[Server] Support server notifications

composer.json

@@ -23,7 +23,6 @@
         "opis/json-schema": "^2.4",
         "phpdocumentor/reflection-docblock": "^5.6",
         "psr/container": "^2.0",
-        "psr/event-dispatcher": "^1.0",
         "psr/log": "^1.0 || ^2.0 || ^3.0",
         "symfony/finder": "^6.4 || ^7.3",
         "symfony/uid": "^6.4 || ^7.3"

examples/09-standalone-cli/index.php

@@ -27,8 +27,10 @@
     $logger
 );
 
+$notificationPublisher = new Mcp\Server\NotificationPublisher();
+
 // Set up the server
-$sever = new Mcp\Server($jsonRpcHandler, $logger);
+$sever = new Mcp\Server($jsonRpcHandler, $notificationPublisher, $logger);
 
 // Create the transport layer using Stdio
 $transport = new Mcp\Server\Transport\StdioTransport(logger: $logger);

src/Capability/Registry.php

@@ -17,16 +17,15 @@
 use Mcp\Capability\Registry\ResourceReference;
 use Mcp\Capability\Registry\ResourceTemplateReference;
 use Mcp\Capability\Registry\ToolReference;
-use Mcp\Event\PromptListChangedEvent;
-use Mcp\Event\ResourceListChangedEvent;
-use Mcp\Event\ResourceTemplateListChangedEvent;
-use Mcp\Event\ToolListChangedEvent;
+use Mcp\Schema\Notification\PromptListChangedNotification;
+use Mcp\Schema\Notification\ResourceListChangedNotification;
+use Mcp\Schema\Notification\ToolListChangedNotification;
 use Mcp\Schema\Prompt;
 use Mcp\Schema\Resource;
 use Mcp\Schema\ResourceTemplate;
 use Mcp\Schema\ServerCapabilities;
 use Mcp\Schema\Tool;
-use Psr\EventDispatcher\EventDispatcherInterface;
+use Mcp\Server\NotificationPublisher;
 use Psr\Log\LoggerInterface;
 use Psr\Log\NullLogger;
 
@@ -61,7 +60,7 @@ final class Registry implements ReferenceProviderInterface, ReferenceRegistryInt
     private array $resourceTemplates = [];
 
     public function __construct(
-        private readonly ?EventDispatcherInterface $eventDispatcher = null,
+        private readonly NotificationPublisher $notificationPublisher = new NotificationPublisher(),
         private readonly LoggerInterface $logger = new NullLogger(),
     ) {
     }
@@ -74,12 +73,12 @@ public function getCapabilities(): ServerCapabilities
 
         return new ServerCapabilities(
             tools: [] !== $this->tools,
-            toolsListChanged: $this->eventDispatcher instanceof EventDispatcherInterface,
+            toolsListChanged: true,
             resources: [] !== $this->resources || [] !== $this->resourceTemplates,
             resourcesSubscribe: false,
-            resourcesListChanged: $this->eventDispatcher instanceof EventDispatcherInterface,
+            resourcesListChanged: true,
             prompts: [] !== $this->prompts,
-            promptsListChanged: $this->eventDispatcher instanceof EventDispatcherInterface,
+            promptsListChanged: true,
             logging: false,
             completions: true,
         );
@@ -100,7 +99,7 @@ public function registerTool(Tool $tool, callable|array|string $handler, bool $i
 
         $this->tools[$toolName] = new ToolReference($tool, $handler, $isManual);
 
-        $this->eventDispatcher?->dispatch(new ToolListChangedEvent());
+        $this->notificationPublisher->enqueue(new ToolListChangedNotification());
     }
 
     public function registerResource(Resource $resource, callable|array|string $handler, bool $isManual = false): void
@@ -118,7 +117,7 @@ public function registerResource(Resource $resource, callable|array|string $hand
 
         $this->resources[$uri] = new ResourceReference($resource, $handler, $isManual);
 
-        $this->eventDispatcher?->dispatch(new ResourceListChangedEvent());
+        $this->notificationPublisher->enqueue(new ResourceListChangedNotification());
     }
 
     public function registerResourceTemplate(
@@ -145,7 +144,8 @@ public function registerResourceTemplate(
             $completionProviders,
         );
 
-        $this->eventDispatcher?->dispatch(new ResourceTemplateListChangedEvent());
+        // TODO: Create ResourceTemplateListChangedNotification.
+        // $this->notificationPublisher->enqueue(ResourceTemplateListChangedNotification::class);
     }
 
     public function registerPrompt(
@@ -167,7 +167,7 @@ public function registerPrompt(
 
