diff --git a/composer.json b/composer.json
index 5ff904e..e6d17e1 100644
--- a/composer.json
+++ b/composer.json
@@ -31,7 +31,7 @@
         "react/dns": "^1.13",
         "react/event-loop": "^1.2",
         "react/promise": "^3.2 || ^2.6 || ^1.2.1",
-        "react/stream": "^1.4"
+        "react/stream": "3.x-dev as 1.666.666"
     },
     "require-dev": {
         "phpunit/phpunit": "^9.6 || ^7.5",
diff --git a/src/Connection.php b/src/Connection.php
index 6bc8deb..7707e8e 100644
--- a/src/Connection.php
+++ b/src/Connection.php
@@ -78,42 +78,42 @@ public function __construct($resource, LoopInterface $loop)
         $this->input->on('close', [$this, 'close']);
     }
 
-    public function isReadable()
+    public function isReadable(): bool
     {
         return $this->input->isReadable();
     }
 
-    public function isWritable()
+    public function isWritable(): bool
     {
         return $this->input->isWritable();
     }
 
-    public function pause()
+    public function pause(): void
     {
         $this->input->pause();
     }
 
-    public function resume()
+    public function resume(): void
     {
         $this->input->resume();
     }
 
-    public function pipe(WritableStreamInterface $dest, array $options = [])
+    public function pipe(WritableStreamInterface $dest, array $options = []): WritableStreamInterface
     {
         return $this->input->pipe($dest, $options);
     }
 
-    public function write($data)
+    public function write($data): bool
     {
         return $this->input->write($data);
     }
 
-    public function end($data = null)
+    public function end($data = null): void
     {
         $this->input->end($data);
     }
 
-    public function close()
+    public function close(): void
     {
         $this->input->close();
         $this->handleClose();
@@ -132,7 +132,7 @@ public function handleClose()
         @\stream_socket_shutdown($this->stream, \STREAM_SHUT_RDWR);
     }
 
-    public function getRemoteAddress()
+    public function getRemoteAddress(): ?string
     {
         if (!\is_resource($this->stream)) {
             return null;
@@ -141,7 +141,7 @@ public function getRemoteAddress()
         return $this->parseAddress(\stream_socket_get_name($this->stream, true));
     }
 
-    public function getLocalAddress()
+    public function getLocalAddress(): ?string
     {
         if (!\is_resource($this->stream)) {
             return null;
@@ -150,7 +150,7 @@ public function getLocalAddress()
         return $this->parseAddress(\stream_socket_get_name($this->stream, false));
     }
 
-    private function parseAddress($address)
+    private function parseAddress($address): ?string
     {
         if ($address === false) {
             return null;
diff --git a/src/ConnectionInterface.php b/src/ConnectionInterface.php
index 64613b5..04e842e 100644
--- a/src/ConnectionInterface.php
+++ b/src/ConnectionInterface.php
@@ -82,7 +82,7 @@ interface ConnectionInterface extends DuplexStreamInterface
      *
      * @return ?string remote address (URI) or null if unknown
      */
-    public function getRemoteAddress();
+    public function getRemoteAddress(): ?string;
 
     /**
      * Returns the full local address (full URI with scheme, IP and port) where this connection has been established with
@@ -115,5 +115,5 @@ public function getRemoteAddress();
      * @return ?string local address (URI) or null if unknown
      * @see self::getRemoteAddress()
      */
-    public function getLocalAddress();
+    public function getLocalAddress(): ?string;
 }
diff --git a/src/Connector.php b/src/Connector.php
index 8a5e994..4c7b97a 100644
--- a/src/Connector.php
+++ b/src/Connector.php
@@ -6,6 +6,7 @@
 use React\Dns\Resolver\Factory as DnsFactory;
 use React\Dns\Resolver\ResolverInterface;
 use React\EventLoop\LoopInterface;
+use React\Promise\PromiseInterface;
 use function React\Promise\reject;
 
 /**
@@ -146,7 +147,7 @@ public function __construct(array $context = [], ?LoopInterface $loop = null)
         }
     }
 
