Release S7NetPlus 0.4.0

Release highlights:
- Adress checks for bit writes
- Support for reading/writing complex objects
- Better exceptions on Open(Async)
- Revert negotiated max PDU size to 960
- Add Logo0BA8 support
- Read/Write-Timeout support on TCP connection
- Fix for 0-padding of last dataItem in WriteMultiple
- Allow override of default port
- Improve exception message when parsing string
- Add DateTime type for reading/writing
- Verify items fit in a PDU on Read/Write-Multiple
- Fix size calculation for bit arrays

GitVersion.yml

@@ -4,14 +4,18 @@ branches:
   master:
     tag: rc
     increment: Minor
-  features?[/-]:
+  feature:
+    regex: features?[/-]
     tag: rc-{BranchName}
     increment: Minor
-  (pull|pull\-requests|pr)[/-]:
+  pull-request:
+    regex: (pull|pull\-requests|pr)[/-]
     tag: rc-pr-{BranchName}
     increment: Minor
-  hotfix(es)?[/-]:
+  hotfix:
+    regex: hotfix(es)?[/-]
     tag: rc
     increment: Patch
-  dev(elop)?(ment)?$:
+  develop:
+    regex: dev(elop)?(ment)?$
     tag: b

S7.Net.UnitTest/ConnectionRequestTest.cs

@@ -75,7 +75,7 @@ namespace S7.Net.UnitTest
                 destTsap1, destTsap2, //Destination TASP
                 192, //Parameter Code (tpdu-size)
                 1, //Parameter Length
-                11 //TPDU Size (2^11 = 2048)
+                10 //TPDU Size (2^11 = 2048)
             };
         }
     }

S7.Net.UnitTest/Helpers/S7TestServer.cs

@@ -9,6 +9,7 @@ namespace S7.Net.UnitTest.Helpers
         static private byte[] DB1 = new byte[1024];  // Our DB1
         static private byte[] DB2 = new byte[64000]; // Our DB2
         static private byte[] DB3 = new byte[1024]; // Our DB3
+        static private byte[] DB4 = new byte[6] { 3, 128, 1, 0, 197, 104 }; // Our DB4
 
         private static S7Server.TSrvCallback TheEventCallBack; // <== Static var containig the callback
         private static S7Server.TSrvCallback TheReadCallBack; // <== Static var containig the callback
@@ -36,9 +37,10 @@ namespace S7.Net.UnitTest.Helpers
                                 1,                   // Its number is 1 (DB1)
                                 DB1,                 // Our buffer for DB1
                                 DB1.Length);         // Its size
-            // Do the same for DB2 and DB3
+            // Do the same for DB2, DB3, and DB4
             Server.RegisterArea(S7Server.srvAreaDB, 2, DB2, DB2.Length);
             Server.RegisterArea(S7Server.srvAreaDB, 3, DB3, DB3.Length);
+            Server.RegisterArea(S7Server.srvAreaDB, 4, DB4, DB4.Length);
 
             // Exclude read event to avoid the double report
             // Set the callbacks (using the static var to avoid the garbage collect)

S7.Net.UnitTest/Helpers/TestClassWithNestedClass.cs

@@ -0,0 +1,51 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace S7.Net.UnitTest.Helpers
+{
+    class TestClassInnerWithBool
+    {
+        public bool BitVariable00 { get; set; }
+    }
+
+    class TestClassInnerWithByte
+    {
+        public byte ByteVariable00 { get; set; }
+    }
+
+    class TestClassInnerWithShort
+    {
+        public short ShortVarialbe00 { get; set; }
+    }
+
+    class TestClassWithNestedClass
+    {
+        /// <summary>
+        /// DB1.DBX0.0
+        /// </summary>
+        public bool BitVariable00 { get; set; }
+
+        /// <summary>
+        /// DB1.DBX0.1
+        /// </summary>
+        public TestClassInnerWithBool BitVariable01 { get; set; } = new TestClassInnerWithBool();
+
+        /// <summary>
+        /// DB1.DBB1.0
+        /// </summary>
+        public TestClassInnerWithByte ByteVariable02 { get; set; } = new TestClassInnerWithByte();
+
+        /// <summary>
+        /// DB1.DBX2.0
+        /// </summary>
+        public bool BitVariable03 { get; set; }
+
+        /// <summary>
+        /// DB1.DBW4
+        /// </summary>
+        public TestClassInnerWithShort ShortVariable04 { get; set; } = new TestClassInnerWithShort();
+    }
+}

S7.Net.UnitTest/S7.Net.UnitTest.csproj

@@ -62,6 +62,7 @@
   <ItemGroup>
     <Compile Include="ConnectionRequestTest.cs" />
     <Compile Include="ConvertersUnitTest.cs" />
+    <Compile Include="Helpers\TestClassWithNestedClass.cs" />
     <Compile Include="ProtocolTests.cs" />
     <Compile Include="Helpers\ConsoleManager.cs" />
     <Compile Include="Helpers\NativeMethods.cs" />
@@ -78,6 +79,7 @@
     <Compile Include="S7NetTestsSync.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Helpers\TestLongStruct.cs" />
+    <Compile Include="TypeTests\DateTimeTests.cs" />
     <Compile Include="TypeTests\StringExTests.cs" />
     <Compile Include="TypeTests\StringTests.cs" />
   </ItemGroup>

S7.Net.UnitTest/S7NetTestsAsync.cs

@@ -160,6 +160,31 @@ namespace S7.Net.UnitTest
             Assert.AreEqual(tc.DWordVariable, tc2.DWordVariable);
         }
 
+        [TestMethod]
+        public async Task Test_Async_ReadAndWriteNestedClass()
+        {
+            Assert.IsTrue(plc.IsConnected, "Before executing this test, the plc must be connected. Check constructor.");
+
+            TestClassWithNestedClass tc = new TestClassWithNestedClass
+            {
+                BitVariable00 = true,
+                BitVariable01 = new TestClassInnerWithBool { BitVariable00 = true },
+                ByteVariable02 = new TestClassInnerWithByte { ByteVariable00 = 128 },
+                BitVariable03 = true,
+                ShortVariable04 = new TestClassInnerWithShort { ShortVarialbe00 = -15000 }
+            };
+
+            await plc.WriteClassAsync(tc, DB4);
+            TestClassWithNestedClass tc2 = new TestClassWithNestedClass();
+            // Values that are read from a class are stored inside the class itself, that is passed by reference
+            await plc.ReadClassAsync(tc2, DB4);
+            Assert.AreEqual(tc.BitVariable00, tc2.BitVariable00);
+            Assert.AreEqual(tc.BitVariable01.BitVariable00, tc2.BitVariable01.BitVariable00);
+            Assert.AreEqual(tc.ByteVariable02.ByteVariable00, tc2.ByteVariable02.ByteVariable00);
+            Assert.AreEqual(tc.BitVariable03, tc2.BitVariable03);
+            Assert.AreEqual(tc.ShortVariable04.ShortVarialbe00, tc2.ShortVariable04.ShortVarialbe00);
+        }
+
         /// <summary>
         /// Read/Write a struct that has the same properties of a DB with the same field in the same order
         /// </summary>
@@ -663,6 +688,28 @@ namespace S7.Net.UnitTest
             }
         }
 
