diff --git a/src/IOException.php b/src/IOException.php
new file mode 100644
index 0000000..53e73a9
--- /dev/null
+++ b/src/IOException.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace PHPModbus;
+
+/**
+ * Exception class thrown when a socket operation failure happens.
+ */
+class IOException extends \RuntimeException
+{
+
+}
\ No newline at end of file
diff --git a/src/ModbusException.php b/src/ModbusException.php
new file mode 100644
index 0000000..4436dd7
--- /dev/null
+++ b/src/ModbusException.php
@@ -0,0 +1,10 @@
+<?php
+namespace PHPModbus;
+
+/**
+ * Exception class thrown when a server sends packet with error code. Something is wrong with request.
+ */
+class ModbusException extends \RuntimeException
+{
+
+}
\ No newline at end of file
diff --git a/src/ModbusMaster.php b/src/ModbusMaster.php
index e5c5a84..801fdeb 100644
--- a/src/ModbusMaster.php
+++ b/src/ModbusMaster.php
@@ -3,6 +3,7 @@
 namespace PHPModbus;
 
 use Exception;
+use InvalidArgumentException;
 
 /**
  * Phpmodbus Copyright (c) 2004, 2013 Jan Krakora
@@ -193,13 +194,13 @@ class ModbusMaster
             // UDP socket
             $this->sock = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
         } else {
-            throw new Exception("Unknown socket protocol, should be 'TCP' or 'UDP'");
+            throw new InvalidArgumentException("Unknown socket protocol, should be 'TCP' or 'UDP'");
         }
         // Bind the client socket to a specific local port
         if (strlen($this->client) > 0) {
             $result = socket_bind($this->sock, $this->client, $this->client_port);
             if ($result === false) {
-                throw new Exception(
+                throw new IOException(
                     "socket_bind() failed. Reason: ($result)" .
                     socket_strerror(socket_last_error($this->sock))
                 );
@@ -215,7 +216,7 @@ class ModbusMaster
         // Connect the socket
         $result = @socket_connect($this->sock, $this->host, $this->port);
         if ($result === false) {
-            throw new Exception(
+            throw new IOException(
                 "socket_connect() failed. Reason: ($result)" .
                 socket_strerror(socket_last_error($this->sock))
             );
@@ -349,7 +350,7 @@ class ModbusMaster
             } else {
                 $timeSpentWaiting = microtime(true) - $lastAccess;
                 if ($timeSpentWaiting >= $totalReadTimeout) {
-                    throw new Exception(
+                    throw new IOException(
                         "Watchdog time expired [ $totalReadTimeout sec ]!!! " .
                         "Connection to $this->host:$this->port is not established."
                     );
@@ -435,7 +436,7 @@ class ModbusMaster
                 $failure_str = 'UNDEFINED FAILURE CODE';
             }
             // exception response
-            throw new Exception("Modbus response error code: $failure_code ($failure_str)");
+            throw new ModbusException("Modbus response error code: $failure_code ($failure_str)");
         } else {
             $this->status .= "Modbus response error code: NOERROR\n";
             return true;
diff --git a/tests/ModbusMaster/ModbusExceptionTest.php b/tests/ModbusMaster/ModbusExceptionTest.php
index 0d31651..f1b04fc 100644
--- a/tests/ModbusMaster/ModbusExceptionTest.php
+++ b/tests/ModbusMaster/ModbusExceptionTest.php
@@ -1,6 +1,9 @@
 <?php
 namespace Tests\ModbusMaster;
 
+use InvalidArgumentException;
+use PHPModbus\IOException;
+use PHPModbus\ModbusException;
 use PHPModbus\ModbusMaster;
 use PHPModbus\ModbusMasterTcp;
 
@@ -8,7 +11,7 @@ class ModbusExceptionTest extends MockServerTestCase
 {
     public function testThrowProtocolMismatchException()
     {
-        $this->expectException(\Exception::class);
+        $this->expectException(InvalidArgumentException::class);
         $this->expectExceptionMessage("Unknown socket protocol, should be 'TCP' or 'UDP'");
 
         $modbus = new ModbusMaster('127.0.0.1', 'Mismatch');
@@ -17,7 +20,7 @@ class ModbusExceptionTest extends MockServerTestCase
 
     public function testPortClosedException()
     {
-        $this->expectException(\Exception::class);
+        $this->expectException(IOException::class);
         $this->expectExceptionMessage('socket_connect() failed. Reason: ()No connection could be made because the target machine actively refused it.');
 
         $modbus = new ModbusMasterTcp('127.0.0.1');
@@ -27,7 +30,7 @@ class ModbusExceptionTest extends MockServerTestCase
 
     public function testTimeoutException()
     {
-        $this->expectException(\Exception::class);
+        $this->expectException(\RuntimeException::class);
 
         $mockResponse = '89130000000400010101'; // respond with 1 byte (00000001 bits set) [1]
         static::executeWithMockServer($mockResponse, function ($port) {
@@ -45,7 +48,7 @@ class ModbusExceptionTest extends MockServerTestCase
 
     public function testThrowIllegalDataValueException()
     {
-        $this->expectException(\Exception::class);
+        $this->expectException(ModbusException::class);
         $this->expectExceptionMessage('Modbus response error code: 3 (ILLEGAL DATA VALUE)');
 
         $mockResponse = 'da8700000003008303'; // respond with 1 WORD (2 bytes) [0, 3]