diff --git a/includes/xmlrpc.inc b/includes/xmlrpc.inc
index dc69dd9..8ac79a0 100644
--- a/includes/xmlrpc.inc
+++ b/includes/xmlrpc.inc
@@ -570,7 +570,7 @@ function xmlrpc_base64_get_xml($xmlrpc_base64) {
  * @param $options
  *   (optional) An array of options to pass along to drupal_http_request().
  *
- * @return
+ * @return false|string
  *   A single response (single request) or an array of responses (multicall
  *   request). Each response is the return value of the method, just as if it
  *   has been a local function call, on success, or FALSE on failure. If FALSE
@@ -594,10 +594,18 @@ function _xmlrpc($url, $args, $options = array()) {
   $xmlrpc_request = xmlrpc_request($method, $args);
   // Required options which will replace any that are passed in.
   $options['method'] = 'POST';
-  $options['headers']['Content-Type'] = 'text/xml';
+  $options['headers']['Content-Type'] = 'text/xml; charset=utf-8';
   $options['data'] = $xmlrpc_request->xml;
   $result = drupal_http_request($url, $options);
   if ($result->code != 200) {
+    if ($result->code === 0) {
+      /* @see http://php.net/manual/en/function.stream-socket-client.php
+       *
+       * "If the value returned in errno is 0 and the function returned FALSE,
+       * it is an indication that the error occurred before the connect() call."
+       */
+      $result->code = -32300;
+    }
     xmlrpc_error($result->code, $result->error);
     return FALSE;
   }
diff --git a/modules/simpletest/tests/xmlrpc_test/src/Tests/XmlRpcBasicTest.php b/modules/simpletest/tests/xmlrpc_test/src/Tests/XmlRpcBasicTest.php
index 41adee7..5e6a156 100644
--- a/modules/simpletest/tests/xmlrpc_test/src/Tests/XmlRpcBasicTest.php
+++ b/modules/simpletest/tests/xmlrpc_test/src/Tests/XmlRpcBasicTest.php
@@ -117,7 +117,6 @@ class XmlRpcBasicTest extends XmlRpcTestBase {
     $result = xmlrpc($invalid_endpoint, array('system.listMethods' => array()));
     $this->verboseResult($result);
     $this->assertFalse($result, "Calling an unknown host returns an error condition");
-
     $this->assertEqual(-32300, xmlrpc_errno(), "Calling an unknown host is reported as a transport error.");
     $message = xmlrpc_error_msg();
     $this->assertFalse(empty($message), "Calling an unknown host returns a meaningful error message.");
diff --git a/modules/simpletest/tests/xmlrpc_test/src/Tests/XmlRpcMessagesTest.php b/modules/simpletest/tests/xmlrpc_test/src/Tests/XmlRpcMessagesTest.php
index a9c2125..5a3e466 100644
--- a/modules/simpletest/tests/xmlrpc_test/src/Tests/XmlRpcMessagesTest.php
+++ b/modules/simpletest/tests/xmlrpc_test/src/Tests/XmlRpcMessagesTest.php
@@ -88,7 +88,7 @@ class XmlRpcMessagesTest extends XmlRpcTestBase {
     module_load_include('inc', 'xmlrpc');
     $xmlrpc_request = xmlrpc_request('system.listMethods', array());
 
-    $headers = ['Content-Type' => 'text/xml; charset=utf-8'];
+    $headers = array('Content-Type' => 'text/xml; charset=utf-8');
     $request = new Request('POST', $url, $headers, $xmlrpc_request->xml);
     // These may not be initialized in some exception cases.
     $data = NULL;
diff --git a/modules/simpletest/tests/xmlrpc_test/src/Tests/XmlRpcTestBase.php b/modules/simpletest/tests/xmlrpc_test/src/Tests/XmlRpcTestBase.php
index 3d09b15..97b9a1d 100644
--- a/modules/simpletest/tests/xmlrpc_test/src/Tests/XmlRpcTestBase.php
+++ b/modules/simpletest/tests/xmlrpc_test/src/Tests/XmlRpcTestBase.php
@@ -23,6 +23,13 @@ abstract class XmlRpcTestBase extends \DrupalWebTestCase {
   protected $endPoint;
 