-    public function connect($uri)
+    public function connect($uri): PromiseInterface
     {
         $scheme = 'tcp';
         if (\strpos($uri, '://') !== false) {
@@ -173,7 +174,7 @@ public function connect($uri)
      * @return string
      * @internal
      */
-    public static function uri(array $parts, $host, $ip)
+    public static function uri(array $parts, $host, $ip): string
     {
         $uri = '';
 
diff --git a/src/ConnectorInterface.php b/src/ConnectorInterface.php
index 1f07b75..687d43c 100644
--- a/src/ConnectorInterface.php
+++ b/src/ConnectorInterface.php
@@ -2,6 +2,8 @@
 
 namespace React\Socket;
 
+use React\Promise\PromiseInterface;
+
 /**
  * The `ConnectorInterface` is responsible for providing an interface for
  * establishing streaming connections, such as a normal TCP/IP connection.
@@ -55,5 +57,5 @@ interface ConnectorInterface
      *     Resolves with a `ConnectionInterface` on success or rejects with an `Exception` on error.
      * @see ConnectionInterface
      */
-    public function connect($uri);
+    public function connect($uri): PromiseInterface;
 }
diff --git a/src/DnsConnector.php b/src/DnsConnector.php
index 4a8d1a0..aa883ce 100644
--- a/src/DnsConnector.php
+++ b/src/DnsConnector.php
@@ -18,7 +18,7 @@ public function __construct(ConnectorInterface $connector, ResolverInterface $re
         $this->resolver = $resolver;
     }
 
-    public function connect($uri)
+    public function connect($uri): PromiseInterface
     {
         $original = $uri;
         if (\strpos($uri, '://') === false) {
diff --git a/src/FdServer.php b/src/FdServer.php
index b00681c..cada924 100644
--- a/src/FdServer.php
+++ b/src/FdServer.php
@@ -146,7 +146,7 @@ public function __construct($fd, ?LoopInterface $loop = null)
         $this->resume();
     }
 
-    public function getAddress()
+    public function getAddress(): ?string
     {
         if (!\is_resource($this->master)) {
             return null;
@@ -167,7 +167,7 @@ public function getAddress()
         return 'tcp://' . $address;
     }
 
-    public function pause()
+    public function pause(): void
     {
         if (!$this->listening) {
             return;
@@ -177,7 +177,7 @@ public function pause()
         $this->listening = false;
     }
 
-    public function resume()
+    public function resume(): void
     {
         if ($this->listening || !\is_resource($this->master)) {
             return;
@@ -195,7 +195,7 @@ public function resume()
         $this->listening = true;
     }
 
-    public function close()
+    public function close(): void
     {
         if (!\is_resource($this->master)) {
             return;
@@ -207,7 +207,7 @@ public function close()
     }
 
     /** @internal */
-    public function handleConnection($socket)
+    public function handleConnection($socket): void
     {
         $connection = new Connection($socket, $this->loop);
         $connection->unix = $this->unix;
diff --git a/src/FixedUriConnector.php b/src/FixedUriConnector.php
index f83241d..7d4f998 100644
--- a/src/FixedUriConnector.php
+++ b/src/FixedUriConnector.php
@@ -2,6 +2,8 @@
 
 namespace React\Socket;
 
+use React\Promise\PromiseInterface;
+
 /**
  * Decorates an existing Connector to always use a fixed, preconfigured URI
  *
@@ -34,7 +36,7 @@ public function __construct($uri, ConnectorInterface $connector)
         $this->connector = $connector;
     }
 
-    public function connect($_)
+    public function connect($_): PromiseInterface
     {
         return $this->connector->connect($this->uri);
     }
diff --git a/src/HappyEyeBallsConnectionBuilder.php b/src/HappyEyeBallsConnectionBuilder.php
index 57a94aa..beefd4f 100644
--- a/src/HappyEyeBallsConnectionBuilder.php
+++ b/src/HappyEyeBallsConnectionBuilder.php
@@ -54,7 +54,7 @@ final class HappyEyeBallsConnectionBuilder
     public $lastError6;
     public $lastError4;
 
-    public function __construct(LoopInterface $loop, ConnectorInterface $connector, ResolverInterface $resolver, $uri, $host, $parts)
+    public function __construct(LoopInterface $loop, ConnectorInterface $connector, ResolverInterface $resolver, string $uri, string $host, array $parts)
     {
         $this->loop = $loop;
         $this->connector = $connector;
@@ -64,7 +64,7 @@ public function __construct(LoopInterface $loop, ConnectorInterface $connector,
         $this->parts = $parts;
     }
 
