diff --git a/examples/index.php b/examples/index.php
index 49820d9..f0126e0 100644
--- a/examples/index.php
+++ b/examples/index.php
@@ -15,7 +15,11 @@
 // sudo udevadm control --reload-rules && sudo udevadm trigger
 $deviceURI = '/dev/ttyUSB0'; // do not make this changeable from WEB. This could be serious security risk.
 $isSerialDevice = false; // change to true to enable reading serial devices. this will disable ip/port logic and uses RTU
-if (getenv('MODBUS_SERIAL_ENABLED')) { // can be set from Nginx/Apache fast-cgi conf
+if (getenv('MODBUS_SERIAL_ENABLED')) {
+    // can be set from Nginx/Apache fast-cgi conf
+    // for Nginx add these lines where you PHP is configured:
+    //     fastcgi_param MODBUS_SERIAL_ENABLED true;
+    //     fastcgi_param MODBUS_SERIAL_DEVICE /dev/ttyUSB0;
     $isSerialDevice = filter_var(getenv('MODBUS_SERIAL_ENABLED'), FILTER_VALIDATE_BOOLEAN);
     if ($isSerialDevice && getenv('MODBUS_SERIAL_DEVICE')) {
         $deviceURI = getenv('MODBUS_SERIAL_DEVICE');
diff --git a/src/Packet/ModbusApplicationHeader.php b/src/Packet/ModbusApplicationHeader.php
index 7d4372e..a346d37 100644
--- a/src/Packet/ModbusApplicationHeader.php
+++ b/src/Packet/ModbusApplicationHeader.php
@@ -6,6 +6,7 @@
 
 use ModbusTcpClient\Exception\InvalidArgumentException;
 use ModbusTcpClient\Exception\ModbusException;
+use ModbusTcpClient\Utils\Endian;
 use ModbusTcpClient\Utils\Types;
 
 /**
@@ -100,8 +101,8 @@ public static function parse(string $binaryString): ModbusApplicationHeader
             throw new ModbusException('Data length too short to be valid header!');
         }
 
-        $transactionId = Types::parseUInt16($binaryString[0] . $binaryString[1]);
-        $length = Types::parseUInt16($binaryString[4] . $binaryString[5]);
+        $transactionId = Types::parseUInt16($binaryString[0] . $binaryString[1], Endian::BIG_ENDIAN);
+        $length = Types::parseUInt16($binaryString[4] . $binaryString[5], Endian::BIG_ENDIAN);
         $unitId = Types::parseByte($binaryString[6]);
 
         return new ModbusApplicationHeader(
diff --git a/src/Packet/ModbusFunction/MaskWriteRegisterRequest.php b/src/Packet/ModbusFunction/MaskWriteRegisterRequest.php
index d76e84f..540f269 100644
--- a/src/Packet/ModbusFunction/MaskWriteRegisterRequest.php
+++ b/src/Packet/ModbusFunction/MaskWriteRegisterRequest.php
@@ -93,7 +93,7 @@ public function getORMask(): int
      */
     public function getANDMaskAsWord(): Word
     {
-        return new Word(Types::toInt16($this->andMask));
+        return new Word(Types::toInt16($this->andMask, Endian::BIG_ENDIAN));
     }
 
     /**
@@ -101,7 +101,7 @@ public function getANDMaskAsWord(): Word
      */
     public function getORMaskAsWord(): Word
     {
-        return new Word(Types::toInt16($this->orMask));
+        return new Word(Types::toInt16($this->orMask, Endian::BIG_ENDIAN));
     }
 
     protected function getLengthInternal(): int
diff --git a/src/Packet/ModbusFunction/MaskWriteRegisterResponse.php b/src/Packet/ModbusFunction/MaskWriteRegisterResponse.php
index ae2bee8..5201ef9 100644
--- a/src/Packet/ModbusFunction/MaskWriteRegisterResponse.php
+++ b/src/Packet/ModbusFunction/MaskWriteRegisterResponse.php
@@ -80,7 +80,7 @@ public function getORMask(): int
      */
     public function getANDMaskAsWord(): Word
     {
-        return new Word(Types::toInt16($this->andMask));
+        return new Word(Types::toInt16($this->andMask, Endian::BIG_ENDIAN));
     }
 