+        [TestMethod]
+        public async Task Test_Async_ReadClassWithNestedClassAfterBit()
+        {
+            Assert.IsTrue(plc.IsConnected, "Before executing this test, the plc must be connected. Check constructor.");
+
+            Assert.AreEqual(6, Types.Class.GetClassSize(new TestClassWithNestedClass()));
+
+            TestClassWithNestedClass tc = new TestClassWithNestedClass();
+            tc.BitVariable00 = true;
+            tc.BitVariable01.BitVariable00 = true;
+            tc.ByteVariable02.ByteVariable00 = 128;
+            tc.BitVariable03 = true;
+            tc.ShortVariable04.ShortVarialbe00 = -15000;
+
+            TestClassWithNestedClass tc2 = await plc.ReadClassAsync<TestClassWithNestedClass>(DB4);
+            Assert.AreEqual(tc.BitVariable00, tc2.BitVariable00);
+            Assert.AreEqual(tc.BitVariable01.BitVariable00, tc2.BitVariable01.BitVariable00);
+            Assert.AreEqual(tc.ByteVariable02.ByteVariable00, tc2.ByteVariable02.ByteVariable00);
+            Assert.AreEqual(tc.BitVariable03, tc2.BitVariable03);
+            Assert.AreEqual(tc.ShortVariable04.ShortVarialbe00, tc2.ShortVariable04.ShortVarialbe00);
+        }
+
         [TestMethod]
         [ExpectedException(typeof(NullReferenceException))]
         public async Task Test_Async_ReadStructThrowsExceptionPlcIsNotConnected()
@@ -737,7 +784,7 @@ namespace S7.Net.UnitTest
             };
             plc.WriteClass(tc, DB2);
 
-            int expectedReadBytes = Types.Class.GetClassSize(tc);
+            int expectedReadBytes = (int)Types.Class.GetClassSize(tc);
 
             TestClass tc2 = new TestClass();
             // Values that are read from a class are stored inside the class itself, that is passed by reference

S7.Net.UnitTest/S7NetTestsSync.cs

@@ -40,6 +40,7 @@ namespace S7.Net.UnitTest
     {
         #region Constants
         const int DB2 = 2;
+        const int DB4 = 4;
         #endregion
 
         #region Private fields
@@ -694,6 +695,54 @@ namespace S7.Net.UnitTest
             }
         }
 
+        [TestMethod]
+        public void T31_ReadClassWithNestedClassAfterBit()
+        {
+            Assert.IsTrue(plc.IsConnected, "Before executing this test, the plc must be connected. Check constructor.");
+
+            Assert.AreEqual(6, Types.Class.GetClassSize(new TestClassWithNestedClass()));
+
+            TestClassWithNestedClass tc = new TestClassWithNestedClass();
+            tc.BitVariable00 = true;
+            tc.BitVariable01.BitVariable00 = true;
+            tc.ByteVariable02.ByteVariable00 = 128;
+            tc.BitVariable03 = true;
+            tc.ShortVariable04.ShortVarialbe00 = -15000;
+
+            TestClassWithNestedClass tc2 = new TestClassWithNestedClass();
+            plc.ReadClass(tc2, DB4);
+            Assert.AreEqual(tc.BitVariable00, tc2.BitVariable00);
+            Assert.AreEqual(tc.BitVariable01.BitVariable00, tc2.BitVariable01.BitVariable00);
+            Assert.AreEqual(tc.ByteVariable02.ByteVariable00, tc2.ByteVariable02.ByteVariable00);
+            Assert.AreEqual(tc.BitVariable03, tc2.BitVariable03);
+            Assert.AreEqual(tc.ShortVariable04.ShortVarialbe00, tc2.ShortVariable04.ShortVarialbe00);
+        }
+
+        [TestMethod]
+        public void T32_ReadAndWriteNestedClass()
+        {
+            Assert.IsTrue(plc.IsConnected, "Before executing this test, the plc must be connected. Check constructor.");
+
+            TestClassWithNestedClass tc = new TestClassWithNestedClass
+            {
+                BitVariable00 = true,
+                BitVariable01 = new TestClassInnerWithBool { BitVariable00 = true },
+                ByteVariable02 = new TestClassInnerWithByte { ByteVariable00 = 128 },
+                BitVariable03 = true,
+                ShortVariable04 = new TestClassInnerWithShort { ShortVarialbe00 = -15000 }
+            };
+
+            plc.WriteClass(tc, DB4);
+            TestClassWithNestedClass tc2 = new TestClassWithNestedClass();
+            // Values that are read from a class are stored inside the class itself, that is passed by reference
+            plc.ReadClass(tc2, DB4);
+            Assert.AreEqual(tc.BitVariable00, tc2.BitVariable00);
+            Assert.AreEqual(tc.BitVariable01.BitVariable00, tc2.BitVariable01.BitVariable00);
+            Assert.AreEqual(tc.ByteVariable02.ByteVariable00, tc2.ByteVariable02.ByteVariable00);
+            Assert.AreEqual(tc.BitVariable03, tc2.BitVariable03);
+            Assert.AreEqual(tc.ShortVariable04.ShortVarialbe00, tc2.ShortVariable04.ShortVarialbe00);
+        }
+
         [TestMethod, ExpectedException(typeof(PlcException))]
         public void T18_ReadStructThrowsIfPlcIsNotConnected()
         {
@@ -767,7 +816,7 @@ namespace S7.Net.UnitTest
             tc.DWordVariable = 850;
             plc.WriteClass(tc, DB2);
 
-            int expectedReadBytes = Types.Class.GetClassSize(tc);
+            int expectedReadBytes = (int)Types.Class.GetClassSize(tc);
 
             TestClass tc2 = new TestClass();
             // Values that are read from a class are stored inside the class itself, that is passed by reference