-    public function connect()
+    public function connect(): PromiseInterface
     {
         return new Promise(function ($resolve, $reject) {
             $lookupResolve = function ($type) use ($resolve, $reject) {
@@ -123,7 +123,7 @@ public function connect()
      *     always resolves with a list of IP addresses on success or an empty
      *     list on error.
      */
-    public function resolve($type, $reject)
+    public function resolve(int $type, callable $reject): PromiseInterface
     {
         return $this->resolver->resolveAll($this->host, $type)->then(null, function (\Exception $e) use ($type, $reject) {
             unset($this->resolverPromises[$type]);
@@ -159,7 +159,7 @@ public function resolve($type, $reject)
     /**
      * @internal
      */
-    public function check($resolve, $reject)
+    public function check(callable $resolve, callable $reject)
     {
         $ip = \array_shift($this->connectQueue);
 
@@ -168,13 +168,13 @@ public function check($resolve, $reject)
         \end($this->connectionPromises);
         $index = \key($this->connectionPromises);
 
-        $this->connectionPromises[$index]->then(function ($connection) use ($index, $resolve) {
+        $this->connectionPromises[$index]->then(function ($connection) use ($index, $resolve): void {
             unset($this->connectionPromises[$index]);
 
             $this->cleanUp();
 
             $resolve($connection);
-        }, function (\Exception $e) use ($index, $ip, $resolve, $reject) {
+        }, function (\Exception $e) use ($index, $ip, $resolve, $reject): void {
             unset($this->connectionPromises[$index]);
 
             $this->failureCount++;
@@ -228,8 +228,9 @@ public function check($resolve, $reject)
 
     /**
      * @internal
+     * @return PromiseInterface<ConnectionInterface>
      */
-    public function attemptConnection($ip)
+    public function attemptConnection($ip): PromiseInterface
     {
         $uri = Connector::uri($this->parts, $this->host, $ip);
 
@@ -239,7 +240,7 @@ public function attemptConnection($ip)
     /**
      * @internal
      */
-    public function cleanUp()
+    public function cleanUp(): void
     {
         // clear list of outstanding IPs to avoid creating new connections
         $this->connectQueue = [];
@@ -267,7 +268,7 @@ public function cleanUp()
     /**
      * @internal
      */
-    public function hasBeenResolved()
+    public function hasBeenResolved(): bool
     {
         foreach ($this->resolved as $typeHasBeenResolved) {
             if ($typeHasBeenResolved === false) {
@@ -286,6 +287,8 @@ public function hasBeenResolved()
      * @link https://tools.ietf.org/html/rfc8305#section-4
      *
      * @internal
+     *
+     * @param array<string> $ips
      */
     public function mixIpsIntoConnectQueue(array $ips)
     {
@@ -307,7 +310,7 @@ public function mixIpsIntoConnectQueue(array $ips)
      * @internal
      * @return string
      */
-    public function error()
+    public function error(): string
     {
         if ($this->lastError4 === $this->lastError6) {
             $message = $this->lastError6;
diff --git a/src/HappyEyeBallsConnector.php b/src/HappyEyeBallsConnector.php
index 89ec203..777f6e7 100644
--- a/src/HappyEyeBallsConnector.php
+++ b/src/HappyEyeBallsConnector.php
@@ -5,6 +5,7 @@
 use React\Dns\Resolver\ResolverInterface;
 use React\EventLoop\Loop;
 use React\EventLoop\LoopInterface;
+use React\Promise\PromiseInterface;
 use function React\Promise\reject;
 
 final class HappyEyeBallsConnector implements ConnectorInterface
@@ -20,7 +21,7 @@ public function __construct(?LoopInterface $loop, ConnectorInterface $connector,
         $this->resolver = $resolver;
     }
 
-    public function connect($uri)
+    public function connect($uri): PromiseInterface
     {
         $original = $uri;
         if (\strpos($uri, '://') === false) {
diff --git a/src/LimitingServer.php b/src/LimitingServer.php
index 4742e25..de1922a 100644
--- a/src/LimitingServer.php
+++ b/src/LimitingServer.php
@@ -113,17 +113,17 @@ public function __construct(ServerInterface $server, $connectionLimit, $pauseOnL
      *
      * @return ConnectionInterface[]
      */
-    public function getConnections()
+    public function getConnections(): array
     {
         return $this->connections;
     }
 
-    public function getAddress()
+    public function getAddress(): ?string
     {
         return $this->server->getAddress();
     }
 
