NetMQ/Monitoring/NetMQMonitor.cs b/src/NetMQ/Monitoring/NetMQMonitor.cs
index 66c5a61..b649d88 100644
--- a/src/NetMQ/Monitoring/NetMQMonitor.cs
+++ b/src/NetMQ/Monitoring/NetMQMonitor.cs
@@ -13,7 +13,7 @@ public class NetMQMonitor : IDisposable
         private bool m_isOwner;
         private Poller m_attachedPoller = null;
 
-        readonly CancellationTokenSource m_cancellationTokenSource = new CancellationTokenSource();
+        bool m_cancellationTokenSource = false;
 
         private readonly ManualResetEvent m_isStoppedEvent = new ManualResetEvent(true);
 
@@ -214,7 +214,7 @@ public void Start()
 
             try
             {
-                while (!m_cancellationTokenSource.IsCancellationRequested)
+                while (!m_cancellationTokenSource)
                 {
                     MonitoringSocket.Poll(Timeout);
                 }
@@ -233,7 +233,7 @@ public void Stop()
                 throw new InvalidOperationException("Monitor attached to a poller, please detach from poller and don't use the stop method");
             }
 
-            m_cancellationTokenSource.Cancel();
+            m_cancellationTokenSource = true;
             m_isStoppedEvent.WaitOne();
         }
 
diff --git a/src/NetMQ/NetMQ.csproj b/src/NetMQ/NetMQ.csproj
index dcb6b5b..3a1dfa2 100644
--- a/src/NetMQ/NetMQ.csproj
+++ b/src/NetMQ/NetMQ.csproj
@@ -10,8 +10,9 @@
     <AppDesignerFolder>Properties</AppDesignerFolder>
     <RootNamespace>NetMQ</RootNamespace>
     <AssemblyName>NetMQ</AssemblyName>
-    <TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
+    <TargetFrameworkVersion>v3.5</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
+    <TargetFrameworkProfile>Client</TargetFrameworkProfile>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <DebugSymbols>true</DebugSymbols>
@@ -38,7 +39,6 @@
   </ItemGroup>
   <ItemGroup>
     <Compile Include="IReceivingSocket.cs" />
-    <Compile Include="NetMQScheduler.cs" />
     <Compile Include="OutgoingSocketExtensions.cs" />
     <Compile Include="ErrorPollingException.cs" />
     <Compile Include="NetMQFrame.cs" />
@@ -50,25 +50,6 @@
     <Compile Include="NetMQSocketEventArgs.cs" />
     <Compile Include="Poller.cs" />
     <Compile Include="ReceivingSocketExtensions.cs" />
-    <Compile Include="Security\NetMQSecurityException.cs">
-      <SubType>Code</SubType>
-    </Compile>
-    <Compile Include="Security\CipherSuite.cs" />
-    <Compile Include="Security\V0_1\ContentType.cs" />
-    <Compile Include="Security\V0_1\HandshakeLayer.cs" />
-    <Compile Include="Security\V0_1\HandshakeMessages\ClientHelloMessage.cs" />
-    <Compile Include="Security\V0_1\HandshakeMessages\FinishedMessage.cs" />
-    <Compile Include="Security\V0_1\HandshakeMessages\HandshakeMessage.cs" />
-    <Compile Include="Security\V0_1\HandshakeMessages\CertificateMessage.cs" />
-    <Compile Include="Security\V0_1\HandshakeMessages\ServerHelloDoneMessage.cs" />
-    <Compile Include="Security\V0_1\HandshakeMessages\ServerHelloMessage.cs" />
-    <Compile Include="Security\V0_1\HandshakeMessages\ClientKeyExchangeMessage.cs" />
-    <Compile Include="Security\ISecureChannel.cs" />
-    <Compile Include="Security\V0_1\OutgoingMessageBag.cs" />
-    <Compile Include="Security\V0_1\RecordLayer.cs" />
-    <Compile Include="Security\V0_1\SecureChannel.cs" />
-    <Compile Include="Security\V0_1\SecurityParameters.cs" />
-    <Compile Include="Security\V0_1\SHA256PRF.cs" />
     <Compile Include="Sockets\DealerSocket.cs" />
     <Compile Include="Devices\DeviceBase.cs" />
     <Compile Include="Devices\DeviceMode.cs" />
diff --git a/src/NetMQ/NetMQSocket.cs b/src/NetMQ/NetMQSocket.cs
index b4ec985..3eb62fd 100644
--- a/src/NetMQ/NetMQSocket.cs
+++ b/src/NetMQ/NetMQSocket.cs
@@ -169,7 +169,7 @@ public bool Poll(TimeSpan timeout)
 