S7.Net.UnitTest/TypeTests/DateTimeTests.cs

@@ -0,0 +1,176 @@
+using System;
+using System.Linq;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace S7.Net.UnitTest.TypeTests
+{
+    public static class DateTimeTests
+    {
+        private static readonly DateTime SampleDateTime = new DateTime(1993, 12, 25, 8, 12, 34, 567);
+
+        private static readonly byte[] SampleByteArray = {0x93, 0x12, 0x25, 0x08, 0x12, 0x34, 0x56, 7 << 4 | 7};
+
+        private static readonly byte[] SpecMinByteArray =
+        {
+            0x90, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, (byte) (int) (Types.DateTime.SpecMinimumDateTime.DayOfWeek + 1)
+        };
+
+        private static readonly byte[] SpecMaxByteArray =
+        {
+            0x89, 0x12, 0x31, 0x23, 0x59, 0x59, 0x99, (byte) (9 << 4 | (int) (Types.DateTime.SpecMaximumDateTime.DayOfWeek + 1))
+        };
+
+        [TestClass]
+        public class FromByteArray
+        {
+            [TestMethod]
+            public void Sample()
+            {
+                AssertFromByteArrayEquals(SampleDateTime, SampleByteArray);
+            }
+
+            [TestMethod]
+            public void SpecMinimum()
+            {
+                AssertFromByteArrayEquals(Types.DateTime.SpecMinimumDateTime, SpecMinByteArray);
+            }
+
+            [TestMethod]
+            public void SpecMaximum()
+            {
+                AssertFromByteArrayEquals(Types.DateTime.SpecMaximumDateTime, SpecMaxByteArray);
+            }
+
+            [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]
+            public void ThrowsOnLessThan8Bytes()
+            {
+                Types.DateTime.FromByteArray(new byte[7]);
+            }
+
+            [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]
+            public void ThrowsOnMoreTHan8Bytes()
+            {
+                Types.DateTime.FromByteArray(new byte[9]);
+            }
+
+            [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]
+            public void ThrowsOnInvalidYear()
+            {
+                Types.DateTime.FromByteArray(MutateSample(0, 0xa0));
+            }
+
+            [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]
+            public void ThrowsOnZeroMonth()
+            {
+                Types.DateTime.FromByteArray(MutateSample(1, 0x00));
+            }
+
+            [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]
+            public void ThrowsOnTooLargeMonth()
+            {
+                Types.DateTime.FromByteArray(MutateSample(1, 0x13));
+            }
+
+            [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]
+            public void ThrowsOnZeroDay()
+            {
+                Types.DateTime.FromByteArray(MutateSample(2, 0x00));
+            }
+
+            [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]
+            public void ThrowsOnTooLargeDay()
+            {
+                Types.DateTime.FromByteArray(MutateSample(2, 0x32));
+            }
+
+            [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]
+            public void ThrowsOnInvalidHour()
+            {
+                Types.DateTime.FromByteArray(MutateSample(3, 0x24));
+            }
+
+            [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]
+            public void ThrowsOnInvalidMinute()
+            {
+                Types.DateTime.FromByteArray(MutateSample(4, 0x60));
+            }
+
+            [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]
+            public void ThrowsOnInvalidSecond()
+            {
+                Types.DateTime.FromByteArray(MutateSample(5, 0x60));
+            }
+
+            [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]
+            public void ThrowsOnInvalidFirstTwoMillisecondDigits()
+            {
+                Types.DateTime.FromByteArray(MutateSample(6, 0xa0));
+            }
+
+            [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]
+            public void ThrowsOnInvalidThirdMillisecondDigit()
+            {
+                Types.DateTime.FromByteArray(MutateSample(7, 10 << 4));
+            }
+
+            [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]
+            public void ThrowsOnZeroDayOfWeek()
+            {
+                Types.DateTime.FromByteArray(MutateSample(7, 0));
+            }
+
+            [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]
+            public void ThrowsOnTooLargeDayOfWeek()
+            {
+                Types.DateTime.FromByteArray(MutateSample(7, 8));
+            }
+
+            private static void AssertFromByteArrayEquals(DateTime expected, params byte[] bytes)
+            {
+                Assert.AreEqual(expected, Types.DateTime.FromByteArray(bytes));
+            }
+
+            private static byte[] MutateSample(int index, byte value) =>
+                SampleByteArray.Select((b, i) => i == index ? value : b).ToArray();
+        }
+
+        [TestClass]
+        public class ToByteArray
+        {
+            [TestMethod]
+            public void Sample()
+            {
+                AssertToByteArrayEquals(SampleDateTime, SampleByteArray);
+            }
+
+            [TestMethod]
+            public void SpecMinimum()
+            {
+                AssertToByteArrayEquals(Types.DateTime.SpecMinimumDateTime, SpecMinByteArray);
+            }
+
+            [TestMethod]
+            public void SpecMaximum()
+            {
+                AssertToByteArrayEquals(Types.DateTime.SpecMaximumDateTime, SpecMaxByteArray);
+            }
+
+            [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]
+            public void ThrowsOnTimeBeforeSpecMinimum()
+            {
+                Types.DateTime.ToByteArray(new DateTime(1970, 1, 1));
+            }
+
+            [TestMethod, ExpectedException(typeof(ArgumentOutOfRangeException))]
+            public void ThrowsOnTimeAfterSpecMaximum()
+            {
+                Types.DateTime.ToByteArray(new DateTime(2090, 1, 1));
+            }
+
+            private static void AssertToByteArrayEquals(DateTime value, params byte[] expected)
+            {
+                CollectionAssert.AreEqual(expected, Types.DateTime.ToByteArray(value));
+            }
+        }
+    }
+}

S7.Net/COTP.cs

@@ -16,6 +16,7 @@ namespace S7.Net
         /// </summary>
         public class TPDU
         {
+            public TPKT TPkt { get; }
             public byte HeaderLength;
             public byte PDUType;
             public int TPDUNumber;
@@ -24,6 +25,8 @@ namespace S7.Net
 
             public TPDU(TPKT tPKT)
             {
+                TPkt = tPKT;
+
                 var br = new BinaryReader(new MemoryStream(tPKT.Data));
                 HeaderLength = br.ReadByte();
                 if (HeaderLength >= 2)

S7.Net/Enums.cs

@@ -10,6 +10,11 @@
         /// </summary>
         S7200 = 0,
 
+        /// <summary>
+        /// Siemens Logo 0BA8
+        /// </summary>
+        Logo0BA8 = 1,
+
         /// <summary>
         /// S7 300 cpu type
         /// </summary>
@@ -176,6 +181,11 @@
         /// <summary>
         /// Counter variable type
         /// </summary>
-        Counter
+        Counter,
+
+        /// <summary>
+        /// DateTIme variable type
+        /// </summary>
+        DateTime
     }
 }

S7.Net/InvalidDataException.cs

@@ -0,0 +1,43 @@
+using System;
+
+namespace S7.Net
+{
+    #if NET_FULL
+    [Serializable]
+    #endif
+    public class InvalidDataException : Exception
+    {
+        public byte[] ReceivedData { get; }
+        public int ErrorIndex { get; }
+        public byte ExpectedValue { get; }
+
+        public InvalidDataException(string message, byte[] receivedData, int errorIndex, byte expectedValue)
+            : base(FormatMessage(message, receivedData, errorIndex, expectedValue))
+        {
+            ReceivedData = receivedData;
+            ErrorIndex = errorIndex;
+            ExpectedValue = expectedValue;
+        }
+
+        #if NET_FULL
+        protected InvalidDataException(System.Runtime.Serialization.SerializationInfo info,
+            System.Runtime.Serialization.StreamingContext context) : base(info, context)
+        {
+            ReceivedData = (byte[]) info.GetValue(nameof(ReceivedData), typeof(byte[]));
+            ErrorIndex = info.GetInt32(nameof(ErrorIndex));
+            ExpectedValue = info.GetByte(nameof(ExpectedValue));
+        }
+        #endif
+
+        private static string FormatMessage(string message, byte[] receivedData, int errorIndex, byte expectedValue)
+        {
+            if (errorIndex >= receivedData.Length)
+                throw new ArgumentOutOfRangeException(nameof(errorIndex),
+                    $"{nameof(errorIndex)} {errorIndex} is outside the bounds of {nameof(receivedData)} with length {receivedData.Length}.");
+
+            return $"{message} Invalid data received. Expected '{expectedValue}' at index {errorIndex}, " +
+                $"but received {receivedData[errorIndex]}. See the {nameof(ReceivedData)} property " +
+                "for the full message received.";
+        }
+    }
+}

S7.Net/PLC.cs

@@ -1,5 +1,8 @@
 using System;
+using System.Collections.Generic;
+using System.Linq;
 using System.Net.Sockets;
+using S7.Net.Types;
 
 
 namespace S7.Net
@@ -15,11 +18,19 @@ namespace S7.Net
         private TcpClient tcpClient;
         private NetworkStream stream;
 
+        private int readTimeout = System.Threading.Timeout.Infinite;
+        private int writeTimeout = System.Threading.Timeout.Infinite;
+
         /// <summary>
         /// IP address of the PLC
         /// </summary>
         public string IP { get; private set; }
 