-    public function pause()
+    public function pause(): void
     {
         if (!$this->manuPaused) {
             $this->manuPaused = true;
@@ -134,7 +134,7 @@ public function pause()
         }
     }
 
-    public function resume()
+    public function resume(): void
     {
         if ($this->manuPaused) {
             $this->manuPaused = false;
@@ -145,13 +145,13 @@ public function resume()
         }
     }
 
-    public function close()
+    public function close(): void
     {
         $this->server->close();
     }
 
     /** @internal */
-    public function handleConnection(ConnectionInterface $connection)
+    public function handleConnection(ConnectionInterface $connection): void
     {
         // close connection if limit exceeded
         if ($this->limit !== null && \count($this->connections) >= $this->limit) {
@@ -178,7 +178,7 @@ public function handleConnection(ConnectionInterface $connection)
     }
 
     /** @internal */
-    public function handleDisconnection(ConnectionInterface $connection)
+    public function handleDisconnection(ConnectionInterface $connection): void
     {
         unset($this->connections[\array_search($connection, $this->connections)]);
 
@@ -193,7 +193,7 @@ public function handleDisconnection(ConnectionInterface $connection)
     }
 
     /** @internal */
-    public function handleError(\Exception $error)
+    public function handleError(\Exception $error): void
     {
         $this->emit('error', [$error]);
     }
diff --git a/src/SecureConnector.php b/src/SecureConnector.php
index 7626b0a..9574f1b 100644
--- a/src/SecureConnector.php
+++ b/src/SecureConnector.php
@@ -5,6 +5,7 @@
 use React\EventLoop\Loop;
 use React\EventLoop\LoopInterface;
 use React\Promise\Promise;
+use React\Promise\PromiseInterface;
 use function React\Promise\reject;
 
 final class SecureConnector implements ConnectorInterface
@@ -20,7 +21,7 @@ public function __construct(ConnectorInterface $connector, ?LoopInterface $loop
         $this->context = $context;
     }
 
-    public function connect($uri)
+    public function connect($uri): PromiseInterface
     {
         if (\strpos($uri, '://') === false) {
             $uri = 'tls://' . $uri;
diff --git a/src/SecureServer.php b/src/SecureServer.php
index 7ef5d94..04f7f0f 100644
--- a/src/SecureServer.php
+++ b/src/SecureServer.php
@@ -138,7 +138,7 @@ public function __construct(ServerInterface $tcp, ?LoopInterface $loop = null, a
         });
     }
 
-    public function getAddress()
+    public function getAddress(): ?string
     {
         $address = $this->tcp->getAddress();
         if ($address === null) {
@@ -148,23 +148,23 @@ public function getAddress()
         return \str_replace('tcp://' , 'tls://', $address);
     }
 
-    public function pause()
+    public function pause(): void
     {
         $this->tcp->pause();
     }
 
-    public function resume()
+    public function resume(): void
     {
         $this->tcp->resume();
     }
 
-    public function close()
+    public function close(): void
     {
-        return $this->tcp->close();
+        $this->tcp->close();
     }
 
     /** @internal */
-    public function handleConnection(ConnectionInterface $connection)
+    public function handleConnection(ConnectionInterface $connection): void
     {
         if (!$connection instanceof Connection) {
             $this->emit('error', [new \UnexpectedValueException('Base server does not use internal Connection class exposing stream resource')]);
diff --git a/src/ServerInterface.php b/src/ServerInterface.php
index aa79fa1..56511c2 100644
--- a/src/ServerInterface.php
+++ b/src/ServerInterface.php
@@ -75,7 +75,7 @@ interface ServerInterface extends EventEmitterInterface
      *
      * @return ?string the full listening address (URI) or NULL if it is unknown (not applicable to this server socket or already closed)
      */
-    public function getAddress();
+    public function getAddress(): ?string;
 
     /**
      * Pauses accepting new incoming connections.
@@ -114,7 +114,7 @@ public function getAddress();
      * @see self::resume()
      * @return void
      */
-    public function pause();
+    public function pause(): void;
 
     /**
      * Resumes accepting new incoming connections.
@@ -136,7 +136,7 @@ public function pause();
      * @see self::pause()
      * @return void
      */
-    public function resume();
+    public function resume(): void;
 