             ZMQ.Poll(items, (int)timeout.TotalMilliseconds);
 
-            if (item.ResultEvent.HasFlag(PollEvents.PollError) && !IgnoreErrors)
+            if (EnumFlagsHelper.HasFlag(item.ResultEvent, PollEvents.PollError) && !IgnoreErrors)
             {
                 Errors++;
 
@@ -211,7 +211,7 @@ internal void InvokeEvents(object sender, PollEvents events)
             {
                 m_socketEventArgs.Init(events);
 
-                if (events.HasFlag(PollEvents.PollIn))
+                if (EnumFlagsHelper.HasFlag(events, PollEvents.PollIn))
                 {
                     var temp = m_receiveReady;
                     if (temp != null)
@@ -220,7 +220,7 @@ internal void InvokeEvents(object sender, PollEvents events)
                     }
                 }
 
-                if (events.HasFlag(PollEvents.PollOut))
+                if (EnumFlagsHelper.HasFlag(events, PollEvents.PollOut))
                 {
                     var temp = m_sendReady;
                     if (temp != null)
diff --git a/src/NetMQ/NetMQSocketEventArgs.cs b/src/NetMQ/NetMQSocketEventArgs.cs
index 25dd489..0fe77e6 100644
--- a/src/NetMQ/NetMQSocketEventArgs.cs
+++ b/src/NetMQ/NetMQSocketEventArgs.cs
@@ -15,8 +15,8 @@ public NetMQSocketEventArgs(NetMQSocket socket)
 
         internal void Init(PollEvents events)
         {
-            this.ReceiveReady = events.HasFlag(PollEvents.PollIn);
-            this.SendReady = events.HasFlag(PollEvents.PollOut);
+            this.ReceiveReady = EnumFlagsHelper.HasFlag(events, PollEvents.PollIn);
+            this.SendReady = EnumFlagsHelper.HasFlag(events, PollEvents.PollOut);
         }
 
         public NetMQSocket Socket { get; private set; }
diff --git a/src/NetMQ/Poller.cs b/src/NetMQ/Poller.cs
index 218bccd..74a7540 100644
--- a/src/NetMQ/Poller.cs
+++ b/src/NetMQ/Poller.cs
@@ -36,7 +36,7 @@ public NetMQSocket NetMQSocket
         readonly List<NetMQTimer> m_timers = new List<NetMQTimer>();
         readonly List<NetMQTimer> m_zombies = new List<NetMQTimer>();
 
-        readonly CancellationTokenSource m_cancellationTokenSource;
+        bool m_cancellationTokenSource = false;
         readonly ManualResetEvent m_isStoppedEvent = new ManualResetEvent(false);
         private bool m_isStarted;
 
@@ -46,8 +46,6 @@ public NetMQSocket NetMQSocket
         public Poller()
         {
             PollTimeout = 1000;
-
-            m_cancellationTokenSource = new CancellationTokenSource();
         }
 
         public Poller(params NetMQSocket[] sockets)
@@ -274,7 +272,7 @@ public void Start()
                     }
                 }
 
-                while (!m_cancellationTokenSource.IsCancellationRequested)
+                while (!m_cancellationTokenSource)
                 {
                     if (m_isDirty)
                     {
@@ -306,7 +304,7 @@ public void Start()
                         NetMQSocket socket = m_pollact[itemNbr];
                         PollItem item = m_pollset[itemNbr];
 