+        /// <summary>
+        /// PORT Number of the PLC, default is 102
+        /// </summary>
+        public int Port { get; private set; }
+
         /// <summary>
         /// CPU type of the PLC
         /// </summary>
@@ -39,6 +50,30 @@ namespace S7.Net
         /// Max PDU size this cpu supports
         /// </summary>
         public Int16 MaxPDUSize { get; set; }
+
+        /// <summary>Gets or sets the amount of time that a read operation blocks waiting for data from PLC.</summary>
+        /// <returns>A <see cref="T:System.Int32" /> that specifies the amount of time, in milliseconds, that will elapse before a read operation fails. The default value, <see cref="F:System.Threading.Timeout.Infinite" />, specifies that the read operation does not time out.</returns>
+        public int ReadTimeout
+        {
+            get => readTimeout;
+            set
+            {
+                readTimeout = value;
+                if (tcpClient != null) tcpClient.ReceiveTimeout = readTimeout;
+            }
+        }
+
+        /// <summary>Gets or sets the amount of time that a write operation blocks waiting for data to PLC. </summary>
+        /// <returns>A <see cref="T:System.Int32" /> that specifies the amount of time, in milliseconds, that will elapse before a write operation fails. The default value, <see cref="F:System.Threading.Timeout.Infinite" />, specifies that the write operation does not time out.</returns>
+        public int WriteTimeout
+        {
+            get => writeTimeout;
+            set
+            {
+                writeTimeout = value;
+                if (tcpClient != null) tcpClient.SendTimeout = writeTimeout;
+            }
+        }
         
         /// <summary>
         /// Returns true if a connection to the PLC can be established
@@ -80,7 +115,34 @@ namespace S7.Net
                 catch { return false; }
             }
         }
-        
+
+        /// <summary>
+        /// Creates a PLC object with all the parameters needed for connections.
+        /// For S7-1200 and S7-1500, the default is rack = 0 and slot = 0.
+        /// You need slot > 0 if you are connecting to external ethernet card (CP).
+        /// For S7-300 and S7-400 the default is rack = 0 and slot = 2.
+        /// </summary>
+        /// <param name="cpu">CpuType of the PLC (select from the enum)</param>
+        /// <param name="ip">Ip address of the PLC</param>
+        /// <param name="port">Port address of the PLC, default 102</param>
+        /// <param name="rack">rack of the PLC, usually it's 0, but check in the hardware configuration of Step7 or TIA portal</param>
+        /// <param name="slot">slot of the CPU of the PLC, usually it's 2 for S7300-S7400, 0 for S7-1200 and S7-1500.
+        ///  If you use an external ethernet card, this must be set accordingly.</param>
+        public Plc(CpuType cpu, string ip, int port, Int16 rack, Int16 slot)
+        {
+            if (!Enum.IsDefined(typeof(CpuType), cpu))
+                throw new ArgumentException($"The value of argument '{nameof(cpu)}' ({cpu}) is invalid for Enum type '{typeof(CpuType).Name}'.", nameof(cpu));
+
+            if (string.IsNullOrEmpty(ip))
+                throw new ArgumentException("IP address must valid.", nameof(ip));
+
+            CPU = cpu;
+            IP = ip;
+            Port = port;
+            Rack = rack;
+            Slot = slot;
+            MaxPDUSize = 240;
+        }
         /// <summary>
         /// Creates a PLC object with all the parameters needed for connections.
         /// For S7-1200 and S7-1500, the default is rack = 0 and slot = 0.
@@ -102,10 +164,12 @@ namespace S7.Net
 
             CPU = cpu;
             IP = ip;
+            Port = 102;
             Rack = rack;
             Slot = slot;
             MaxPDUSize = 240;
         }
+
         /// <summary>
         /// Close connection to PLC
         /// </summary>
@@ -117,6 +181,43 @@ namespace S7.Net
             }
         }
 
+        private void AssertPduSizeForRead(ICollection<DataItem> dataItems)
+        {
+            // 12 bytes of header data, 12 bytes of parameter data for each dataItem
+            if ((dataItems.Count + 1) * 12 > MaxPDUSize) throw new Exception("Too many vars requested for read");
+            
+            // 14 bytes of header data, 4 bytes of result data for each dataItem and the actual data
+            if (GetDataLength(dataItems) + dataItems.Count * 4 + 14 > MaxPDUSize) throw new Exception("Too much data requested for read");
+        }
+
+        private void AssertPduSizeForWrite(ICollection<DataItem> dataItems)
+        {
+            // 12 bytes of header data, 18 bytes of parameter data for each dataItem
+            if (dataItems.Count * 18 + 12 > MaxPDUSize) throw new Exception("Too many vars supplied for write");
+
+            // 12 bytes of header data, 16 bytes of data for each dataItem and the actual data
+            if (GetDataLength(dataItems) + dataItems.Count * 16 + 12 > MaxPDUSize)
+                throw new Exception("Too much data supplied for write");
+        }
+
+        private void ConfigureConnection()
+        {
+            if (tcpClient == null)
+            {
+                return;
+            }
+
+            tcpClient.ReceiveTimeout = ReadTimeout;
+            tcpClient.SendTimeout = WriteTimeout;
+        }
+
+        private int GetDataLength(IEnumerable<DataItem> dataItems)
+        {
+            // Odd length variables are 0-padded
+            return dataItems.Select(di => VarTypeToByteLength(di.VarType, di.Count))
+                .Sum(len => (len & 1) == 1 ? len + 1 : len);
+        }
+
         #region IDisposable Support
         private bool disposedValue = false; // To detect redundant calls
 

S7.Net/PLCHelpers.cs

@@ -2,6 +2,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using DateTime = S7.Net.Types.DateTime;
 
 namespace S7.Net
 {
@@ -144,7 +145,16 @@ namespace S7.Net
                     }
                     else
                     {
-                        return Bit.ToBitArray(bytes);
+                        return Bit.ToBitArray(bytes, varCount);
+                    }
+                case VarType.DateTime:
+                    if (varCount == 1)
+                    {
+                        return DateTime.FromByteArray(bytes);
+                    }
+                    else
+                    {
+                        return DateTime.ToArray(bytes);
                     }
                 default:
                     return null;
@@ -162,7 +172,7 @@ namespace S7.Net
             switch (varType)
             {
                 case VarType.Bit:
-                    return varCount; //TODO
+                    return varCount + 7 / 8;
                 case VarType.Byte:
                     return (varCount < 1) ? 1 : varCount;
                 case VarType.String:
@@ -178,6 +188,8 @@ namespace S7.Net
                 case VarType.DInt:
                 case VarType.Real:
                     return varCount * 4;
+                case VarType.DateTime:
+                    return varCount * 8;
                 default:
                     return 0;
             }
@@ -186,7 +198,7 @@ namespace S7.Net
         private byte[] GetS7ConnectionSetup()
         {
             return new byte[] {  3, 0, 0, 25, 2, 240, 128, 50, 1, 0, 0, 255, 255, 0, 8, 0, 0, 240, 0, 0, 3, 0, 3,
-                    7, 128 //Try 1920 PDU Size. Same as libnodave.
+                    3, 192 // Use 960 PDU size
             };
         }
 