     /**
      * Shuts down this listening socket
@@ -147,5 +147,5 @@ public function resume();
      *
      * @return void
      */
-    public function close();
+    public function close(): void;
 }
diff --git a/src/SocketServer.php b/src/SocketServer.php
index 2106ff3..7d9720f 100644
--- a/src/SocketServer.php
+++ b/src/SocketServer.php
@@ -75,22 +75,22 @@ public function __construct($uri, array $context = [], ?LoopInterface $loop = nu
         });
     }
 
-    public function getAddress()
+    public function getAddress(): ?string
     {
         return $this->server->getAddress();
     }
 
-    public function pause()
+    public function pause(): void
     {
         $this->server->pause();
     }
 
-    public function resume()
+    public function resume(): void
     {
         $this->server->resume();
     }
 
-    public function close()
+    public function close(): void
     {
         $this->server->close();
     }
@@ -144,7 +144,7 @@ public static function accept($socket)
      * @copyright Copyright (c) 2023 Christian Lück, taken from https://github.com/clue/errno with permission
      * @codeCoverageIgnore
      */
-    public static function errno($errstr)
+    public static function errno($errstr): int
     {
         // PHP defines the required `strerror()` function through either `ext-sockets`, `ext-posix` or `ext-pcntl`
         $strerror = \function_exists('socket_strerror') ? 'socket_strerror' : (\function_exists('posix_strerror') ? 'posix_strerror' : (\function_exists('pcntl_strerror') ? 'pcntl_strerror' : null));
@@ -193,7 +193,7 @@ public static function errno($errstr)
      * @copyright Copyright (c) 2023 Christian Lück, taken from https://github.com/clue/errno with permission
      * @codeCoverageIgnore
      */
-    public static function errconst($errno)
+    public static function errconst($errno): string
     {
         // PHP defines most useful errno constants like `ECONNREFUSED` through constants in `ext-sockets` like `SOCKET_ECONNREFUSED`
         // PHP also defines a hand full of errno constants like `EMFILE` through constants in `ext-pcntl` like `PCNTL_EMFILE`
diff --git a/src/StreamEncryption.php b/src/StreamEncryption.php
index b03b79b..e3d3c79 100644
--- a/src/StreamEncryption.php
+++ b/src/StreamEncryption.php
@@ -4,6 +4,7 @@
 
 use React\EventLoop\LoopInterface;
 use React\Promise\Deferred;
+use React\Promise\PromiseInterface;
 
 /**
  * This class is considered internal and its API should not be relied upon
@@ -45,7 +46,7 @@ public function __construct(LoopInterface $loop, $server = true)
      * @param Connection $stream
      * @return \React\Promise\PromiseInterface<Connection>
      */
-    public function enable(Connection $stream)
+    public function enable(Connection $stream): PromiseInterface
     {
         return $this->toggle($stream, true);
     }
@@ -55,7 +56,7 @@ public function enable(Connection $stream)
      * @param bool $toggle
      * @return \React\Promise\PromiseInterface<Connection>
      */
-    public function toggle(Connection $stream, $toggle)
+    public function toggle(Connection $stream, bool $toggle): PromiseInterface
     {
         // pause actual stream instance to continue operation on raw stream socket
         $stream->pause();
@@ -106,10 +107,10 @@ public function toggle(Connection $stream, $toggle)
      * @param int $method
      * @return void
      */
-    public function toggleCrypto($socket, Deferred $deferred, $toggle, $method)
+    public function toggleCrypto($socket, Deferred $deferred, $toggle, $method): void
     {
         $error = null;
-        \set_error_handler(function ($_, $errstr) use (&$error) {
+        \set_error_handler(function ($_, string $errstr) use (&$error) {
             $error = \str_replace(["\r", "\n"], ' ', $errstr);
 
             // remove useless function name from error message
diff --git a/src/TcpConnector.php b/src/TcpConnector.php
index 0949184..59f4e26 100644
--- a/src/TcpConnector.php
+++ b/src/TcpConnector.php
@@ -5,6 +5,7 @@
 use React\EventLoop\Loop;
 use React\EventLoop\LoopInterface;
 use React\Promise\Promise;
+use React\Promise\PromiseInterface;
 use function React\Promise\reject;
 
 final class TcpConnector implements ConnectorInterface
@@ -18,7 +19,7 @@ public function __construct(?LoopInterface $loop = null, array $context = [])
         $this->context = $context;
     }
 
