diff --git a/Giselle.Net.EtherNetIP.Test/ImplicitMessaging.cs b/Giselle.Net.EtherNetIP.Test/ImplicitMessaging.cs
index 2216056..9af24b9 100644
--- a/Giselle.Net.EtherNetIP.Test/ImplicitMessaging.cs
+++ b/Giselle.Net.EtherNetIP.Test/ImplicitMessaging.cs
@@ -90,7 +90,7 @@ public static void Identify(ENIPSimpleClient client)
         public static ForwardOpenResult ForwardOpen(ENIPSimpleClient client)
         {
             var openOptions = new ForwardOpenOptions();
-            openOptions.T_O_UDPPort = 2222; // Support alternate sending port
+            openOptions.T_O_UDPPort = 2222; // Support alternate port, Default is 2222
 
             // T : Target
             // O : Originator
diff --git a/Giselle.Net.EtherNetIP/CIP/CIPCodec.cs b/Giselle.Net.EtherNetIP/CIP/CIPCodec.cs
index 2a09320..35db6b9 100644
--- a/Giselle.Net.EtherNetIP/CIP/CIPCodec.cs
+++ b/Giselle.Net.EtherNetIP/CIP/CIPCodec.cs
@@ -3,6 +3,7 @@
 using System.IO;
 using System.Linq;
 using System.Net;
+using System.Net.Sockets;
 using System.Text;
 using System.Threading.Tasks;
 
@@ -65,8 +66,9 @@ public IEnumerable<CommandItem> CreateForwardOpen(ForwardOpenOptions options)
             reqProcessor.WriteByte(options.TickTime);
             reqProcessor.WriteByte(options.TimeoutTicks);
 
-            var otConnectionIDReq = options.O_T_Assembly.ConnectionID != 0 ? options.O_T_Assembly.ConnectionID : (ushort)(this.NextConnectionID() + 0);
-            var toConnectionIDReq = options.T_O_Assembly.ConnectionID != 0 ? options.T_O_Assembly.ConnectionID : (ushort)(this.NextConnectionID() + 1);
+            var connectionID = this.NextConnectionID();
+            var otConnectionIDReq = options.O_T_Assembly.ConnectionID != 0 ? options.O_T_Assembly.ConnectionID : (ushort)(connectionID + 0);
+            var toConnectionIDReq = options.T_O_Assembly.ConnectionID != 0 ? options.T_O_Assembly.ConnectionID : (ushort)(connectionID + 1);
             reqProcessor.WriteUInt(otConnectionIDReq);
             reqProcessor.WriteUInt(toConnectionIDReq);
 
@@ -108,21 +110,20 @@ public IEnumerable<CommandItem> CreateForwardOpen(ForwardOpenOptions options)
             connectionPath.Write(reqProcessor);
             yield return udRequest;
 
-            var requestIPV4EndPoint = new CommandItemEndPoint_T_O
+            var toEndPoint = new CommandItemEndPoint_T_O
             {
                 EndPoint = new IPv4EndPoint() { Family = 2, Port = options.T_O_UDPPort }
             };
 
             if (options.T_O_Assembly.ConnectionType == ConnectionType.Multicast)
             {
-                requestIPV4EndPoint.EndPoint.Address = ((int)GetMulticastAddress((uint)options.LocalAddress.ToIPv4Address())).ToIPv4Address(true);
+                toEndPoint.EndPoint.Address = ((int)GetMulticastAddress((uint)options.LocalAddress.ToIPv4Address())).ToIPv4Address(true);
             }
             else
             {
-                requestIPV4EndPoint.EndPoint.Address = IPAddress.Any;
+                toEndPoint.EndPoint.Address = IPAddress.Any;
             }
-
-            yield return requestIPV4EndPoint;
+            yield return toEndPoint;
         }
 
         public ForwardOpenResult HandleForwardOpen(CommandItems response, ForwardOpenOptions options)
diff --git a/Giselle.Net.EtherNetIP/CIP/ForwardOpenOptions.cs b/Giselle.Net.EtherNetIP/CIP/ForwardOpenOptions.cs
index 7246b47..92fe884 100644
--- a/Giselle.Net.EtherNetIP/CIP/ForwardOpenOptions.cs
+++ b/Giselle.Net.EtherNetIP/CIP/ForwardOpenOptions.cs
@@ -16,6 +16,16 @@ public class ForwardOpenOptions : AbstractOptions
         /// </summary>
         public AssemblyObject T_O_Assembly { get; private set; }
 
+        /// <summary>
+        /// Originator -> Target, Output
+        /// Originator Side Port For Exchange Message
+        /// </summary>
+        public ushort O_T_UDPPort { get; set; }
+        /// <summary>
+        /// Target -> Originator, Input
+        /// Target Side Port For Exchange Message
+        /// Not Supported Yet, Fix Default Value (2222)
+        /// </summary>
         public ushort T_O_UDPPort { get; set; }
         public IPAddress LocalAddress { get; set; }
 
@@ -24,6 +34,7 @@ public ForwardOpenOptions()
             this.O_T_Assembly = new AssemblyObject();
             this.T_O_Assembly = new AssemblyObject();
 
+            this.O_T_UDPPort = 2222;
             this.T_O_UDPPort = 2222;
             this.LocalAddress = IPAddress.Loopback;
         }
@@ -34,6 +45,7 @@ public ForwardOpenOptions(ForwardOpenOptions other)
             this.O_T_Assembly = new AssemblyObject(other.O_T_Assembly);
             this.T_O_Assembly = new AssemblyObject(other.T_O_Assembly);
 
+            this.O_T_UDPPort = other.O_T_UDPPort;
             this.T_O_UDPPort = other.T_O_UDPPort;
             this.LocalAddress = other.LocalAddress;
         }
diff --git a/Giselle.Net.EtherNetIP/ENIP/ENIPSimpleClient.cs b/Giselle.Net.EtherNetIP/ENIP/ENIPSimpleClient.cs
index d4f377d..0db92d3 100644
--- a/Giselle.Net.EtherNetIP/ENIP/ENIPSimpleClient.cs
+++ b/Giselle.Net.EtherNetIP/ENIP/ENIPSimpleClient.cs
@@ -164,11 +164,14 @@ public ForwardOpenResult ForwardOpen(ForwardOpenOptions options)
 
         private UdpClient CreateImplictMessagingClient(ForwardOpenResult openResult)
         {
+            var udpClient = new UdpClient();
             var options = openResult.Options;
-            var port = 2222; // Receiving port is fixed 2222, in my test
+            udpClient.Client.Bind(new IPEndPoint(options.LocalAddress, openResult.Options.T_O_UDPPort));
 
-            var udpClient = new UdpClient();
-            udpClient.Client.Bind(new IPEndPoint(options.LocalAddress, port));
+            if (openResult.Options.O_T_Assembly.ConnectionType == ConnectionType.Multicast)
+            {
+                udpClient.JoinMulticastGroup(openResult.O_T_Address.Address, options.LocalAddress);
+            }
 
             if (openResult.Options.T_O_Assembly.ConnectionType == ConnectionType.Multicast)
             {
@@ -218,7 +221,7 @@ private void RunImplicitSend()
             var udpClient = this.UdpClient;
             var result = this.LastForwardOpenResult;
             var options = result.Options;
-            var targetEndPoint = new IPEndPoint(((IPEndPoint)this.TcpClient.Client.RemoteEndPoint).Address, options.T_O_UDPPort);
+            var targetEndPoint = new IPEndPoint(((IPEndPoint)this.TcpClient.Client.RemoteEndPoint).Address, options.O_T_UDPPort);
 
             try
             {