diff --git a/README.md b/README.md
index b7b89dd..20f8a5f 100644
--- a/README.md
+++ b/README.md
@@ -295,7 +295,8 @@ $proxy = new ProxyConnector(
   connection attempt.
   If the authentication details are missing or not accepted by the remote HTTP
   proxy server, it is expected to reject each connection attempt with a
-  `407` (Proxy Authentication Required) response status code.
+  `407` (Proxy Authentication Required) response status code and an exception
+  error code of `SOCKET_EACCES` (13).
 
 #### Advanced secure proxy connections
 
diff --git a/src/ProxyConnector.php b/src/ProxyConnector.php
index ed27b3d..c7801f8 100644
--- a/src/ProxyConnector.php
+++ b/src/ProxyConnector.php
@@ -128,7 +128,7 @@ public function connect($uri)
 
         return $this->connector->connect($proxyUri)->then(function (ConnectionInterface $stream) use ($host, $port, $auth) {
             $deferred = new Deferred(function ($_, $reject) use ($stream) {
-                $reject(new RuntimeException('Operation canceled while waiting for response from proxy'));
+                $reject(new RuntimeException('Connection canceled while waiting for response from proxy (ECONNABORTED)', defined('SOCKET_ECONNABORTED') ? SOCKET_ECONNABORTED : 103));
                 $stream->close();
             });
 
@@ -146,16 +146,19 @@ public function connect($uri)
                     try {
                         $response = Psr7\parse_response(substr($buffer, 0, $pos));
                     } catch (Exception $e) {
-                        $deferred->reject(new RuntimeException('Invalid response received from proxy: ' . $e->getMessage(), 0, $e));
+                        $deferred->reject(new RuntimeException('Invalid response received from proxy (EBADMSG)', defined('SOCKET_EBADMSG') ? SOCKET_EBADMSG: 71, $e));
                         $stream->close();
                         return;
                     }
 
-                    // status must be 2xx
-                    if ($response->getStatusCode() < 200 || $response->getStatusCode() >= 300) {
-                        $deferred->reject(new RuntimeException('Proxy rejected with HTTP error code: ' . $response->getStatusCode() . ' ' . $response->getReasonPhrase(), $response->getStatusCode()));
-                        $stream->close();
-                        return;
+                    if ($response->getStatusCode() === 407) {
+                        // map status code 407 (Proxy Authentication Required) to EACCES
+                        $deferred->reject(new RuntimeException('Proxy denied connection due to invalid authentication ' . $response->getStatusCode() . ' (' . $response->getReasonPhrase() . ') (EACCES)', defined('SOCKET_EACCES') ? SOCKET_EACCES : 13));
+                        return $stream->close();
+                    } elseif ($response->getStatusCode() < 200 || $response->getStatusCode() >= 300) {
+                        // map non-2xx status code to ECONNREFUSED
+                        $deferred->reject(new RuntimeException('Proxy refused connection with HTTP error code ' . $response->getStatusCode() . ' (' . $response->getReasonPhrase() . ') (ECONNREFUSED)', defined('SOCKET_ECONNREFUSED') ? SOCKET_ECONNREFUSED : 111));
+                        return $stream->close();
                     }
 
                     // all okay, resolve with stream instance
@@ -172,23 +175,25 @@ public function connect($uri)
 
                 // stop buffering when 8 KiB have been read
                 if (isset($buffer[8192])) {
-                    $deferred->reject(new RuntimeException('Proxy must not send more than 8 KiB of headers'));
+                    $deferred->reject(new RuntimeException('Proxy must not send more than 8 KiB of headers (EMSGSIZE)', defined('SOCKET_EMSGSIZE') ? SOCKET_EMSGSIZE : 90));
                     $stream->close();
                 }
             };
             $stream->on('data', $fn);
 
             $stream->on('error', function (Exception $e) use ($deferred) {
-                $deferred->reject(new RuntimeException('Stream error while waiting for response from proxy', 0, $e));
+                $deferred->reject(new RuntimeException('Stream error while waiting for response from proxy (EIO)', defined('SOCKET_EIO') ? SOCKET_EIO : 5, $e));
             });
 
             $stream->on('close', function () use ($deferred) {
-                $deferred->reject(new RuntimeException('Connection to proxy lost while waiting for response'));
+                $deferred->reject(new RuntimeException('Connection to proxy lost while waiting for response (ECONNRESET)', defined('SOCKET_ECONNRESET') ? SOCKET_ECONNRESET : 104));
             });
 
             $stream->write("CONNECT " . $host . ":" . $port . " HTTP/1.1\r\nHost: " . $host . ":" . $port . "\r\n" . $auth . "\r\n");
 
             return $deferred->promise();
+        }, function (Exception $e) use ($proxyUri) {
+            throw new RuntimeException('Unable to connect to proxy (ECONNREFUSED)', defined('SOCKET_ECONNREFUSED') ? SOCKET_ECONNREFUSED : 111, $e);
         });
     }
 }
diff --git a/tests/AbstractTestCase.php b/tests/AbstractTestCase.php
index 3250568..632b314 100644
--- a/tests/AbstractTestCase.php
+++ b/tests/AbstractTestCase.php
@@ -37,6 +37,20 @@ protected function expectCallableOnceWith($value)
         return $mock;
     }
 
+    protected function expectCallableOnceWithExceptionCode($code)
+    {
+        $mock = $this->createCallableMock();
+        $mock
+            ->expects($this->once())
+            ->method('__invoke')
+            ->with($this->callback(function ($e) use ($code) {
+                return $e->getCode() === $code;
+            }));
+
+        return $mock;
+    }
+
+
     protected function expectCallableOnceParameter($type)
     {
         $mock = $this->createCallableMock();
diff --git a/tests/FunctionalTest.php b/tests/FunctionalTest.php
index a8f2c04..23273cf 100644
--- a/tests/FunctionalTest.php
+++ b/tests/FunctionalTest.php
@@ -28,13 +28,23 @@ public function setUp()
         $this->dnsConnector = new DnsConnector($this->tcpConnector, $resolver);
     }
 