     /**
@@ -88,6 +88,6 @@ public function getANDMaskAsWord(): Word
      */
     public function getORMaskAsWord(): Word
     {
-        return new Word(Types::toInt16($this->orMask));
+        return new Word(Types::toInt16($this->orMask, Endian::BIG_ENDIAN));
     }
 }
diff --git a/src/Packet/ProtocolDataUnitRequest.php b/src/Packet/ProtocolDataUnitRequest.php
index 3d72d9c..76b83dc 100644
--- a/src/Packet/ProtocolDataUnitRequest.php
+++ b/src/Packet/ProtocolDataUnitRequest.php
@@ -33,7 +33,7 @@ public function __toString(): string
         return b''
             . $this->getHeader()->__toString()
             . Types::toByte($this->getFunctionCode())
-            . Types::toUint16($this->getStartAddress());
+            . Types::toUint16($this->getStartAddress(), Endian::BIG_ENDIAN);
     }
 
     public function getStartAddress(): int
diff --git a/src/Packet/ResponseFactory.php b/src/Packet/ResponseFactory.php
index e9de28d..d4a7887 100644
--- a/src/Packet/ResponseFactory.php
+++ b/src/Packet/ResponseFactory.php
@@ -16,6 +16,7 @@
 use ModbusTcpClient\Packet\ModbusFunction\WriteMultipleRegistersResponse;
 use ModbusTcpClient\Packet\ModbusFunction\WriteSingleCoilResponse;
 use ModbusTcpClient\Packet\ModbusFunction\WriteSingleRegisterResponse;
+use ModbusTcpClient\Utils\Endian;
 use ModbusTcpClient\Utils\Types;
 
 class ResponseFactory
@@ -40,7 +41,7 @@ public static function parseResponse(string|null $binaryString): ModbusResponse|
             return new ErrorResponse(ModbusApplicationHeader::parse($binaryString), $functionCode, $exceptionCode);
         }
 
-        $transactionId = Types::parseUInt16($binaryString[0] . $binaryString[1]);
+        $transactionId = Types::parseUInt16($binaryString[0] . $binaryString[1], Endian::BIG_ENDIAN);
         $unitId = Types::parseByte($binaryString[6]);
 
         $rawData = substr($binaryString, 8);
diff --git a/src/Packet/StartAddressResponse.php b/src/Packet/StartAddressResponse.php
index 4e2ff5a..ff7efa2 100644
--- a/src/Packet/StartAddressResponse.php
+++ b/src/Packet/StartAddressResponse.php
@@ -4,6 +4,7 @@
 namespace ModbusTcpClient\Packet;
 
 
+use ModbusTcpClient\Utils\Endian;
 use ModbusTcpClient\Utils\Types;
 
 abstract class StartAddressResponse extends ProtocolDataUnit implements ModbusResponse
@@ -16,7 +17,7 @@ abstract class StartAddressResponse extends ProtocolDataUnit implements ModbusRe
     public function __construct(string $rawData, int $unitId = 0, int $transactionId = null)
     {
         parent::__construct($unitId, $transactionId);
-        $this->startAddress = Types::parseUInt16(substr($rawData, 0, 2));
+        $this->startAddress = Types::parseUInt16(substr($rawData, 0, 2), Endian::BIG_ENDIAN);
     }
 