-    public function connect($uri)
+    public function connect($uri): PromiseInterface
     {
         if (\strpos($uri, '://') === false) {
             $uri = 'tcp://' . $uri;
diff --git a/src/TcpServer.php b/src/TcpServer.php
index a49ca9d..a7c91c0 100644
--- a/src/TcpServer.php
+++ b/src/TcpServer.php
@@ -189,7 +189,7 @@ public function __construct($uri, ?LoopInterface $loop = null, array $context =
         $this->resume();
     }
 
-    public function getAddress()
+    public function getAddress(): ?string
     {
         if (!\is_resource($this->master)) {
             return null;
@@ -206,7 +206,7 @@ public function getAddress()
         return 'tcp://' . $address;
     }
 
-    public function pause()
+    public function pause(): void
     {
         if (!$this->listening) {
             return;
@@ -216,7 +216,7 @@ public function pause()
         $this->listening = false;
     }
 
-    public function resume()
+    public function resume(): void
     {
         if ($this->listening || !\is_resource($this->master)) {
             return;
@@ -234,7 +234,7 @@ public function resume()
         $this->listening = true;
     }
 
-    public function close()
+    public function close(): void
     {
         if (!\is_resource($this->master)) {
             return;
@@ -246,7 +246,7 @@ public function close()
     }
 
     /** @internal */
-    public function handleConnection($socket)
+    public function handleConnection($socket): void
     {
         $this->emit('connection', [
             new Connection($socket, $this->loop)
diff --git a/src/TimeoutConnector.php b/src/TimeoutConnector.php
index 5031a0b..4ee2c55 100644
--- a/src/TimeoutConnector.php
+++ b/src/TimeoutConnector.php
@@ -5,6 +5,7 @@
 use React\EventLoop\Loop;
 use React\EventLoop\LoopInterface;
 use React\Promise\Promise;
+use React\Promise\PromiseInterface;
 
 final class TimeoutConnector implements ConnectorInterface
 {
@@ -19,7 +20,7 @@ public function __construct(ConnectorInterface $connector, $timeout, ?LoopInterf
         $this->loop = $loop ?? Loop::get();
     }
 
-    public function connect($uri)
+    public function connect($uri): PromiseInterface
     {
         $promise = $this->connector->connect($uri);
 
diff --git a/src/UnixConnector.php b/src/UnixConnector.php
index ecc6262..4fec34e 100644
--- a/src/UnixConnector.php
+++ b/src/UnixConnector.php
@@ -4,6 +4,7 @@
 
 use React\EventLoop\Loop;
 use React\EventLoop\LoopInterface;
+use React\Promise\PromiseInterface;
 use function React\Promise\reject;
 use function React\Promise\resolve;
 
@@ -22,7 +23,7 @@ public function __construct(?LoopInterface $loop = null)
         $this->loop = $loop ?? Loop::get();
     }
 
-    public function connect($path)
+    public function connect($path): PromiseInterface
     {
         if (\strpos($path, '://') === false) {
             $path = 'unix://' . $path;
diff --git a/src/UnixServer.php b/src/UnixServer.php
index 8b4e416..ce2d054 100644
--- a/src/UnixServer.php
+++ b/src/UnixServer.php
@@ -93,7 +93,7 @@ public function __construct($path, ?LoopInterface $loop = null, array $context =
         $this->resume();
     }
 
-    public function getAddress()
+    public function getAddress(): ?string
     {
         if (!\is_resource($this->master)) {
             return null;
@@ -102,7 +102,7 @@ public function getAddress()
         return 'unix://' . \stream_socket_get_name($this->master, false);
     }
 
-    public function pause()
+    public function pause(): void
     {
         if (!$this->listening) {
             return;
@@ -112,7 +112,7 @@ public function pause()
         $this->listening = false;
     }
 
-    public function resume()
+    public function resume(): void
     {
         if ($this->listening || !is_resource($this->master)) {
             return;
@@ -130,7 +130,7 @@ public function resume()
         $this->listening = true;
     }
 
-    public function close()
+    public function close(): void
     {
         if (!\is_resource($this->master)) {
             return;
@@ -142,7 +142,7 @@ public function close()
     }
 
     /** @internal */
-    public function handleConnection($socket)
+    public function handleConnection($socket): void
     {
         $connection = new Connection($socket, $this->loop);
         $connection->unix = true;