diff --git a/src/main/php/peer/BSDSocket.class.php b/src/main/php/peer/BSDSocket.class.php
index bb4347b..b944295 100755
--- a/src/main/php/peer/BSDSocket.class.php
+++ b/src/main/php/peer/BSDSocket.class.php
@@ -17,7 +17,8 @@ class BSDSocket extends Socket {
     $options  = [];
   
   protected 
-    $rq       = '';
+    $rq       = '',
+    $state    = 0;
 
   /** @return peer.Sockets */
   public function kind() { return Sockets::$BSD; }
@@ -50,7 +51,7 @@ public function localEndpoint() {
    * @throws  lang.IllegalStateException if socket is already connected
    */
   public function setDomain($domain) {
-    if ($this->isConnected()) {
+    if ($this->_sock) {
       throw new \lang\IllegalStateException('Cannot set domain on connected socket');
     }
     $this->domain= $domain;
@@ -72,7 +73,7 @@ public function getDomain() {
    * @throws  lang.IllegalStateException if socket is already connected
    */
   public function setType($type) {
-    if ($this->isConnected()) {
+    if ($this->_sock) {
       throw new \lang\IllegalStateException('Cannot set type on connected socket');
     }
     $this->type= $type;
@@ -95,7 +96,7 @@ public function getType() {
    * @throws  lang.IllegalStateException if socket is already connected
    */
   public function setProtocol($protocol) {
-    if ($this->isConnected()) {
+    if ($this->_sock) {
       throw new \lang\IllegalStateException('Cannot set protocol on connected socket');
     }
     $this->protocol= $protocol;
@@ -130,19 +131,43 @@ public function getLastError() {
   public function setOption($level, $name, $value) {
     $this->options[$level][$name]= $value;
 
-    if ($this->isConnected()) {
+    if ($this->_sock) {
       socket_set_option($this->_sock, $level, $name, $value);
     }
   }
-  
+
   /**
-   * Connect
+   * Returns whether a connection has been established
    *
-   * @param   float timeout default 2.0
-   * @return  bool success
-   * @throws  peer.ConnectException
+   * @return bool
+   */
+  public function isConnected() {
+    if (null === $this->_sock) return false;
+
+    // For asynchronously connected sockets, check whether we can get the
+    // peer name. Once we get one, we've successfully established a connection!
+    if (1 === $this->state) {
+      if (false === socket_getpeername($this->_sock, $_, $_)) {
+        \xp::gc(__FILE__, __LINE__ - 1);
+        return false;
+      }
+
+      socket_set_block($this->_sock);
+      $this->state= 2;
+    }
+
+    return true;
+  }
+
+  /**
+   * Establish a connection
+   *
+   * @param  float $timeout
+   * @param  int $flags
+   * @return bool
+   * @throws peer.ConnectException
    */
-  public function connect($timeout= 2.0) {
+  protected function establish($timeout, $flags) {
     static $domains= [
       AF_INET   => 'AF_INET',
       AF_INET6  => 'AF_INET6',
@@ -155,9 +180,7 @@ public function connect($timeout= 2.0) {
       SOCK_SEQPACKET  => 'SOCK_SEQPACKET',
       SOCK_RDM        => 'SOCK_RDM'
     ];
-    
-    if ($this->isConnected()) return true;    // Short-cuircuit this
-    
+
     // Create socket...
     if (!($this->_sock= socket_create($this->domain, $this->type, $this->protocol))) {
       $this->_sock= null;
@@ -185,22 +208,24 @@ public function connect($timeout= 2.0) {
     $this->setTimeout($timeout);
 
     // ...and connect it
+    $host= (string)$this->host;
     switch ($this->domain) {
       case AF_INET:
       case AF_INET6: {
-        $host= null;
-        if ($this->host instanceof \InetAddress) {
-          $host= $this->host->asString();
+        if ($flags & STREAM_CLIENT_ASYNC_CONNECT) {
+          socket_set_nonblock($this->_sock);
+          socket_connect($this->_sock, $host, $this->port);
+          $this->state= 1;
+          $r= null;
         } else {
-          // TBD: Refactor
-          $host= gethostbyname($this->host);
+          $r= socket_connect($this->_sock, $host, $this->port);
+          $this->state= 2;
         }
-        $r= socket_connect($this->_sock, $host, $this->port);
         break;
       }
       
       case AF_UNIX: {
-        $r= socket_connect($this->_sock, $this->host);
+        $r= socket_connect($this->_sock, $host);
         break;
       }
     }
@@ -210,6 +235,7 @@ public function connect($timeout= 2.0) {
 