-                        if (item.ResultEvent.HasFlag(PollEvents.PollError) && !socket.IgnoreErrors)
+                        if (EnumFlagsHelper.HasFlag(item.ResultEvent, PollEvents.PollError) && !socket.IgnoreErrors)
                         {
                             socket.Errors++;
 
@@ -359,7 +357,7 @@ public void Stop(bool waitForCloseToComplete)
 
             if (m_isStarted)
             {
-                m_cancellationTokenSource.Cancel();
+                m_cancellationTokenSource = true;
 
                 if (waitForCloseToComplete)
                 {
diff --git a/src/NetMQ/ReceivingSocketExtensions.cs b/src/NetMQ/ReceivingSocketExtensions.cs
index 1bece12..4c25083 100644
--- a/src/NetMQ/ReceivingSocketExtensions.cs
+++ b/src/NetMQ/ReceivingSocketExtensions.cs
@@ -10,7 +10,7 @@ public static class ReceivingSocketExtensions
     {
         public static byte[] Receive(this IReceivingSocket socket, SendReceiveOptions options, out bool hasMore)
         {
-            return socket.Receive(options.HasFlag(SendReceiveOptions.DontWait), out hasMore);
+            return socket.Receive(EnumFlagsHelper.HasFlag(options, SendReceiveOptions.DontWait), out hasMore);
         }
 
         public static byte[] Receive(this IReceivingSocket socket, out bool hasMore)
@@ -38,7 +38,7 @@ public static string ReceiveString(this IReceivingSocket socket, bool dontWait,
 
         public static string ReceiveString(this IReceivingSocket socket, SendReceiveOptions options, out bool hasMore)
         {
-            return socket.ReceiveString(options.HasFlag(SendReceiveOptions.DontWait), out hasMore);
+            return socket.ReceiveString(EnumFlagsHelper.HasFlag(options, SendReceiveOptions.DontWait), out hasMore);
         }
 
         public static string ReceiveString(this IReceivingSocket socket, SendReceiveOptions options)
@@ -71,10 +71,10 @@ public static NetMQMessage ReceiveMessage(this NetMQSocket socket, TimeSpan time
             var items = new[] { item };
             ZMQ.Poll(items, (int)timeout.TotalMilliseconds);
 
-            if (item.ResultEvent.HasFlag(PollEvents.PollError) && !socket.IgnoreErrors)
+            if (EnumFlagsHelper.HasFlag(item.ResultEvent, PollEvents.PollError) && !socket.IgnoreErrors)
                 throw new ErrorPollingException("Error while polling", socket);
 
-            if (!item.ResultEvent.HasFlag(PollEvents.PollIn))
+            if (!EnumFlagsHelper.HasFlag(item.ResultEvent, PollEvents.PollIn))
                 return null;
 
             var msg = socket.ReceiveMessage();
diff --git a/src/NetMQ/zmq/Address.cs b/src/NetMQ/zmq/Address.cs
index ca40994..20cb869 100644
--- a/src/NetMQ/zmq/Address.cs
+++ b/src/NetMQ/zmq/Address.cs
@@ -50,12 +50,7 @@ public Address(EndPoint endpoint)
         {
             Protocol = TcpProtocol;
 