S7.Net/PlcAsynchronous.cs

@@ -25,23 +25,27 @@ namespace S7.Net
             var response = await COTP.TPDU.ReadAsync(stream);
             if (response.PDUType != 0xd0) //Connect Confirm
             {
-                throw new WrongNumberOfBytesException("Waiting for COTP connect confirm");
+                throw new InvalidDataException("Error reading Connection Confirm", response.TPkt.Data, 1, 0x0d);
             }
 
             await stream.WriteAsync(GetS7ConnectionSetup(), 0, 25);
 
             var s7data = await COTP.TSDU.ReadAsync(stream);
-            if (s7data == null || s7data[1] != 0x03) //Check for S7 Ack Data
-            {
-                throw new WrongNumberOfBytesException("Waiting for S7 connection setup");
-            }
+            if (s7data == null)
+                throw new WrongNumberOfBytesException("No data received in response to Communication Setup");
+
+            //Check for S7 Ack Data
+            if (s7data[1] != 0x03)
+                throw new InvalidDataException("Error reading Communication Setup response", s7data, 1, 0x03);
+
             MaxPDUSize = (short)(s7data[18] * 256 + s7data[19]);
         }
 
         private async Task ConnectAsync()
         {
             tcpClient = new TcpClient();
-            await tcpClient.ConnectAsync(IP, 102);
+            ConfigureConnection();
+            await tcpClient.ConnectAsync(IP, Port);
             stream = tcpClient.GetStream();
         }
 
@@ -141,7 +145,7 @@ namespace S7.Net
         /// <returns>The number of read bytes</returns>
         public async Task<Tuple<int, object>> ReadClassAsync(object sourceClass, int db, int startByteAdr = 0)
         {
-            int numBytes = Class.GetClassSize(sourceClass);
+            int numBytes = (int)Class.GetClassSize(sourceClass);
             if (numBytes <= 0)
             {
                 throw new Exception("The size of the class is less than 1 byte and therefore cannot be read");
@@ -201,15 +205,10 @@ namespace S7.Net
         /// <param name="dataItems">List of dataitems that contains the list of variables that must be read. Maximum 20 dataitems are accepted.</param>
         public async Task<List<DataItem>> ReadMultipleVarsAsync(List<DataItem> dataItems)
         {
-            int cntBytes = dataItems.Sum(dataItem => VarTypeToByteLength(dataItem.VarType, dataItem.Count));
-
-            //TODO: Figure out how to use MaxPDUSize here
             //Snap7 seems to choke on PDU sizes above 256 even if snap7 
             //replies with bigger PDU size in connection setup.
-            if (dataItems.Count > 20)
-                throw new Exception("Too many vars requested");
-            if (cntBytes > 222)
-                throw new Exception("Too many bytes requested"); // TODO: proper TDU check + split in multiple requests
+            AssertPduSizeForRead(dataItems);
+            
             try
             {
                 // first create the header
@@ -370,8 +369,9 @@ namespace S7.Net
         /// <returns>A task that represents the asynchronous write operation.</returns>
         public async Task WriteClassAsync(object classValue, int db, int startByteAdr = 0)
         {
-            var bytes = Types.Class.ToBytes(classValue).ToList();
-            await WriteBytesAsync(DataType.DataBlock, db, startByteAdr, bytes.ToArray());
+            byte[] bytes = new byte[(int)Class.GetClassSize(classValue)];
+            Types.Class.ToBytes(classValue, bytes);
+            await WriteBytesAsync(DataType.DataBlock, db, startByteAdr, bytes);
         }
 
         private async Task<byte[]> ReadBytesWithSingleRequestAsync(DataType dataType, int db, int startByteAdr, int count)
@@ -405,6 +405,8 @@ namespace S7.Net
         /// <returns>Task that completes when response from PLC is parsed.</returns>
         public async Task WriteAsync(params DataItem[] dataItems)
         {
+            AssertPduSizeForWrite(dataItems);
+
             var message = new ByteArray();
             var length = S7WriteMultiple.CreateRequest(message, dataItems);
             await stream.WriteAsync(message.Array, 0, length).ConfigureAwait(false);

S7.Net/PlcSynchronous.cs

@@ -23,16 +23,19 @@ namespace S7.Net
                 var response = COTP.TPDU.Read(stream);
                 if (response.PDUType != 0xd0) //Connect Confirm
                 {
-                    throw new WrongNumberOfBytesException("Waiting for COTP connect confirm");
+                    throw new InvalidDataException("Error reading Connection Confirm", response.TPkt.Data, 1, 0x0d);
                 }
 
                 stream.Write(GetS7ConnectionSetup(), 0, 25);
 
                 var s7data = COTP.TSDU.Read(stream);
-                if (s7data == null || s7data[1] != 0x03) //Check for S7 Ack Data
-                {
-                    throw new WrongNumberOfBytesException("Waiting for S7 connection setup");
-                }
+                if (s7data == null)
+                    throw new WrongNumberOfBytesException("No data received in response to Communication Setup");
+
+                //Check for S7 Ack Data
+                if (s7data[1] != 0x03)
+                    throw new InvalidDataException("Error reading Communication Setup response", s7data, 1, 0x03);
+
                 MaxPDUSize = (short)(s7data[18] * 256 + s7data[19]);
             }
             catch (Exception exc)
@@ -47,7 +50,8 @@ namespace S7.Net
             try
             {
                 tcpClient = new TcpClient();
-                tcpClient.Connect(IP, 102);
+                ConfigureConnection();
+                tcpClient.Connect(IP, Port);
                 stream = tcpClient.GetStream();
             }
             catch (SocketException sex)
@@ -162,7 +166,7 @@ namespace S7.Net
         /// <returns>The number of read bytes</returns>
         public int ReadClass(object sourceClass, int db, int startByteAdr = 0)
         {
-            int numBytes = Class.GetClassSize(sourceClass);
+            int numBytes = (int)Class.GetClassSize(sourceClass);
             if (numBytes <= 0)
             {
                 throw new Exception("The size of the class is less than 1 byte and therefore cannot be read");
@@ -226,7 +230,7 @@ namespace S7.Net
                 //TODO: Figure out how to use MaxPDUSize here
                 //Snap7 seems to choke on PDU sizes above 256 even if snap7 
                 //replies with bigger PDU size in connection setup.
-                var maxToWrite = Math.Min(count, 200);
+                var maxToWrite = Math.Min(count, MaxPDUSize - 28);//TODO tested only when the MaxPDUSize is 480
                 WriteBytesWithASingleRequest(dataType, db, startByteAdr + localIndex, value.Skip(localIndex).Take(maxToWrite).ToArray());
                 count -= maxToWrite;
                 localIndex += maxToWrite;
@@ -370,6 +374,8 @@ namespace S7.Net
         /// <param name="dataItems">The DataItem(s) to write to the PLC.</param>
         public void Write(params DataItem[] dataItems)
         {
+            AssertPduSizeForWrite(dataItems);
+
             var message = new ByteArray();
             var length = S7WriteMultiple.CreateRequest(message, dataItems);
             stream.Write(message.Array, 0, length);
@@ -388,8 +394,9 @@ namespace S7.Net
                 int packageSize = 35 + value.Length;
                 ByteArray package = new ByteArray(packageSize);
 
