Add support for Unix domain sockets (UDS)

README.md

@@ -66,3 +66,18 @@ $secureConnector->create('www.google.com', 443)->then(function (React\Stream\Str
 
 $loop->run();
 ```
+
+### Unix domain sockets
+
+Similarly, the `UnixConnector` class can be used to connect to Unix domain socket (UDS)
+paths like this:
+
+```php
+$connector = new React\SocketClient\UnixConnector($loop);
+
+$connector->create('/tmp/demo.sock')->then(function (React\Stream\Stream $stream) {
+    $stream->write("HELLO\n");
+});
+
+$loop->run();
+```

src/UnixConnector.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace React\SocketClient;
+
+use React\SocketClient\ConnectorInterface;
+use React\Stream\Stream;
+use React\EventLoop\LoopInterface;
+use React\Promise;
+use RuntimeException;
+
+/**
+ * Unix domain socket connector
+ *
+ * Unix domain sockets use atomic operations, so we can as well emulate
+ * async behavior.
+ */
+class UnixConnector implements ConnectorInterface
+{
+    private $loop;
+
+    public function __construct(LoopInterface $loop)
+    {
+        $this->loop = $loop;
+    }
+
+    public function create($path, $unusedPort = 0)
+    {
+        $resource = @stream_socket_client('unix://' . $path, $errno, $errstr, 1.0);
+
+        if (!$resource) {
+            return Promise\reject(new RuntimeException('Unable to connect to unix domain socket "' . $path . '": ' . $errstr, $errno));
+        }
+
+        return Promise\resolve(new Stream($resource, $this->loop));
+    }
+}

tests/UnixConnectorTest.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace React\Tests\SocketClient;
+
+use React\SocketClient\UnixConnector;
+
+class UnixConnectorTest extends TestCase
+{
+    private $loop;
+    private $connector;
+
+    public function setUp()
+    {
+        $this->loop = $this->getMock('React\EventLoop\LoopInterface');
+        $this->connector = new UnixConnector($this->loop);
+    }
+
+    public function testInvalid()
+    {
+        $promise = $this->connector->create('google.com', 80);
+        $promise->then(null, $this->expectCallableOnce());
+    }
+
+    public function testValid()
+    {
+        // random unix domain socket path
+        $path = sys_get_temp_dir() . '/test' . uniqid() . '.sock';
+
+        // temporarily create unix domain socket server to connect to
+        $server = stream_socket_server('unix://' . $path, $errno, $errstr);
+
+        // skip test if we can not create a test server (Windows etc.)
+        if (!$server) {
+            $this->markTestSkipped('Unable to create socket "' . $path . '": ' . $errstr . '(' . $errno .')');
+            return;
+        }
+
+        // tests succeeds if we get notified of successful connection
+        $promise = $this->connector->create($path, 0);
+        $promise->then($this->expectCallableOnce());
+
+        // clean up server
+        fclose($server);
+        unlink($path);
+    }
+}