-            if (endpoint is DnsEndPoint)
-            {
-                DnsEndPoint dnsEndpoint = endpoint as DnsEndPoint;
-                AddressString = dnsEndpoint.Host + ":" + dnsEndpoint.Port;
-            }
-            else if (endpoint is IPEndPoint)
+            if (endpoint is IPEndPoint)
             {
                 IPEndPoint ipEndpoint = endpoint as IPEndPoint;
                 AddressString = ipEndpoint.Address + ":" + ipEndpoint.Port;
diff --git a/src/NetMQ/zmq/Enums.cs b/src/NetMQ/zmq/Enums.cs
index 7724a53..c03e540 100644
--- a/src/NetMQ/zmq/Enums.cs
+++ b/src/NetMQ/zmq/Enums.cs
@@ -122,4 +122,17 @@ public enum PollEvents
         PollOut = 0x2,
         PollError = 0x4
     }
-}
\ No newline at end of file
+
+    public class EnumFlagsHelper
+    {
+        public static bool HasFlag(PollEvents flags, PollEvents flag)
+        {
+            return (flags & flag) != 0;
+        }
+
+        public static bool HasFlag(SendReceiveOptions flags, SendReceiveOptions flag)
+        {
+            return (flags & flag) != 0;
+        }
+    }
+}
diff --git a/src/NetMQ/zmq/RawEncoder.cs b/src/NetMQ/zmq/RawEncoder.cs
index 19ce0b9..e98106e 100644
--- a/src/NetMQ/zmq/RawEncoder.cs
+++ b/src/NetMQ/zmq/RawEncoder.cs
@@ -46,7 +46,7 @@ bool RawMessageSizeReady()
         {
             //  Write message body into the buffer.
             NextStep(m_inProgress.Data, m_inProgress.Size,
-                RawMessageReadyState, !m_inProgress.Flags.HasFlag(MsgFlags.More));
+                RawMessageReadyState, (m_inProgress.Flags & MsgFlags.More) == 0);
             return true;
         }
 
diff --git a/src/NetMQ/zmq/Signaler.cs b/src/NetMQ/zmq/Signaler.cs
index 8ead080..dd6d5bf 100644
--- a/src/NetMQ/zmq/Signaler.cs
+++ b/src/NetMQ/zmq/Signaler.cs
@@ -109,7 +109,7 @@ private void MakeFDpair()
             sync.ReleaseMutex();
 
             // Release the kernel object
-            sync.Dispose();
+            sync.Close();
         }
 
         public Socket FD
diff --git a/src/Samples/Load Balancing Pattern/ROUTERbrokerDEALERworkers/ROUTERbrokerDEALERworkers.csproj b/src/Samples/Load Balancing Pattern/ROUTERbrokerDEALERworkers/ROUTERbrokerDEALERworkers.csproj
index 899734b..eb6f07a 100644
--- a/src/Samples/Load Balancing Pattern/ROUTERbrokerDEALERworkers/ROUTERbrokerDEALERworkers.csproj	
+++ b/src/Samples/Load Balancing Pattern/ROUTERbrokerDEALERworkers/ROUTERbrokerDEALERworkers.csproj	
@@ -48,7 +48,7 @@
     <None Include="App.config" />
   </ItemGroup>
   <ItemGroup>
-    <ProjectReference Include="..\..\..\..\..\..\GitHub\netmq\src\NetMQ\NetMQ.csproj">
+    <ProjectReference Include="..\..\..\NetMQ\NetMQ.csproj">
       <Project>{82934bac-07fb-41ac-ae59-46fee6026a40}</Project>
       <Name>NetMQ</Name>
     </ProjectReference>
diff --git a/src/Samples/Load Balancing Pattern/ROUTERbrokerREQworkers/ROUTERbrokerREQworkers.csproj b/src/Samples/Load Balancing Pattern/ROUTERbrokerREQworkers/ROUTERbrokerREQworkers.csproj
index 9e0529a..eba605d 100644
--- a/src/Samples/Load Balancing Pattern/ROUTERbrokerREQworkers/ROUTERbrokerREQworkers.csproj	
+++ b/src/Samples/Load Balancing Pattern/ROUTERbrokerREQworkers/ROUTERbrokerREQworkers.csproj	
@@ -48,7 +48,7 @@
     <None Include="App.config" />
   </ItemGroup>
   <ItemGroup>
-    <ProjectReference Include="..\..\..\..\..\..\GitHub\netmq\src\NetMQ\NetMQ.csproj">
+    <ProjectReference Include="..\..\..\NetMQ\NetMQ.csproj">
       <Project>{82934bac-07fb-41ac-ae59-46fee6026a40}</Project>
       <Name>NetMQ</Name>
     </ProjectReference>