-                package.Add(new byte[] { 3, 0, 0 });
-                package.Add((byte)packageSize);
+                package.Add(new byte[] { 3, 0 });
+                //complete package size
+                package.Add(Int.ToByteArray((short)packageSize));
                 package.Add(new byte[] { 2, 0xf0, 0x80, 0x32, 1, 0, 0 });
                 package.Add(Word.ToByteArray((ushort)(varCount - 1)));
                 package.Add(new byte[] { 0, 0x0e });
@@ -474,15 +481,10 @@ namespace S7.Net
         /// <param name="dataItems">List of dataitems that contains the list of variables that must be read. Maximum 20 dataitems are accepted.</param>
         public void ReadMultipleVars(List<DataItem> dataItems)
         {
-            int cntBytes = dataItems.Sum(dataItem => VarTypeToByteLength(dataItem.VarType, dataItem.Count));
-
-            //TODO: Figure out how to use MaxPDUSize here
             //Snap7 seems to choke on PDU sizes above 256 even if snap7 
             //replies with bigger PDU size in connection setup.
-            if (dataItems.Count > 20)
-                throw new Exception("Too many vars requested");
-            if (cntBytes > 222)
-                throw new Exception("Too many bytes requested"); // TODO: proper TDU check + split in multiple requests
+            AssertPduSizeForRead(dataItems);
+
             try
             {
                 // first create the header

S7.Net/Protocol/ConnectionRequest.cs

@@ -21,7 +21,7 @@ namespace S7.Net.Protocol
                     3, 0,   //Destination TASP
                     192,    //Parameter Code (tpdu-size)
                     1,      //Parameter Length
-                    11      //TPDU Size (2^11 = 2048)
+                    10      //TPDU Size (2^10 = 1024)
                 };
 
             switch (cpu)
@@ -34,6 +34,14 @@ namespace S7.Net.Protocol
                     bSend1[17] = 0x10;
                     bSend1[18] = 0x00;
                     break;
+                case CpuType.Logo0BA8:
+                    // These values are taken from NodeS7, it's not verified if these are
+                    // exact requirements to connect to the Logo0BA8.
+                    bSend1[13] = 0x01;
+                    bSend1[14] = 0x00;
+                    bSend1[17] = 0x01;
+                    bSend1[18] = 0x02;
+                    break;
                 case CpuType.S71200:
                 case CpuType.S7300:
                 case CpuType.S7400:

S7.Net/Protocol/S7WriteMultiple.cs

@@ -20,8 +20,11 @@ namespace S7.Net.Protocol
             var dataOffset = paramOffset + paramSize;
             var data = new ByteArray();
 
+            var itemCount = 0;
+
             foreach (var item in dataItems)
             {
+                itemCount++;
                 message.Add(Parameter.Template);
                 var value = Serialization.SerializeDataItem(item);
                 var wordLen = item.Value is bool ? 1 : 2;
@@ -30,33 +33,42 @@ namespace S7.Net.Protocol
                 Serialization.SetWordAt(message, paramOffset + Parameter.Offsets.Amount, (ushort) value.Length);
                 Serialization.SetWordAt(message, paramOffset + Parameter.Offsets.DbNumber, (ushort) item.DB);
                 message[paramOffset + Parameter.Offsets.Area] = (byte) item.DataType;
-                Serialization.SetAddressAt(message, paramOffset + Parameter.Offsets.Address, item.StartByteAdr, item.BitAdr);
-
-                paramOffset += Parameter.Template.Length;
 
                 data.Add(0x00);
                 if (item.Value is bool b)
                 {
+                    if (item.BitAdr > 7)
+                        throw new ArgumentException(
+                            $"Cannot read bit with invalid {nameof(item.BitAdr)} '{item.BitAdr}'.", nameof(dataItems));
+
+                    Serialization.SetAddressAt(message, paramOffset + Parameter.Offsets.Address, item.StartByteAdr,
+                        item.BitAdr);
+
                     data.Add(0x03);
                     data.AddWord(1);
 
-                    data.Add(b ? (byte) 1 : (byte) 0);
-                    data.Add(0);
+                    data.Add(b ? (byte)1 : (byte)0);
+                    if (itemCount != dataItems.Length) { 
+                        data.Add(0);
+                    }
                 }
                 else
                 {
+                    Serialization.SetAddressAt(message, paramOffset + Parameter.Offsets.Address, item.StartByteAdr, 0);
+
                     var len = value.Length;
                     data.Add(0x04);
                     data.AddWord((ushort) (len << 3));
                     data.Add(value);
                     
-                    if ((len & 0b1) == 1)
+                    if ((len & 0b1) == 1 && itemCount != dataItems.Length)
                     {
                         data.Add(0);
                     }
                 }
-            }
 
+                paramOffset += Parameter.Template.Length;
+            }
 
             message.Add(data.Array);
 

S7.Net/Protocol/Serialization.cs

@@ -41,6 +41,8 @@ namespace S7.Net.Protocol
                     return Types.Double.ToByteArray((double)value);
                 case "Single":
                     return Types.Single.ToByteArray((float)value);
+                case "DateTime":
+                    return Types.DateTime.ToByteArray((System.DateTime) value);
                 case "Byte[]":
                     return (byte[])value;
                 case "Int16[]":
@@ -60,6 +62,8 @@ namespace S7.Net.Protocol
                     // if the consumer does not pay attention to string length.
                     var stringVal = (string) value;
                     return Types.String.ToByteArray(stringVal, stringVal.Length);
+                case "DateTime[]":
+                    return Types.DateTime.ToByteArray((System.DateTime[]) value);
                 default:
                     throw new InvalidVariableTypeException();
             }

S7.Net/Types/Bit.cs

@@ -1,4 +1,5 @@
-using System.Collections;
+using System;
+using System.Collections;
 
 namespace S7.Net.Types
 {
@@ -16,12 +17,27 @@ namespace S7.Net.Types
         }
 
         /// <summary>
-        /// Converts an array of bytes to a BitArray
+        /// Converts an array of bytes to a BitArray.
         /// </summary>
-        public static BitArray ToBitArray(byte[] bytes)
+        /// <param name="bytes">The bytes to convert.</param>
+        /// <returns>A BitArray with the same number of bits and equal values as <paramref name="bytes"/>.</returns>
+        public static BitArray ToBitArray(byte[] bytes) => ToBitArray(bytes, bytes.Length * 8);
+
+        /// <summary>
+        /// Converts an array of bytes to a BitArray.
+        /// </summary>
+        /// <param name="bytes">The bytes to convert.</param>
+        /// <param name="length">The number of bits to return.</param>
+        /// <returns>A BitArray with <paramref name="length"/> bits.</returns>
+        public static BitArray ToBitArray(byte[] bytes, int length)
         {
-            BitArray bitArr = new BitArray(bytes);
-            return bitArr;
+            if (length > bytes.Length * 8) throw new ArgumentException($"Not enough data in bytes to return {length} bits.", nameof(bytes));
+
+            var bitArr = new BitArray(bytes);
+            var bools = new bool[length];
+            for (var i = 0; i < length; i++) bools[i] = bitArr[i];
+
+            return new BitArray(bools);
         }
     }
 }

S7.Net/Types/Class.cs

@@ -25,10 +25,8 @@ namespace S7.Net.Types
 
         }
 
-        private static double GetIncreasedNumberOfBytes(double startingNumberOfBytes, Type type)
+        private static double GetIncreasedNumberOfBytes(double numBytes, Type type)
         {
-            double numBytes = startingNumberOfBytes;
-
             switch (type.Name)
             {
                 case "Boolean":
@@ -61,7 +59,7 @@ namespace S7.Net.Types
                     break;
                 default:
                     var propertyClass = Activator.CreateInstance(type);
-                    numBytes += GetClassSize(propertyClass);
+                    numBytes = GetClassSize(propertyClass, numBytes, true);
                     break;
             }
 