     public function __toString(): string
diff --git a/tests/unit/Packet/ModbusFunction/MaskWriteRegisterRequestTest.php b/tests/unit/Packet/ModbusFunction/MaskWriteRegisterRequestTest.php
index 907146e..e7fe51b 100644
--- a/tests/unit/Packet/ModbusFunction/MaskWriteRegisterRequestTest.php
+++ b/tests/unit/Packet/ModbusFunction/MaskWriteRegisterRequestTest.php
@@ -7,11 +7,22 @@
 use ModbusTcpClient\Packet\ModbusFunction\MaskWriteRegisterRequest;
 use ModbusTcpClient\Packet\ModbusPacket;
 use ModbusTcpClient\Packet\Word;
+use ModbusTcpClient\Utils\Endian;
 use ModbusTcpClient\Utils\Types;
 use PHPUnit\Framework\TestCase;
 
 class MaskWriteRegisterRequestTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testOnPacketToString()
     {
         // Field:                    Size in packet
diff --git a/tests/unit/Packet/ModbusFunction/MaskWriteRegisterResponseTest.php b/tests/unit/Packet/ModbusFunction/MaskWriteRegisterResponseTest.php
index 688ffff..eff852d 100644
--- a/tests/unit/Packet/ModbusFunction/MaskWriteRegisterResponseTest.php
+++ b/tests/unit/Packet/ModbusFunction/MaskWriteRegisterResponseTest.php
@@ -5,10 +5,21 @@
 use ModbusTcpClient\Packet\ModbusFunction\MaskWriteRegisterResponse;
 use ModbusTcpClient\Packet\ModbusPacket;
 use ModbusTcpClient\Packet\Word;
+use ModbusTcpClient\Utils\Endian;
 use PHPUnit\Framework\TestCase;
 
 class MaskWriteRegisterResponseTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testOnPacketToString()
     {
         // Field:                    Size in packet
diff --git a/tests/unit/Packet/ModbusFunction/ReadCoilsRequestTest.php b/tests/unit/Packet/ModbusFunction/ReadCoilsRequestTest.php
index e06f76d..128b3ac 100644
--- a/tests/unit/Packet/ModbusFunction/ReadCoilsRequestTest.php
+++ b/tests/unit/Packet/ModbusFunction/ReadCoilsRequestTest.php
@@ -6,10 +6,21 @@
 use ModbusTcpClient\Packet\ErrorResponse;
 use ModbusTcpClient\Packet\ModbusFunction\ReadCoilsRequest;
 use ModbusTcpClient\Packet\ModbusPacket;
+use ModbusTcpClient\Utils\Endian;
 use PHPUnit\Framework\TestCase;
 
 class ReadCoilsRequestTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testPacketToString()
     {
         $this->assertEquals(
diff --git a/tests/unit/Packet/ModbusFunction/ReadCoilsResponseTest.php b/tests/unit/Packet/ModbusFunction/ReadCoilsResponseTest.php
index 25cd788..6d4ddd0 100644
--- a/tests/unit/Packet/ModbusFunction/ReadCoilsResponseTest.php
+++ b/tests/unit/Packet/ModbusFunction/ReadCoilsResponseTest.php
@@ -7,10 +7,21 @@
 use ModbusTcpClient\Exception\ParseException;
 use ModbusTcpClient\Packet\ModbusFunction\ReadCoilsResponse;
 use ModbusTcpClient\Packet\ModbusPacket;
+use ModbusTcpClient\Utils\Endian;
 use PHPUnit\Framework\TestCase;
 
 class ReadCoilsResponseTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testPacketToString()
     {
         $this->assertEquals(
@@ -18,6 +29,7 @@ public function testPacketToString()
             (new ReadCoilsResponse("\x02\xCD\x6B", 3, 33152))->__toString()
         );
     }
+
     public function testToHex()
     {
         $this->assertEquals(
diff --git a/tests/unit/Packet/ModbusFunction/ReadHoldingRegistersRequestTest.php b/tests/unit/Packet/ModbusFunction/ReadHoldingRegistersRequestTest.php
index 6e85e98..e40edd5 100644
--- a/tests/unit/Packet/ModbusFunction/ReadHoldingRegistersRequestTest.php
+++ b/tests/unit/Packet/ModbusFunction/ReadHoldingRegistersRequestTest.php
@@ -6,6 +6,7 @@
 use ModbusTcpClient\Packet\ErrorResponse;
 use ModbusTcpClient\Packet\ModbusFunction\ReadHoldingRegistersRequest;
 use ModbusTcpClient\Packet\ModbusPacket;
+use ModbusTcpClient\Utils\Endian;
 use PHPUnit\Framework\TestCase;
 