         $this->prompts[$promptName] = new PromptReference($prompt, $handler, $isManual, $completionProviders);
 
-        $this->eventDispatcher?->dispatch(new PromptListChangedEvent());
+        $this->notificationPublisher->enqueue(new PromptListChangedNotification());
     }
 
     public function clear(): void

src/JsonRpc/MessageFactory.php

@@ -18,6 +18,10 @@
 use Mcp\Schema\Request;
 
 /**
+ * @phpstan-type RequestData array{
+ *      params?: array<string, mixed>,
+ *  }
+ *
  * @author Christopher Hertel <[email protected]>
  */
 final class MessageFactory

src/Server.php

@@ -12,6 +12,7 @@
 namespace Mcp;
 
 use Mcp\JsonRpc\Handler;
+use Mcp\Server\NotificationPublisher;
 use Mcp\Server\ServerBuilder;
 use Mcp\Server\TransportInterface;
 use Psr\Log\LoggerInterface;
@@ -24,6 +25,7 @@ final class Server
 {
     public function __construct(
         private readonly Handler $jsonRpcHandler,
+        private readonly NotificationPublisher $notificationPublisher,
         private readonly LoggerInterface $logger = new NullLogger(),
     ) {
     }
@@ -63,6 +65,18 @@ public function connect(TransportInterface $transport): void
                 }
             }
 
+            foreach ($this->notificationPublisher->flush() as $notification) {
+                try {
+                    $transport->send(json_encode($notification, \JSON_THROW_ON_ERROR));
+                } catch (\JsonException $e) {
+                    $this->logger->error('Failed to encode notification to JSON.', [
+                        'notification' => $notification::class,
+                        'exception' => $e,
+                    ]);
+                    continue;
+                }
+            }
+
             usleep(1000);
         }
 

src/Server/NotificationPublisher.php

@@ -0,0 +1,40 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the official PHP MCP SDK.
+ *
+ * A collaboration between Symfony and the PHP Foundation.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Mcp\Server;
+
+use Mcp\Schema\JsonRpc\Notification;
+
+/**
+ * @author Aggelos Bellos <[email protected]>
+ */
+class NotificationPublisher
+{
+    /** @var list<Notification> */
+    private array $queue = [];
+
+    public function enqueue(Notification $notification): void
+    {
+        $this->queue[] = $notification;
+    }
+
+    /**
+     * @return \Generator<int, Notification, void, void>
+     */
+    public function flush(): iterable
+    {
+        yield from $this->queue;
+
+        $this->queue = [];
+    }
+}

src/Server/ServerBuilder.php

@@ -39,7 +39,6 @@
 use Mcp\Schema\ToolAnnotations;
 use Mcp\Server;
 use Psr\Container\ContainerInterface;
-use Psr\EventDispatcher\EventDispatcherInterface;
 use Psr\Log\LoggerInterface;
 use Psr\Log\NullLogger;
 use Psr\SimpleCache\CacheInterface;
@@ -61,8 +60,6 @@ final class ServerBuilder
 
     private ?PromptGetterInterface $promptGetter = null;
 
-    private ?EventDispatcherInterface $eventDispatcher = null;
-
     private ?ContainerInterface $container = null;
 
     private ?int $paginationLimit = 50;
@@ -154,13 +151,6 @@ public function setLogger(LoggerInterface $logger): self
         return $this;
     }
 
-    public function setEventDispatcher(EventDispatcherInterface $eventDispatcher): self
-    {
-        $this->eventDispatcher = $eventDispatcher;
-
-        return $this;
-    }
-
     public function setToolCaller(ToolCallerInterface $toolCaller): self
     {
         $this->toolCaller = $toolCaller;
@@ -276,9 +266,9 @@ public function addPrompt(callable|array|string $handler, ?string $name = null,
     public function build(): Server
     {
         $logger = $this->logger ?? new NullLogger();
-
+        $notificationPublisher = new NotificationPublisher();
         $container = $this->container ?? new Container();
-        $registry = new Registry($this->eventDispatcher, $logger);
+        $registry = new Registry($notificationPublisher, $logger);
 
         $referenceHandler = new ReferenceHandler($container);
         $toolCaller = $this->toolCaller ??= new ToolCaller($registry, $referenceHandler, $logger);
@@ -302,6 +292,7 @@ public function build(): Server
                 promptGetter: $promptGetter,
                 logger: $logger,
             ),
+            notificationPublisher: $notificationPublisher,
             logger: $logger,
         );
     }