+    public function testNonListeningSocketRejectsConnection()
+    {
+        $proxy = new ProxyConnector('127.0.0.1:9999', $this->dnsConnector);
+
+        $promise = $proxy->connect('google.com:80');
+
+        $this->setExpectedException('RuntimeException', 'Unable to connect to proxy', SOCKET_ECONNREFUSED);
+        Block\await($promise, $this->loop, 3.0);
+    }
+
     public function testPlainGoogleDoesNotAcceptConnectMethod()
     {
         $proxy = new ProxyConnector('google.com', $this->dnsConnector);
 
         $promise = $proxy->connect('google.com:80');
 
-        $this->setExpectedException('RuntimeException', 'Method Not Allowed', 405);
+        $this->setExpectedException('RuntimeException', '405 (Method Not Allowed)', SOCKET_ECONNREFUSED);
         Block\await($promise, $this->loop, 3.0);
     }
 
@@ -49,7 +59,7 @@ public function testSecureGoogleDoesNotAcceptConnectMethod()
 
         $promise = $proxy->connect('google.com:80');
 
-        $this->setExpectedException('RuntimeException', 'Method Not Allowed', 405);
+        $this->setExpectedException('RuntimeException', '405 (Method Not Allowed)', SOCKET_ECONNREFUSED);
         Block\await($promise, $this->loop, 3.0);
     }
 
@@ -59,7 +69,7 @@ public function testSecureGoogleDoesNotAcceptPlainStream()
 
         $promise = $proxy->connect('google.com:80');
 
-        $this->setExpectedException('RuntimeException', 'Connection to proxy lost');
+        $this->setExpectedException('RuntimeException', 'Connection to proxy lost', SOCKET_ECONNRESET);
         Block\await($promise, $this->loop, 3.0);
     }
 }
diff --git a/tests/ProxyConnectorTest.php b/tests/ProxyConnectorTest.php
index 6f51dea..6b11828 100644
--- a/tests/ProxyConnectorTest.php
+++ b/tests/ProxyConnectorTest.php
@@ -162,6 +162,18 @@ public function testRejectsUriWithNonTcpScheme()
         $promise->then(null, $this->expectCallableOnce());
     }
 
+    public function testRejectsIfConnectorRejects()
+    {
+        $promise = \React\Promise\reject(new \RuntimeException());
+        $this->connector->expects($this->once())->method('connect')->willReturn($promise);
+
+        $proxy = new ProxyConnector('proxy.example.com', $this->connector);
+
+        $promise = $proxy->connect('google.com:80');
+
+        $promise->then(null, $this->expectCallableOnce());
+    }
+
     public function testRejectsAndClosesIfStreamWritesNonHttp()
     {
         $stream = $this->getMockBuilder('React\Socket\Connection')->disableOriginalConstructor()->setMethods(array('close', 'write'))->getMock();
@@ -176,7 +188,7 @@ public function testRejectsAndClosesIfStreamWritesNonHttp()
         $stream->expects($this->once())->method('close');
         $stream->emit('data', array("invalid\r\n\r\n"));
 
-        $promise->then(null, $this->expectCallableOnce());
+        $promise->then(null, $this->expectCallableOnceWithExceptionCode(SOCKET_EBADMSG));
     }
 
     public function testRejectsAndClosesIfStreamWritesTooMuchData()
@@ -193,7 +205,24 @@ public function testRejectsAndClosesIfStreamWritesTooMuchData()
         $stream->expects($this->once())->method('close');
         $stream->emit('data', array(str_repeat('*', 100000)));
 
-        $promise->then(null, $this->expectCallableOnce());
+        $promise->then(null, $this->expectCallableOnceWithExceptionCode(SOCKET_EMSGSIZE));
+    }
+
+    public function testRejectsAndClosesIfStreamReturnsProyAuthenticationRequired()
+    {
+        $stream = $this->getMockBuilder('React\Socket\Connection')->disableOriginalConstructor()->setMethods(array('close', 'write'))->getMock();
+
+        $promise = \React\Promise\resolve($stream);
+        $this->connector->expects($this->once())->method('connect')->willReturn($promise);
+
+        $proxy = new ProxyConnector('proxy.example.com', $this->connector);
+
+        $promise = $proxy->connect('google.com:80');
+
+        $stream->expects($this->once())->method('close');
+        $stream->emit('data', array("HTTP/1.1 407 Proxy Authentication Required\r\n\r\n"));
+
+        $promise->then(null, $this->expectCallableOnceWithExceptionCode(SOCKET_EACCES));
     }
 
     public function testRejectsAndClosesIfStreamReturnsNonSuccess()
@@ -210,7 +239,7 @@ public function testRejectsAndClosesIfStreamReturnsNonSuccess()
         $stream->expects($this->once())->method('close');
         $stream->emit('data', array("HTTP/1.1 403 Not allowed\r\n\r\n"));
 
-        $promise->then(null, $this->expectCallableOnce());
+        $promise->then(null, $this->expectCallableOnceWithExceptionCode(SOCKET_ECONNREFUSED));
     }
 
     public function testResolvesIfStreamReturnsSuccess()
@@ -268,6 +297,6 @@ public function testCancelPromiseWillCloseOpenConnectionAndReject()
 
         $promise->cancel();
 
-        $promise->then(null, $this->expectCallableOnce());
+        $promise->then(null, $this->expectCallableOnceWithExceptionCode(SOCKET_ECONNABORTED));
     }
 }