     // Check return status
     if (false === $r) {
+      $this->state= 0;
       $this->_sock= null;
       $e= new ConnectException(sprintf(
         'Connect to %s:%d failed: %s',
@@ -222,7 +248,7 @@ public function connect($timeout= 2.0) {
     }
     return true;
   }
-  
+
   /**
    * Close socket
    *
@@ -234,6 +260,7 @@ public function close() {
     socket_close($this->_sock);
     $this->_sock= null;
     $this->_eof= false;
+    $this->state= 0;
     return true;
   }
   /**
diff --git a/src/main/php/peer/Socket.class.php b/src/main/php/peer/Socket.class.php
index cd48da3..058477c 100755
--- a/src/main/php/peer/Socket.class.php
+++ b/src/main/php/peer/Socket.class.php
@@ -10,12 +10,10 @@
  * @see      php://network
  */
 class Socket implements Channel, Value {
-  public
-    $_eof     = false,
-    $host     = '',
-    $port     = 0;
+  public $host, $port;
     
   public
+    $_eof     = false,
     $_sock    = null,
     $_prefix  = 'tcp://',
     $_timeout = 60;
@@ -101,7 +99,7 @@ protected function getSocketOption($wrapper, $option) {
    * any PHP error/warning is returned - but since there's no function like
    * flasterror() we must rely on this
    *
-   * @return  string error
+   * @return string
    */  
   public function getLastError() {
     return isset(\xp::$errors[__FILE__]) ? trim(key(end(\xp::$errors[__FILE__]))) : 'unknown error';
@@ -110,41 +108,51 @@ public function getLastError() {
   /**
    * Returns whether a connection has been established
    *
-   * @return  bool connected
+   * @return bool
    */
   public function isConnected() {
-    return null !== $this->_sock;
+    if (null === $this->_sock) return false;
+
+    // For asynchronously connected sockets, the only way we seem to be able to
+    // reliably determine connectivity is to look up the remote socket name.
+    // See https://github.com/reactphp/socket/blob/master/src/TcpConnector.php#L105
+    if ((stream_context_get_options($this->context)['socket']['flags'] ?? 0) & STREAM_CLIENT_ASYNC_CONNECT) {
+      if (false === stream_socket_get_name($this->_sock, true)) return false;
+    }
+    return true;
   }
 
   /**
-   * Clone method. Ensure reconnect
+   * Ensures reconnect on clone
    *
+   * @return void
    */
   public function __clone() {
-    if (!$this->isConnected()) return;
+    if (null === $this->_sock) return;
+
+    $options= stream_context_get_options($this->context)['socket'];
     $this->close();
-    $this->connect();
+    $this->establish($options['timeout'] ?? 2.0, $options['flags'] ?? STREAM_CLIENT_CONNECT);
   }
-  
+
   /**
-   * Connect
+   * Establish a connection
    *
-   * @param   float timeout default 2.0
-   * @see     php://fsockopen
-   * @return  bool success
-   * @throws  peer.ConnectException
+   * @see    https://github.com/xp-framework/networking/issues/2
+   * @see    php://stream_socket_client
+   * @param  float $timeout
+   * @param  int $flags
+   * @return bool success
+   * @throws peer.ConnectException
    */
-  public function connect($timeout= 2.0) {
-    if ($this->isConnected()) return true;
-
-    // Force IPv4 for localhost, see https://github.com/xp-framework/networking/issues/2
+  protected function establish($timeout, $flags) {
     $host= (string)$this->host;
     if (!$this->_sock= stream_socket_client(
       $this->_prefix.('localhost' === $host ? '127.0.0.1' : $host).':'.$this->port,
       $errno,
       $errstr,
       $timeout,
-      STREAM_CLIENT_CONNECT,
+      $flags,
       $this->context
     )) {
       $this->_sock= null;
@@ -160,15 +168,47 @@ public function connect($timeout= 2.0) {
       throw $e;
     }
 