@@ -73,10 +71,8 @@ namespace S7.Net.Types
         /// </summary>
         /// <param name="instance">An instance of the class</param>
         /// <returns>the number of bytes</returns>
-        public static int GetClassSize(object instance)
+        public static double GetClassSize(object instance, double numBytes = 0.0, bool isInnerProperty = false)
         {
-            double numBytes = 0.0;
-
             var properties = GetAccessableProperties(instance.GetType());
             foreach (var property in properties)
             {
@@ -99,11 +95,14 @@ namespace S7.Net.Types
                     numBytes = GetIncreasedNumberOfBytes(numBytes, property.PropertyType);
                 }
             }
-            // enlarge numBytes to next even number because S7-Structs in a DB always will be resized to an even byte count
-            numBytes = Math.Ceiling(numBytes);
-            if ((numBytes / 2 - Math.Floor(numBytes / 2.0)) > 0)
-                numBytes++;
-            return (int)numBytes;
+            if (false == isInnerProperty)
+            {
+                // enlarge numBytes to next even number because S7-Structs in a DB always will be resized to an even byte count
+                numBytes = Math.Ceiling(numBytes);
+                if ((numBytes / 2 - Math.Floor(numBytes / 2.0)) > 0)
+                    numBytes++;
+            }
+            return numBytes;
         }
 
         private static object GetPropertyValue(Type propertyType, byte[] bytes, ref double numBytes)
@@ -196,14 +195,8 @@ namespace S7.Net.Types
                     break;
                 default:
                     var propClass = Activator.CreateInstance(propertyType);
-                    var buffer = new byte[GetClassSize(propClass)];
-                    if (buffer.Length > 0)
-                    {
-                        Buffer.BlockCopy(bytes, (int)Math.Ceiling(numBytes), buffer, 0, buffer.Length);
-                        FromBytes(propClass, buffer);
-                        value = propClass;
-                        numBytes += buffer.Length;
-                    }
+                    numBytes = FromBytes(propClass, bytes, numBytes);
+                    value = propClass;
                     break;
             }
 
@@ -215,16 +208,10 @@ namespace S7.Net.Types
         /// </summary>
         /// <param name="sourceClass">The object to fill in the given array of bytes</param>
         /// <param name="bytes">The array of bytes</param>
-        public static void FromBytes(object sourceClass, byte[] bytes)
+        public static double FromBytes(object sourceClass, byte[] bytes, double numBytes = 0, bool isInnerClass = false)
         {
             if (bytes == null)
-                return;
-
-            if (bytes.Length != GetClassSize(sourceClass))
-                return;
-
-            // and decode it
-            double numBytes = 0.0;
+                return numBytes;
 
             var properties = GetAccessableProperties(sourceClass.GetType());
             foreach (var property in properties)
@@ -248,9 +235,11 @@ namespace S7.Net.Types
                         null);
                 }
             }
+
+            return numBytes;
         }
 
-        private static void ToBytes(object propertyValue, byte[] bytes, ref double numBytes)
+        private static double SetBytesFromProperty(object propertyValue, byte[] bytes, double numBytes)
         {
             int bytePos = 0;
             int bitPos = 0;
@@ -293,7 +282,7 @@ namespace S7.Net.Types
                     bytes2 = Single.ToByteArray((float)propertyValue);
                     break;
                 default:
-                    bytes2 = ToBytes(propertyValue);
+                    numBytes = ToBytes(propertyValue, bytes, numBytes);
                     break;
             }
 
@@ -308,6 +297,8 @@ namespace S7.Net.Types
                     bytes[bytePos + bCnt] = bytes2[bCnt];
                 numBytes += bytes2.Length;
             }
+
+            return numBytes;
         }
 
         /// <summary>
@@ -315,12 +306,8 @@ namespace S7.Net.Types
         /// </summary>
         /// <param name="sourceClass">The struct object</param>
         /// <returns>A byte array or null if fails.</returns>
-        public static byte[] ToBytes(object sourceClass)
+        public static double ToBytes(object sourceClass, byte[] bytes, double numBytes = 0.0)
         {
-            int size = GetClassSize(sourceClass);
-            byte[] bytes = new byte[size];
-            double numBytes = 0.0;
-
             var properties = GetAccessableProperties(sourceClass.GetType());
             foreach (var property in properties)
             {
@@ -330,15 +317,15 @@ namespace S7.Net.Types
                     Type elementType = property.PropertyType.GetElementType();
                     for (int i = 0; i < array.Length && numBytes < bytes.Length; i++)
                     {
-                        ToBytes(array.GetValue(i), bytes, ref numBytes);
+                        numBytes = SetBytesFromProperty(array.GetValue(i), bytes, numBytes);
                     }
                 }
                 else
                 {
-                    ToBytes(property.GetValue(sourceClass, null), bytes, ref numBytes);
+                    numBytes = SetBytesFromProperty(property.GetValue(sourceClass, null), bytes, numBytes);
                 }
             }
-            return bytes;
+            return numBytes;
         }
     }
 }

S7.Net/Types/DataItem.cs

@@ -68,7 +68,7 @@ namespace S7.Net.Types
                 DB = dbNumber,
                 VarType = varType,
                 StartByteAdr = startByte,
-                BitAdr = (byte) bitNumber
+                BitAdr = (byte) (bitNumber == -1 ? 0 : bitNumber)
             };
         }
 