 /*
@@ -25,6 +26,16 @@
 
 class ReadHoldingRegistersRequestTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testPacketToString()
     {
         $this->assertEquals(
diff --git a/tests/unit/Packet/ModbusFunction/ReadHoldingRegistersResponseTest.php b/tests/unit/Packet/ModbusFunction/ReadHoldingRegistersResponseTest.php
index 6e40af2..c0d387e 100644
--- a/tests/unit/Packet/ModbusFunction/ReadHoldingRegistersResponseTest.php
+++ b/tests/unit/Packet/ModbusFunction/ReadHoldingRegistersResponseTest.php
@@ -7,10 +7,21 @@
 use ModbusTcpClient\Exception\ParseException;
 use ModbusTcpClient\Packet\ModbusFunction\ReadHoldingRegistersResponse;
 use ModbusTcpClient\Packet\ModbusPacket;
+use ModbusTcpClient\Utils\Endian;
 use PHPUnit\Framework\TestCase;
 
 class ReadHoldingRegistersResponseTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testPacketToString()
     {
         $this->assertEquals(
@@ -341,7 +352,7 @@ public function testGetAsciiString()
         $packet = (new ReadHoldingRegistersResponse("\x08\x01\x00\xF8\x53\x65\x72\x00\x6E", 3, 33152))->withStartAddress(50);
         $this->assertCount(4, $packet->getWords());
 
-        $this->assertEquals('Søren', $packet->getAsciiStringAt(51, 5));
+        $this->assertEquals('Søren', $packet->getAsciiStringAt(51, 5, Endian::BIG_ENDIAN_LOW_WORD_FIRST));
     }
 
     public function testGetAsciiStringInvalidAddressLow()
diff --git a/tests/unit/Packet/ModbusFunction/ReadInputDiscretesRequestTest.php b/tests/unit/Packet/ModbusFunction/ReadInputDiscretesRequestTest.php
index 1485e9c..dce3099 100644
--- a/tests/unit/Packet/ModbusFunction/ReadInputDiscretesRequestTest.php
+++ b/tests/unit/Packet/ModbusFunction/ReadInputDiscretesRequestTest.php
@@ -5,10 +5,21 @@
 use ModbusTcpClient\Packet\ErrorResponse;
 use ModbusTcpClient\Packet\ModbusFunction\ReadInputDiscretesRequest;
 use ModbusTcpClient\Packet\ModbusPacket;
+use ModbusTcpClient\Utils\Endian;
 use PHPUnit\Framework\TestCase;
 
 class ReadInputDiscretesRequestTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testPacketToString()
     {
         $this->assertEquals(
diff --git a/tests/unit/Packet/ModbusFunction/ReadInputDiscretesResponseTest.php b/tests/unit/Packet/ModbusFunction/ReadInputDiscretesResponseTest.php
index 1588993..ce1fe7b 100644
--- a/tests/unit/Packet/ModbusFunction/ReadInputDiscretesResponseTest.php
+++ b/tests/unit/Packet/ModbusFunction/ReadInputDiscretesResponseTest.php
@@ -5,10 +5,21 @@
 use ModbusTcpClient\Exception\ParseException;
 use ModbusTcpClient\Packet\ModbusFunction\ReadInputDiscretesResponse;
 use ModbusTcpClient\Packet\ModbusPacket;
+use ModbusTcpClient\Utils\Endian;
 use PHPUnit\Framework\TestCase;
 
 class ReadInputDiscretesResponseTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testPacketToString()
     {
         $this->assertEquals(
diff --git a/tests/unit/Packet/ModbusFunction/ReadInputRegistersRequestTest.php b/tests/unit/Packet/ModbusFunction/ReadInputRegistersRequestTest.php
index 9f4291d..5b5ae24 100644
--- a/tests/unit/Packet/ModbusFunction/ReadInputRegistersRequestTest.php
+++ b/tests/unit/Packet/ModbusFunction/ReadInputRegistersRequestTest.php
@@ -6,10 +6,21 @@
 use ModbusTcpClient\Packet\ErrorResponse;
 use ModbusTcpClient\Packet\ModbusFunction\ReadInputRegistersRequest;
 use ModbusTcpClient\Packet\ModbusPacket;
+use ModbusTcpClient\Utils\Endian;
 use PHPUnit\Framework\TestCase;
 
 class ReadInputRegistersRequestTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testPacketToString()
     {
         $this->assertEquals(
diff --git a/tests/unit/Packet/ModbusFunction/ReadInputRegistersResponseTest.php b/tests/unit/Packet/ModbusFunction/ReadInputRegistersResponseTest.php
index c68f98e..d29e95f 100644
--- a/tests/unit/Packet/ModbusFunction/ReadInputRegistersResponseTest.php
+++ b/tests/unit/Packet/ModbusFunction/ReadInputRegistersResponseTest.php
@@ -5,10 +5,21 @@
 use ModbusTcpClient\Exception\ParseException;
 use ModbusTcpClient\Packet\ModbusFunction\ReadInputRegistersResponse;
 use ModbusTcpClient\Packet\ModbusPacket;
+use ModbusTcpClient\Utils\Endian;
 use PHPUnit\Framework\TestCase;
 
 class ReadInputRegistersResponseTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testPacketToString()
     {
         $this->assertEquals(
diff --git a/tests/unit/Packet/ModbusFunction/ReadWriteMultipleRegistersRequestTest.php b/tests/unit/Packet/ModbusFunction/ReadWriteMultipleRegistersRequestTest.php
index 50c8edc..e47ff5f 100644
--- a/tests/unit/Packet/ModbusFunction/ReadWriteMultipleRegistersRequestTest.php
+++ b/tests/unit/Packet/ModbusFunction/ReadWriteMultipleRegistersRequestTest.php
@@ -6,11 +6,22 @@
 use ModbusTcpClient\Packet\ErrorResponse;
 use ModbusTcpClient\Packet\ModbusFunction\ReadWriteMultipleRegistersRequest;
 use ModbusTcpClient\Packet\ModbusPacket;
+use ModbusTcpClient\Utils\Endian;
 use ModbusTcpClient\Utils\Types;
 use PHPUnit\Framework\TestCase;
 
 class ReadWriteMultipleRegistersRequestTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testOnPacketToString()
     {
         // Field:                    Size in packet
@@ -32,7 +43,7 @@ public function testOnPacketToString()
                 0x0410,
                 1,
                 0x0112,
-                [Types::toByte(200), Types::toInt16(130)],
+                [Types::toByte(200), Types::toInt16(130, Endian::BIG_ENDIAN_LOW_WORD_FIRST)],
                 0x11,
                 0x0138
             ))->__toString()
@@ -176,7 +187,7 @@ public function testParse()
             0x0410,
             1,
             0x0112,
-            [Types::toByte(200), Types::toInt16(130)],
+            [Types::toByte(200), Types::toInt16(130, Endian::BIG_ENDIAN_LOW_WORD_FIRST)],
             0x11,
             0x0138
         ))->__toString());
diff --git a/tests/unit/Packet/ModbusFunction/ReadWriteMultipleRegistersResponseTest.php b/tests/unit/Packet/ModbusFunction/ReadWriteMultipleRegistersResponseTest.php
index 89d75c7..bf42637 100644
--- a/tests/unit/Packet/ModbusFunction/ReadWriteMultipleRegistersResponseTest.php
+++ b/tests/unit/Packet/ModbusFunction/ReadWriteMultipleRegistersResponseTest.php
@@ -7,10 +7,21 @@
 use ModbusTcpClient\Exception\ParseException;
 use ModbusTcpClient\Packet\ModbusFunction\ReadWriteMultipleRegistersResponse;
 use ModbusTcpClient\Packet\ModbusPacket;
+use ModbusTcpClient\Utils\Endian;
 use PHPUnit\Framework\TestCase;
 
 class ReadWriteMultipleRegistersResponseTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testPacketToString()
     {
         $this->assertEquals(
@@ -341,7 +352,7 @@ public function testGetAsciiString()
         $packet = (new ReadWriteMultipleRegistersResponse("\x08\x01\x00\xF8\x53\x65\x72\x00\x6E", 3, 33152))->withStartAddress(50);
         $this->assertCount(4, $packet->getWords());
 
-        $this->assertEquals('Søren', $packet->getAsciiStringAt(51, 5));
+        $this->assertEquals('Søren', $packet->getAsciiStringAt(51, 5, Endian::BIG_ENDIAN_LOW_WORD_FIRST));
     }
 
     public function testGetAsciiStringInvalidAddressLow()
diff --git a/tests/unit/Packet/ModbusFunction/WriteMultipleCoilsRequestTest.php b/tests/unit/Packet/ModbusFunction/WriteMultipleCoilsRequestTest.php
index cbdc5c4..8162cca 100644
--- a/tests/unit/Packet/ModbusFunction/WriteMultipleCoilsRequestTest.php
+++ b/tests/unit/Packet/ModbusFunction/WriteMultipleCoilsRequestTest.php
@@ -6,10 +6,21 @@
 use ModbusTcpClient\Packet\ErrorResponse;
 use ModbusTcpClient\Packet\ModbusFunction\WriteMultipleCoilsRequest;
 use ModbusTcpClient\Packet\ModbusPacket;
+use ModbusTcpClient\Utils\Endian;
 use PHPUnit\Framework\TestCase;
 
 class WriteMultipleCoilsRequestTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testOnPacketToString()
     {
         $this->assertEquals(
diff --git a/tests/unit/Packet/ModbusFunction/WriteMultipleCoilsResponseTest.php b/tests/unit/Packet/ModbusFunction/WriteMultipleCoilsResponseTest.php
index 683e88d..02f1508 100644
--- a/tests/unit/Packet/ModbusFunction/WriteMultipleCoilsResponseTest.php
+++ b/tests/unit/Packet/ModbusFunction/WriteMultipleCoilsResponseTest.php
@@ -3,12 +3,23 @@
 namespace Tests\Packet\ModbusFunction;
 
 
-use ModbusTcpClient\Packet\ModbusPacket;
 use ModbusTcpClient\Packet\ModbusFunction\WriteMultipleCoilsResponse;
+use ModbusTcpClient\Packet\ModbusPacket;
+use ModbusTcpClient\Utils\Endian;
 use PHPUnit\Framework\TestCase;
 
 class WriteMultipleCoilsResponseTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testOnPacketToString()
     {
         $this->assertEquals(
diff --git a/tests/unit/Packet/ModbusFunction/WriteMultipleRegistersRequestTest.php b/tests/unit/Packet/ModbusFunction/WriteMultipleRegistersRequestTest.php
index f95905f..1a24596 100644
--- a/tests/unit/Packet/ModbusFunction/WriteMultipleRegistersRequestTest.php
+++ b/tests/unit/Packet/ModbusFunction/WriteMultipleRegistersRequestTest.php
@@ -6,11 +6,22 @@
 use ModbusTcpClient\Packet\ErrorResponse;
 use ModbusTcpClient\Packet\ModbusFunction\WriteMultipleRegistersRequest;
 use ModbusTcpClient\Packet\ModbusPacket;
+use ModbusTcpClient\Utils\Endian;
 use ModbusTcpClient\Utils\Types;
 use PHPUnit\Framework\TestCase;
 
 class WriteMultipleRegistersRequestTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testPacketToString()
     {
         // Field:                   Size in packet
@@ -27,7 +38,11 @@ public function testPacketToString()
         // registers: 00c8 0082 8701 (3 registers = 6 bytes)
         $this->assertEquals(
             "\x01\x38\x00\x00\x00\x0d\x11\x10\x04\x10\x00\x03\x06\x00\xC8\x00\x82\x87\x01",
-            (new WriteMultipleRegistersRequest(0x0410, [Types::toByte(200), Types::toInt16(130), Types::toUint16(34561)], 0x11, 0x0138))->__toString()
+            (new WriteMultipleRegistersRequest(0x0410, [
+                Types::toByte(200),
+                Types::toInt16(130, Endian::BIG_ENDIAN_LOW_WORD_FIRST),
+                Types::toUint16(34561, Endian::BIG_ENDIAN_LOW_WORD_FIRST)
+            ], 0x11, 0x0138))->__toString()
         );
     }
 
@@ -57,7 +72,11 @@ public function testPacketProperties()
     public function testParse()
     {
         $packet = WriteMultipleRegistersRequest::parse("\x01\x38\x00\x00\x00\x0d\x11\x10\x04\x10\x00\x03\x06\x00\xC8\x00\x82\x87\x01");
-        $this->assertEquals($packet, (new WriteMultipleRegistersRequest(0x0410, [Types::toByte(200), Types::toInt16(130), Types::toUint16(34561)], 0x11, 0x0138))->__toString());
+        $this->assertEquals($packet, (new WriteMultipleRegistersRequest(0x0410, [
+            Types::toByte(200),
+            Types::toInt16(130, Endian::BIG_ENDIAN_LOW_WORD_FIRST),
+            Types::toUint16(34561, Endian::BIG_ENDIAN_LOW_WORD_FIRST)
+        ], 0x11, 0x0138))->__toString());
         $this->assertEquals(0x0410, $packet->getStartAddress());
         $this->assertEquals(["\x00\xC8", "\x00\x82", "\x87\x01"], $packet->getRegisters());
 
diff --git a/tests/unit/Packet/ModbusFunction/WriteMultipleRegistersResponseTest.php b/tests/unit/Packet/ModbusFunction/WriteMultipleRegistersResponseTest.php
index 4447379..d220dab 100644
--- a/tests/unit/Packet/ModbusFunction/WriteMultipleRegistersResponseTest.php
+++ b/tests/unit/Packet/ModbusFunction/WriteMultipleRegistersResponseTest.php
@@ -3,12 +3,23 @@
 namespace Tests\Packet\ModbusFunction;
 
 
-use ModbusTcpClient\Packet\ModbusPacket;
 use ModbusTcpClient\Packet\ModbusFunction\WriteMultipleRegistersResponse;
+use ModbusTcpClient\Packet\ModbusPacket;
+use ModbusTcpClient\Utils\Endian;
 use PHPUnit\Framework\TestCase;
 
 class WriteMultipleRegistersResponseTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testOnPacketToString()
     {
         $this->assertEquals(
diff --git a/tests/unit/Packet/ModbusFunction/WriteSingleCoilRequestTest.php b/tests/unit/Packet/ModbusFunction/WriteSingleCoilRequestTest.php
index b4606ae..e4f84ae 100644
--- a/tests/unit/Packet/ModbusFunction/WriteSingleCoilRequestTest.php
+++ b/tests/unit/Packet/ModbusFunction/WriteSingleCoilRequestTest.php
@@ -5,10 +5,21 @@
 use ModbusTcpClient\Packet\ErrorResponse;
 use ModbusTcpClient\Packet\ModbusFunction\WriteSingleCoilRequest;
 use ModbusTcpClient\Packet\ModbusPacket;
+use ModbusTcpClient\Utils\Endian;
 use PHPUnit\Framework\TestCase;
 
 class WriteSingleCoilRequestTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testOnPacketToString()
     {
         $this->assertEquals(
diff --git a/tests/unit/Packet/ModbusFunction/WriteSingleCoilResponseTest.php b/tests/unit/Packet/ModbusFunction/WriteSingleCoilResponseTest.php
index bf5ec11..c28611e 100644
--- a/tests/unit/Packet/ModbusFunction/WriteSingleCoilResponseTest.php
+++ b/tests/unit/Packet/ModbusFunction/WriteSingleCoilResponseTest.php
@@ -1,13 +1,25 @@
 <?php
+
 namespace Tests\Packet\ModbusFunction;
 
 
-use ModbusTcpClient\Packet\ModbusPacket;
 use ModbusTcpClient\Packet\ModbusFunction\WriteSingleCoilResponse;
+use ModbusTcpClient\Packet\ModbusPacket;
+use ModbusTcpClient\Utils\Endian;
 use PHPUnit\Framework\TestCase;
 
 class WriteSingleCoilResponseTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testPacketToString()
     {
         $this->assertEquals(
diff --git a/tests/unit/Packet/ModbusFunction/WriteSingleRegisterRequestTest.php b/tests/unit/Packet/ModbusFunction/WriteSingleRegisterRequestTest.php
index 31eb838..02d9f6e 100644
--- a/tests/unit/Packet/ModbusFunction/WriteSingleRegisterRequestTest.php
+++ b/tests/unit/Packet/ModbusFunction/WriteSingleRegisterRequestTest.php
@@ -6,10 +6,21 @@
 use ModbusTcpClient\Packet\ErrorResponse;
 use ModbusTcpClient\Packet\ModbusFunction\WriteSingleRegisterRequest;
 use ModbusTcpClient\Packet\ModbusPacket;
+use ModbusTcpClient\Utils\Endian;
 use PHPUnit\Framework\TestCase;
 
 class WriteSingleRegisterRequestTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testPacketToString()
     {
         $this->assertEquals(
diff --git a/tests/unit/Packet/ModbusFunction/WriteSingleRegisterResponseTest.php b/tests/unit/Packet/ModbusFunction/WriteSingleRegisterResponseTest.php
index a23c794..617e018 100644
--- a/tests/unit/Packet/ModbusFunction/WriteSingleRegisterResponseTest.php
+++ b/tests/unit/Packet/ModbusFunction/WriteSingleRegisterResponseTest.php
@@ -5,10 +5,21 @@
 
 use ModbusTcpClient\Packet\ModbusFunction\WriteSingleRegisterResponse;
 use ModbusTcpClient\Packet\ModbusPacket;
+use ModbusTcpClient\Utils\Endian;
 use PHPUnit\Framework\TestCase;
 
 class WriteSingleRegisterResponseTest extends TestCase
 {
+    protected function setUp(): void
+    {
+        Endian::$defaultEndian = Endian::LITTLE_ENDIAN; // packets are big endian. setting to default to little should not change output
+    }
+
+    protected function tearDown(): void
+    {
+        Endian::$defaultEndian = Endian::BIG_ENDIAN_LOW_WORD_FIRST;
+    }
+
     public function testPacketToString()
     {
         $this->assertEquals(
@@ -22,7 +33,7 @@ public function testOnPacketProperties()
         $packet = new WriteSingleRegisterResponse("\x00\x02\xFF\x00", 3, 33152);
         $this->assertEquals(ModbusPacket::WRITE_SINGLE_REGISTER, $packet->getFunctionCode());
 
-        $this->assertEquals(0xFF00, $packet->getWord()->getUInt16());
+        $this->assertEquals(0xFF00, $packet->getWord()->getUInt16(Endian::BIG_ENDIAN_LOW_WORD_FIRST));
 
         $header = $packet->getHeader();
         $this->assertEquals(33152, $header->getTransactionId());