+    // Remember connection attributes
+    stream_context_set_option($this->context, 'socket', 'timeout', $timeout);
+    stream_context_set_option($this->context, 'socket', 'flags', $flags);
+
     $s= (int)$this->_timeout;
     stream_set_timeout($this->_sock, $s, (int)(1000 * ($this->_timeout - $s)));
     return true;
   }
 
+  /**
+   * Open a connection asynchronously. Unlike `connect()`, returns immediately.
+   *
+   * @param  float $timeout default 2.0
+   * @return bool
+   * @throws peer.ConnectException
+   */
+  public function open($timeout= 2.0) {
+    return null === $this->_sock
+      ? $this->establish($timeout, STREAM_CLIENT_CONNECT | STREAM_CLIENT_ASYNC_CONNECT)
+      : true
+    ;
+  }
+
+  /**
+   * Open a connection. Waits for it to be completely established before returning.
+   *
+   * @param  float $timeout default 2.0
+   * @return bool
+   * @throws peer.ConnectException
+   */
+  public function connect($timeout= 2.0) {
+    return null === $this->_sock
+      ? $this->establish($timeout, STREAM_CLIENT_CONNECT)
+      : true
+    ;
+  }
+
   /**
    * Close socket
    *
-   * @return  bool success
+   * @return bool
    */
   public function close() {
     if (null === $this->_sock) return false;
diff --git a/src/main/php/peer/Sockets.class.php b/src/main/php/peer/Sockets.class.php
index d00ec4a..94cc871 100755
--- a/src/main/php/peer/Sockets.class.php
+++ b/src/main/php/peer/Sockets.class.php
@@ -51,7 +51,8 @@ static function __static() { }
 
       public function select0(&$r, &$w, &$e, $timeout= null) {
         if (null === $timeout) {
-          $tv_sec= $tv_usec= null;
+          $tv_sec= null;
+          $tv_usec= 0;
         } else {
           $tv_sec= (int)floor($timeout);
           $tv_usec= (int)(($timeout - $tv_sec)  * 1000000);
diff --git a/src/test/php/peer/unittest/sockets/AbstractSocketTest.class.php b/src/test/php/peer/unittest/sockets/AbstractSocketTest.class.php
index f05ffe5..889df0f 100755
--- a/src/test/php/peer/unittest/sockets/AbstractSocketTest.class.php
+++ b/src/test/php/peer/unittest/sockets/AbstractSocketTest.class.php
@@ -384,4 +384,27 @@ public function select_keyed_array() {
 
     $this->assertEquals(['fixture' => $this->fixture], $r);
   }
+
+  #[Test]
+  public function open_connection_asynchronously() {
+    $this->fixture->open();
+
+    $read= $write= $error= [$this->fixture];
+    $this->fixture->kind()->select($read, $write, $error);
+
+    $this->assertTrue($this->fixture->isConnected());
+  }
+
+  #[Test]
+  public function open_connection_to_unbound_port() {
+
+    // Use port 4 which is unassigned and thus VERY unlikely to be bound, see
+    // https://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers
+    $fixture= $this->newSocket(self::$bindAddress[0], 4);
+    $fixture->open();
+    $read= $write= $error= [$fixture];
+    $fixture->kind()->select($read, $write, $error);
+
+    $this->assertFalse($fixture->isConnected());
+  }
 }
\ No newline at end of file
diff --git a/src/test/php/peer/unittest/sockets/SocketTest.class.php b/src/test/php/peer/unittest/sockets/SocketTest.class.php
index 53bf689..90a955f 100755
--- a/src/test/php/peer/unittest/sockets/SocketTest.class.php
+++ b/src/test/php/peer/unittest/sockets/SocketTest.class.php
@@ -4,11 +4,6 @@
 use peer\unittest\StartServer;
 use unittest\actions\VerifyThat;
 
-/**
- * TestCase
- *
- * @see      xp://peer.Socket
- */
 #[Action(eval: 'new StartServer(TestingServer::class, "connected", "shutdown")')]
 class SocketTest extends AbstractSocketTest {