S7.Net/Types/DateTime.cs

@@ -0,0 +1,156 @@
+using System;
+using System.Collections.Generic;
+
+namespace S7.Net.Types
+{
+    /// <summary>
+    /// Contains the methods to convert between <see cref="T:System.DateTime"/> and S7 representation of datetime values.
+    /// </summary>
+    public static class DateTime
+    {
+        /// <summary>
+        /// The minimum <see cref="T:System.DateTime"/> value supported by the specification.
+        /// </summary>
+        public static readonly System.DateTime SpecMinimumDateTime = new System.DateTime(1990, 1, 1);
+
+        /// <summary>
+        /// The maximum <see cref="T:System.DateTime"/> value supported by the specification.
+        /// </summary>
+        public static readonly System.DateTime SpecMaximumDateTime = new System.DateTime(2089, 12, 31, 23, 59, 59, 999);
+
+        /// <summary>
+        /// Parses a <see cref="T:System.DateTime"/> value from bytes.
+        /// </summary>
+        /// <param name="bytes">Input bytes read from PLC.</param>
+        /// <returns>A <see cref="T:System.DateTime"/> object representing the value read from PLC.</returns>
+        /// <exception cref="ArgumentOutOfRangeException">Thrown when the length of
+        ///   <paramref name="bytes"/> is not 8 or any value in <paramref name="bytes"/>
+        ///   is outside the valid range of values.</exception>
+        public static System.DateTime FromByteArray(byte[] bytes)
+        {
+            return FromByteArrayImpl(bytes);
+        }
+
+        /// <summary>
+        /// Parses an array of <see cref="T:System.DateTime"/> values from bytes.
+        /// </summary>
+        /// <param name="bytes">Input bytes read from PLC.</param>
+        /// <returns>An array of <see cref="T:System.DateTime"/> objects representing the values read from PLC.</returns>
+        /// <exception cref="ArgumentOutOfRangeException">Thrown when the length of
+        ///   <paramref name="bytes"/> is not a multiple of 8 or any value in
+        ///   <paramref name="bytes"/> is outside the valid range of values.</exception>
+        public static System.DateTime[] ToArray(byte[] bytes)
+        {
+            if (bytes.Length % 8 != 0)
+                throw new ArgumentOutOfRangeException(nameof(bytes), bytes.Length,
+                    $"Parsing an array of DateTime requires a multiple of 8 bytes of input data, input data is '{bytes.Length}' long.");
+
+            var cnt = bytes.Length / 8;
+            var result = new System.DateTime[bytes.Length / 8];
+
+            for (var i = 0; i < cnt; i++)
+                result[i] = FromByteArrayImpl(new ArraySegment<byte>(bytes, i * 8, 8));
+
+            return result;
+        }
+
+        private static System.DateTime FromByteArrayImpl(IList<byte> bytes)
+        {
+            if (bytes.Count != 8)
+                throw new ArgumentOutOfRangeException(nameof(bytes), bytes.Count,
+                    $"Parsing a DateTime requires exactly 8 bytes of input data, input data is {bytes.Count} bytes long.");
+
+            int DecodeBcd(byte input) => 10 * (input >> 4) + (input & 0b00001111);
+
+            int ByteToYear(byte bcdYear)
+            {
+                var input = DecodeBcd(bcdYear);
+                if (input < 90) return input + 2000;
+                if (input < 100) return input + 1900;
+
+                throw new ArgumentOutOfRangeException(nameof(bcdYear), bcdYear,
+                    $"Value '{input}' is higher than the maximum '99' of S7 date and time representation.");
+            }
+
+            int AssertRangeInclusive(int input, byte min, byte max, string field)
+            {
+                if (input < min)
+                    throw new ArgumentOutOfRangeException(nameof(input), input,
+                        $"Value '{input}' is lower than the minimum '{min}' allowed for {field}.");
+                if (input > max)
+                    throw new ArgumentOutOfRangeException(nameof(input), input,
+                        $"Value '{input}' is higher than the maximum '{max}' allowed for {field}.");
+
+                return input;
+            }
+
+            var year = ByteToYear(bytes[0]);
+            var month = AssertRangeInclusive(DecodeBcd(bytes[1]), 1, 12, "month");
+            var day = AssertRangeInclusive(DecodeBcd(bytes[2]), 1, 31, "day of month");
+            var hour = AssertRangeInclusive(DecodeBcd(bytes[3]), 0, 23, "hour");
+            var minute = AssertRangeInclusive(DecodeBcd(bytes[4]), 0, 59, "minute");
+            var second = AssertRangeInclusive(DecodeBcd(bytes[5]), 0, 59, "second");
+            var hsec = AssertRangeInclusive(DecodeBcd(bytes[6]), 0, 99, "first two millisecond digits");
+            var msec = AssertRangeInclusive(bytes[7] >> 4, 0, 9, "third millisecond digit");
+            var dayOfWeek = AssertRangeInclusive(bytes[7] & 0b00001111, 1, 7, "day of week");
+
+            return new System.DateTime(year, month, day, hour, minute, second, hsec * 10 + msec);
+        }
+
+        /// <summary>
+        /// Converts a <see cref="T:System.DateTime"/> value to a byte array.
+        /// </summary>
+        /// <param name="dateTime">The DateTime value to convert.</param>
+        /// <returns>A byte array containing the S7 date time representation of <paramref name="dateTime"/>.</returns>
+        /// <exception cref="ArgumentOutOfRangeException">Thrown when the value of
+        ///   <paramref name="dateTime"/> is before <see cref="P:SpecMinimumDateTime"/>
+        ///   or after <see cref="P:SpecMaximumDateTime"/>.</exception>
+        public static byte[] ToByteArray(System.DateTime dateTime)
+        {
+            byte EncodeBcd(int value)
+            {
+                return (byte) ((value / 10 << 4) | value % 10);
+            }
+
+            if (dateTime < SpecMinimumDateTime)
+                throw new ArgumentOutOfRangeException(nameof(dateTime), dateTime,
+                    $"Date time '{dateTime}' is before the minimum '{SpecMinimumDateTime}' supported in S7 date time representation.");
+
+            if (dateTime > SpecMaximumDateTime)
+                throw new ArgumentOutOfRangeException(nameof(dateTime), dateTime,
+                    $"Date time '{dateTime}' is after the maximum '{SpecMaximumDateTime}' supported in S7 date time representation.");
+
+            byte MapYear(int year) => (byte) (year < 2000 ? year - 1900 : year - 2000);
+
+            int DayOfWeekToInt(DayOfWeek dayOfWeek) => (int) dayOfWeek + 1;
+
+            return new[]
+            {
+                EncodeBcd(MapYear(dateTime.Year)),
+                EncodeBcd(dateTime.Month),
+                EncodeBcd(dateTime.Day),
+                EncodeBcd(dateTime.Hour),
+                EncodeBcd(dateTime.Minute),
+                EncodeBcd(dateTime.Second),
+                EncodeBcd(dateTime.Millisecond / 10),
+                (byte) (dateTime.Millisecond % 10 << 4 | DayOfWeekToInt(dateTime.DayOfWeek))
+            };
+        }
+
+        /// <summary>
+        /// Converts an array of <see cref="T:System.DateTime"/> values to a byte array.
+        /// </summary>
+        /// <param name="dateTimes">The DateTime values to convert.</param>
+        /// <returns>A byte array containing the S7 date time representations of <paramref name="dateTime"/>.</returns>
+        /// <exception cref="ArgumentOutOfRangeException">Thrown when any value of
+        ///   <paramref name="dateTimes"/> is before <see cref="P:SpecMinimumDateTime"/>
+        ///   or after <see cref="P:SpecMaximumDateTime"/>.</exception>
+        public static byte[] ToByteArray(System.DateTime[] dateTimes)
+        {
+            var bytes = new List<byte>(dateTimes.Length * 8);
+            foreach (var dateTime in dateTimes) bytes.AddRange(ToByteArray(dateTime));
+
+            return bytes.ToArray();
+        }
+    }
+}

S7.Net/Types/StringEx.cs

@@ -22,7 +22,17 @@ namespace S7.Net.Types
             int size = bytes[0];
             int length = bytes[1];
 
-            return System.Text.Encoding.ASCII.GetString(bytes, 2, length);
+            try
+            {
+                return Encoding.ASCII.GetString(bytes, 2, length);
+            }
+            catch (Exception e)
+            {
+                throw new PlcException(ErrorCode.ReadData,
+                    $"Failed to parse {VarType.StringEx} from data. Following fields were read: size: '{size}', actual length: '{length}', total number of bytes (including header): '{bytes.Length}'.",
+                    e);
+            }
+            
         }
 
         /// <summary>

appveyor.yml

@@ -3,7 +3,7 @@ configuration: Release
 install:
   - choco install gitversion.portable -y
 before_build:
-  - cmd: gitversion /l console /output buildserver /b %APPVEYOR_REPO_BRANCH%
+  - cmd: gitversion /l console /output buildserver
   - nuget restore
 build_script:
   msbuild /nologo /v:m /p:AssemblyVersion=%GitVersion_AssemblySemVer% /p:FileVersion=%GitVersion_MajorMinorPatch% /p:InformationalVersion=%GitVersion_InformationalVersion% /p:Configuration=%CONFIGURATION% S7.sln