diff --git a/Modbus.Net/Modbus.Net.Siemens/SiemensPpiProtocol.cs b/Modbus.Net/Modbus.Net.Siemens/SiemensPpiProtocol.cs
index 307ac8e..b25bb07 100644
--- a/Modbus.Net/Modbus.Net.Siemens/SiemensPpiProtocol.cs
+++ b/Modbus.Net/Modbus.Net.Siemens/SiemensPpiProtocol.cs
@@ -18,7 +18,6 @@ namespace Modbus.Net.Siemens
         public SiemensPpiProtocol(byte slaveAddress, byte masterAddress)
             : this(ConfigurationManager.AppSettings["COM"], slaveAddress, masterAddress)
         {
-            ProtocolLinker = new SiemensPpiProtocolLinker(_com, SlaveAddress);
         }
 
         /// <summary>
@@ -31,6 +30,7 @@ namespace Modbus.Net.Siemens
             : base(slaveAddress, masterAddress)
         {
             _com = com;
+            ProtocolLinker = new SiemensPpiProtocolLinker(_com, SlaveAddress);
         }
 
         /// <summary>
@@ -79,10 +79,14 @@ namespace Modbus.Net.Siemens
                 (await (await
                     ForceSendReceiveAsync(this[typeof(ComCreateReferenceSiemensProtocol)],
                             inputStruct)).
-                        SendReceiveAsync(this[typeof(ComConfirmMessageSiemensProtocol)], answer =>
-                        
-                            new ComConfirmMessageSiemensInputStruct(SlaveAddress, MasterAddress)
-                        )).Unwrap<ComConfirmMessageSiemensOutputStruct>();
+                        SendReceiveAsync(this[typeof(ComConfirmMessageSiemensProtocol)], answer => 
+                        answer != null
+                        ? new ComConfirmMessageSiemensInputStruct(SlaveAddress, MasterAddress)
+                        : null)).Unwrap<ComConfirmMessageSiemensOutputStruct>();
+            if (outputStruct == null && ProtocolLinker.IsConnected)
+            {
+                ProtocolLinker.Disconnect();
+            }
             return outputStruct != null;
         }
     }
diff --git a/Modbus.Net/Modbus.Net.Siemens/SiemensPpiProtocolLinker.cs b/Modbus.Net/Modbus.Net.Siemens/SiemensPpiProtocolLinker.cs
index 1146d23..f9db58a 100644
--- a/Modbus.Net/Modbus.Net.Siemens/SiemensPpiProtocolLinker.cs
+++ b/Modbus.Net/Modbus.Net.Siemens/SiemensPpiProtocolLinker.cs
@@ -18,7 +18,7 @@ namespace Modbus.Net.Siemens
         public SiemensPpiProtocolLinker(string com, int slaveAddress)
             : base(com, 9600, Parity.Even, StopBits.One, 8, slaveAddress)
         {
-            ((BaseConnector)BaseConnector).AddController(new MatchController(new ICollection<(int,int)>[] { new List<(int,int)> { (4,5) }, new List<(int,int)> {(5,4) }, new List<(int,int)> { (11 ,11), (12,12) } }, 0));
+            ((BaseConnector)BaseConnector).AddController(new FifoController(0));
         }
 
         /// <summary>
@@ -37,6 +37,7 @@ namespace Modbus.Net.Siemens
                         new ComConfirmMessageSiemensProtocol().Format(inputStruct2));
             }
             var receiveBytes = await SendReceiveWithoutExtAndDecAsync(extBytes);
+            if (receiveBytes == null) return null;
             if (content.Length > 6 && receiveBytes.Length == 1 && receiveBytes[0] == 0xe5)
             {
                 var inputStruct2 = new ComConfirmMessageSiemensInputStruct(content[4], content[5]);
@@ -56,7 +57,7 @@ namespace Modbus.Net.Siemens
         public override async Task<byte[]> SendReceiveWithoutExtAndDecAsync(byte[] content)
         {
             var ans = await base.SendReceiveWithoutExtAndDecAsync(content);
-            while (ans.Length == 1 && ans[0] == 0xf9)
+            while (ans?.Length == 1 && ans[0] == 0xf9)
             {
                 Thread.Sleep(500);
                 if (content.Length <= 6)
diff --git a/Modbus.Net/Modbus.Net.Siemens/SiemensTcpProtocol.cs b/Modbus.Net/Modbus.Net.Siemens/SiemensTcpProtocol.cs
index 15fd6ac..ed24709 100644
--- a/Modbus.Net/Modbus.Net.Siemens/SiemensTcpProtocol.cs
+++ b/Modbus.Net/Modbus.Net.Siemens/SiemensTcpProtocol.cs
@@ -152,10 +152,15 @@ namespace Modbus.Net.Siemens
                 //先建立连接，然后建立设备的引用
                 (await (await
                     ForceSendReceiveAsync(this[typeof(CreateReferenceSiemensProtocol)], inputStruct)).SendReceiveAsync(
-                    this[typeof(EstablishAssociationSiemensProtocol)], answer =>
+                    this[typeof(EstablishAssociationSiemensProtocol)], answer => 
+                    answer != null ?
                         new EstablishAssociationSiemensInputStruct(0x0101, _maxCalling,
                             _maxCalled,
-                            _maxPdu))).Unwrap<EstablishAssociationSiemensOutputStruct>();
+                            _maxPdu) : null)).Unwrap<EstablishAssociationSiemensOutputStruct>();
+            if (outputStruct == null && ProtocolLinker.IsConnected)
+            {
+                ProtocolLinker.Disconnect();
+            }
             return outputStruct != null;
         }
     }
diff --git a/Modbus.Net/Modbus.Net/ProtocalLinker.cs b/Modbus.Net/Modbus.Net/ProtocalLinker.cs
index 91f77d3..e9fd246 100644
--- a/Modbus.Net/Modbus.Net/ProtocalLinker.cs
+++ b/Modbus.Net/Modbus.Net/ProtocalLinker.cs
@@ -66,6 +66,11 @@ namespace Modbus.Net
             return bytesExtend?.BytesDecact(content);
         }
 
+        /// <summary>
+        ///     检查接收的数据是否正确
+        /// </summary>
+        /// <param name="content">接收协议的内容</param>
+        /// <returns>协议是否是正确的</returns>
         public override bool? CheckRight(byte[] content)
         {
             if (content == null)