diff --git a/src/Internal/functions.php b/src/Internal/functions.php
index b4a1c12..b0311d5 100644
--- a/src/Internal/functions.php
+++ b/src/Internal/functions.php
@@ -114,6 +114,7 @@ function setupTls($socket, array $options, ?Cancellation $cancellation): void
         $suspension = EventLoop::getSuspension();
 
         // Watcher is guaranteed to be created, because we throw above if cancellation has already been requested
+        /** @psalm-suppress PossiblyUndefinedVariable $callbackId is defined below. */
         $cancellationId = $cancellation->subscribe(static function ($e) use ($suspension, &$callbackId): void {
             EventLoop::cancel($callbackId);
 
diff --git a/src/ResourceServerSocket.php b/src/ResourceServerSocket.php
index ce096c5..20f60e0 100644
--- a/src/ResourceServerSocket.php
+++ b/src/ResourceServerSocket.php
@@ -19,14 +19,14 @@ final class ResourceServerSocket implements ServerSocket, ResourceStream
     /** @var resource|null Stream socket server resource. */
     private $socket;
 
-    private string $callbackId;
+    private readonly string $callbackId;
 
     private readonly SocketAddress $address;
 
     private ?Suspension $acceptor = null;
 
-    /** @var \Closure(CancelledException) */
-    private \Closure $cancel;
+    /** @var \Closure(CancelledException):void */
+    private readonly \Closure $cancel;
 
     private readonly \Closure $errorHandler;
 
@@ -59,11 +59,11 @@ public function __construct(
 
         $acceptor = &$this->acceptor;
         $this->callbackId = EventLoop::onReadable($this->socket, static function () use (&$acceptor): void {
-            $acceptor->resume(true);
+            $acceptor?->resume(true);
             $acceptor = null;
         });
 
-        $callbackId = &$this->callbackId;
+        $callbackId = $this->callbackId;
         $this->cancel = static function (CancelledException $exception) use (&$acceptor, $callbackId): void {
             EventLoop::disable($callbackId);
 
diff --git a/src/ResourceUdpSocket.php b/src/ResourceUdpSocket.php
index cb7b1ca..4189ac9 100644
--- a/src/ResourceUdpSocket.php
+++ b/src/ResourceUdpSocket.php
@@ -21,14 +21,14 @@ final class ResourceUdpSocket implements UdpSocket, ResourceStream
     /** @var resource|null UDP socket resource. */
     private $socket;
 
-    private string $callbackId;
+    private readonly string $callbackId;
 
-    private InternetAddress $address;
+    private readonly InternetAddress $address;
 
     private ?Suspension $reader = null;
 
-    /** @var \Closure(CancelledException) */
-    private \Closure $cancel;
+    /** @var \Closure(CancelledException):void */
+    private readonly \Closure $cancel;
 
     private int $limit;
 
@@ -98,7 +98,7 @@ public function __construct($socket, int $limit = self::DEFAULT_LIMIT)
             $reader = null;
         });
 
-        $callbackId = &$this->callbackId;
+        $callbackId = $this->callbackId;
         $this->cancel = static function (CancelledException $exception) use (&$reader, $callbackId): void {
             EventLoop::disable($callbackId);
 
@@ -168,9 +168,9 @@ public function send(InternetAddress $address, string $data): void
             throw new SocketException('The datagram socket is not writable');
         }
 
-        try {
-            \set_error_handler($errorHandler);
+        \set_error_handler($errorHandler);
 
+        try {
             $result = \stream_socket_sendto($this->socket, $data, 0, $address->toString());
             /** @psalm-suppress TypeDoesNotContainType */
             if ($result < 0 || $result === false) {
diff --git a/test/ResourceDatagramSocketTest.php b/test/ResourceUdpSocketTest.php
similarity index 99%
rename from test/ResourceDatagramSocketTest.php
rename to test/ResourceUdpSocketTest.php
index 237641d..a54d766 100644
--- a/test/ResourceDatagramSocketTest.php
+++ b/test/ResourceUdpSocketTest.php
@@ -11,7 +11,7 @@
 use function Amp\async;
 use function Amp\delay;
 
-class ResourceDatagramSocketTest extends AsyncTestCase
+class ResourceUdpSocketTest extends AsyncTestCase
 {
     public function testBindEndpointInvalidScheme(): void
     {