   /**
+   * Are verbose results enabled ?
+   *
+   * @var bool
+   */
+  protected $verbose;
+
+  /**
    * Provides detailed response information if verbose is enabled.
    *
    * @param mixed $result
diff --git a/modules/simpletest/tests/xmlrpc_test/xmlrpc_test.module b/modules/simpletest/tests/xmlrpc_test/xmlrpc_test.module
index 0a80759..c56f186 100644
--- a/modules/simpletest/tests/xmlrpc_test/xmlrpc_test.module
+++ b/modules/simpletest/tests/xmlrpc_test/xmlrpc_test.module
@@ -1,6 +1,19 @@
 <?php
+/**
+ * @file
+ * Test module to support XmlRpcMessagesTest and XmlRpcValidatorTest.
+ */
 
-function xmlrpc_test_array_of_structs_test($array) {
+/**
+ * Test function counting elements occurrences.
+ *
+ * @param array $array
+ *   A hash of values, containing sub-arrays with repeated keys.
+ *
+ * @return int
+ *   The count of values for a repeated key.
+ */
+function xmlrpc_test_array_of_structs_test(array $array) {
   $sum = 0;
   foreach ($array as $struct) {
     if (isset($struct['curly'])) {
@@ -10,6 +23,15 @@ function xmlrpc_test_array_of_structs_test($array) {
   return $sum;
 }
 
+/**
+ * Test function checking entities in string arguments.
+ *
+ * @param string $string
+ *   A string containing escaped characters.
+ *
+ * @return array
+ *   A hash of the count of occurrences of escapes by type.
+ */
 function xmlrpc_test_count_the_entities($string) {
   return array(
     'ctLeftAngleBrackets' => substr_count($string, '<'),
@@ -20,29 +42,111 @@ function xmlrpc_test_count_the_entities($string) {
   );
 }
 
-function xmlrpc_test_easy_struct_test($array) {
+/**
+ * Test function building an array from hash/struct values.
+ *
+ * @param array $array
+ *   A hash of values of any type.
+ *
+ * @return mixed
+ *   An array of values from the source hash.
+ */
+function xmlrpc_test_easy_struct_test(array $array) {
   return $array["curly"] + $array["moe"] + $array["larry"];
 }
 
-function xmlrpc_test_echo_struct_test($array) {
+/**
+ * Test function accepting an array and returning it.
+ *
+ * @param array $array
+ *   A source array.
+ *
+ * @return array
+ *   The same array.
+ */
+function xmlrpc_test_echo_struct_test(array $array) {
   return $array;
 }
 
-function xmlrpc_test_many_types_test($number, $boolean, $string, $double, $dateTime, $base64) {
-  $timestamp = gmmktime($dateTime->hour, $dateTime->minute, $dateTime->second, $dateTime->month, $dateTime->day, $dateTime->year);
-  return array($number, $boolean, $string, $double, xmlrpc_date($timestamp), xmlrpc_Base64($base64));
+/**
+ * Test function accepting multiple parameters of different types.
+ *
+ * @param int $number
+ *   An integer value.
+ * @param bool $boolean
+ *   A boolean value.
+ * @param string $string
+ *   A string value.
+ * @param float $double
+ *   A floating-point value.
+ * @param object $date_time
+ *   A XML-RPC date/time object.
+ * @param string $base64
+ *   A XML-RPC base64 object.
+ *
+ * @return array
+ *   An array combining the arguments.
+ */
+function xmlrpc_test_many_types_test($number, $boolean, $string, $double, $date_time, $base64) {
+  $timestamp = gmmktime($date_time->hour, $date_time->minute, $date_time->second, $date_time->month, $date_time->day, $date_time->year);
+  return array(
+    $number,
+    $boolean,
+    $string,
+    $double,
+    xmlrpc_date($timestamp),
+    xmlrpc_Base64($base64),
+  );
 }
 
-function xmlrpc_test_moderate_size_array_check($array) {
+/**
+ * Test function accepting an array.
+ *
+ * @param array $array
+ *   The source array to operate on.
+ *
+ * @return string
+ *   The first and last values of the array, concatenated.
+ */
+function xmlrpc_test_moderate_size_array_check(array $array) {
   return array_shift($array) . array_pop($array);
 }
 
-function xmlrpc_test_nested_struct_test($array) {
+/**
+ * Test function returning a nested hash/struct.
+ *
+ * @param array $array
+ *   A source data hash.
+ *
+ * @return mixed
+ *   A nested hash combining parts of the source data.
+ */
+function xmlrpc_test_nested_struct_test(array $array) {
   return $array["2000"]["04"]["01"]["larry"] + $array["2000"]["04"]["01"]["moe"] + $array["2000"]["04"]["01"]["curly"];
 }
 
+/**
+ * Test function returning a simple hash/struct.
+ *
+ * @param int $number
+ *   A single number argument.
+ *
+ * @return array
+ *   The incoming number, multiplied by 10, 100, 1000 as hash/struct values.
+ */
 function xmlrpc_test_simple_struct_return_test($number) {
-  return array("times10" => ($number*10), "times100" => ($number*100), "times1000" => ($number*1000));
+  return array(
+    "times10" => ($number * 10),
+    "times100" => ($number * 100),
+    "times1000" => ($number * 1000),
+  );
+}
+
+/**
+ * Echoes http headers to XML-RPC clients.
+ */
+function xmlrpc_test_header_echo() {
+  return getallheaders();
 }
 
 /**
@@ -50,15 +154,16 @@ function xmlrpc_test_simple_struct_return_test($number) {
  */
 function xmlrpc_test_xmlrpc() {
   return array(
-    'validator1.arrayOfStructsTest' => 'xmlrpc_test_arrayOfStructsTest',
-    'validator1.countTheEntities' => 'xmlrpc_test_countTheEntities',
-    'validator1.easyStructTest' => 'xmlrpc_test_easyStructTest',
-    'validator1.echoStructTest' => 'xmlrpc_test_echoStructTest',
-    'validator1.manyTypesTest' => 'xmlrpc_test_manyTypesTest',
-    'validator1.moderateSizeArrayCheck' => 'xmlrpc_test_moderateSizeArrayCheck',
-    'validator1.nestedStructTest' => 'xmlrpc_test_nestedStructTest',
-    'validator1.simpleStructReturnTest' => 'xmlrpc_test_simpleStructReturnTest',
+    'validator1.arrayOfStructsTest' => 'xmlrpc_test_array_of_structs_test',
+    'validator1.countTheEntities' => 'xmlrpc_test_count_the_entities',
+    'validator1.easyStructTest' => 'xmlrpc_test_easy_struct_test',
+    'validator1.echoStructTest' => 'xmlrpc_test_echo_struct_test',
+    'validator1.manyTypesTest' => 'xmlrpc_test_many_types_test',
+    'validator1.moderateSizeArrayCheck' => 'xmlrpc_test_moderate_size_array_check',
+    'validator1.nestedStructTest' => 'xmlrpc_test_nested_struct_test',
+    'validator1.simpleStructReturnTest' => 'xmlrpc_test_simple_struct_return_test',
     'messages.messageSizedInKB' => 'xmlrpc_test_message_sized_in_kb',
+    'test.headerEcho' => 'xmlrpc_test_header_echo',
   );
 }
 
@@ -88,13 +193,15 @@ function xmlrpc_test_xmlrpc_alter(&$services) {
 /**
  * Created a message of the desired size in KB.
  *
- * @param $size
+ * @param int $size
  *   Message size in KB.
+ *
  * @return array
  *   Generated message structure.
  */
 function xmlrpc_test_message_sized_in_kb($size) {
   $message = array();
+  $line = array();
 
   $word = 'abcdefg';