Add connection setting for blocking mode of socket (#135)

* Add connection setting for blocking mode of socket

* Add warning that blocking socket is potentially dangerous

Author: Namoshek

README.md

@@ -142,6 +142,15 @@ $connectionSettings = (new \PhpMqtt\Client\ConnectionSettings)
     // The password used for authentication when connecting to the broker.
     ->setPassword(null)
 
+    // Whether to use a blocking socket or not. By default, the socket is non-blocking,
+    // which is required when using subscriptions and/or {@see MqttClient::loop()}.
+    // In rare cases, it might be required to use a blocking socket though. One such example
+    // is when sending large messages (e.g. binaries) and the broker has a limited receive buffer.
+    // 
+    // Note: When using a blocking socket, the MQTT client can get stuck if the socket is broken
+    //       or when the broker does not consume the sent data fast enough. Use with caution.
+    ->useBlockingSocket(false)
+    
     // The connect timeout defines the maximum amount of seconds the client will try to establish
     // a socket connection with the broker. The value cannot be less than 1 second.
     ->setConnectTimeout(60)

src/ConnectionSettings.php

@@ -13,6 +13,7 @@ class ConnectionSettings
 {
     private ?string $username                          = null;
     private ?string $password                          = null;
+    private bool $useBlockingSocket                    = false;
     private int $connectTimeout                        = 60;
     private int $socketTimeout                         = 5;
     private int $resendTimeout                         = 10;
@@ -80,6 +81,35 @@ public function getPassword(): ?string
         return $this->password;
     }
 
+    /**
+     * Whether to use a blocking socket or not. By default, the socket is non-blocking,
+     * which is required when using subscriptions and/or {@see MqttClient::loop()}.
+     * In rare cases, it might be required to use a blocking socket though. One such example
+     * is when sending large messages (e.g. binaries) and the broker has a limited receive buffer.
+     *
+     * Note: When using a blocking socket, the MQTT client can get stuck if the socket is broken
+     *       or when the broker does not consume the sent data fast enough. Use with caution.
+     *
+     * @param bool $useBlockingSocket
+     * @return ConnectionSettings
+     */
+    public function useBlockingSocket(bool $useBlockingSocket): ConnectionSettings
+    {
+        $copy = clone $this;
+
+        $copy->useBlockingModeForSocket = $useBlockingSocket;
+
+        return $copy;
+    }
+
+    /**
+     * @return bool
+     */
+    public function shouldUseBlockingSocket(): bool
+    {
+        return $this->useBlockingSocket;
+    }
+
     /**
      * The connect timeout is the maximum amount of seconds the client will try to establish
      * a socket connection with the broker. The value cannot be less than 1 second.

src/MqttClient.php

@@ -290,7 +290,7 @@ protected function establishSocketConnection(): void
         }
 
         stream_set_timeout($socket, $this->settings->getSocketTimeout());
-        stream_set_blocking($socket, false);
+        stream_set_blocking($socket, $this->settings->shouldUseBlockingSocket());
 
         $this->logger->debug('Socket opened and ready to use.');
 

tests/Feature/PublishSubscribeTest.php

@@ -7,6 +7,7 @@
 
 namespace Tests\Feature;
 
+use PhpMqtt\Client\ConnectionSettings;
 use PhpMqtt\Client\MqttClient;
 use Tests\TestCase;
 
@@ -20,29 +21,40 @@ class PublishSubscribeTest extends TestCase
     public function publishSubscribeData(): array
     {
         return [
-            ['test/foo/bar/baz', 'test/foo/bar/baz', 'hello world', []],
-            ['test/foo/bar/+', 'test/foo/bar/baz', 'hello world', ['baz']],
-            ['test/foo/+/baz', 'test/foo/bar/baz', 'hello world', ['bar']],
-            ['test/foo/#', 'test/foo/bar/baz', 'hello world', ['bar/baz']],
-            ['test/foo/+/bar/#', 'test/foo/my/bar/baz', 'hello world', ['my', 'baz']],
-            ['test/foo/+/bar/#', 'test/foo/my/bar/baz/blub', 'hello world', ['my', 'baz/blub']],
-            ['test/foo/bar/baz', 'test/foo/bar/baz', random_bytes(2 * 1024 * 1024), []], // 2MB message
+            [false, 'test/foo/bar/baz', 'test/foo/bar/baz', 'hello world', []],
+            [false, 'test/foo/bar/+', 'test/foo/bar/baz', 'hello world', ['baz']],
+            [false, 'test/foo/+/baz', 'test/foo/bar/baz', 'hello world', ['bar']],
+            [false, 'test/foo/#', 'test/foo/bar/baz', 'hello world', ['bar/baz']],
+            [false, 'test/foo/+/bar/#', 'test/foo/my/bar/baz', 'hello world', ['my', 'baz']],
+            [false, 'test/foo/+/bar/#', 'test/foo/my/bar/baz/blub', 'hello world', ['my', 'baz/blub']],
+            [false, 'test/foo/bar/baz', 'test/foo/bar/baz', random_bytes(2 * 1024 * 1024), []], // 2MB message
+            [true, 'test/foo/bar/baz', 'test/foo/bar/baz', 'hello world', []],
+            [true, 'test/foo/bar/+', 'test/foo/bar/baz', 'hello world', ['baz']],
+            [true, 'test/foo/+/baz', 'test/foo/bar/baz', 'hello world', ['bar']],
+            [true, 'test/foo/#', 'test/foo/bar/baz', 'hello world', ['bar/baz']],
+            [true, 'test/foo/+/bar/#', 'test/foo/my/bar/baz', 'hello world', ['my', 'baz']],
+            [true, 'test/foo/+/bar/#', 'test/foo/my/bar/baz/blub', 'hello world', ['my', 'baz/blub']],
+            [true, 'test/foo/bar/baz', 'test/foo/bar/baz', random_bytes(2 * 1024 * 1024), []], // 2MB message
         ];
     }
 
     /**
      * @dataProvider publishSubscribeData
      */
     public function test_publishing_and_subscribing_using_quality_of_service_0_works_as_intended(
+        bool $useBlockingSocket,
         string $subscriptionTopicFilter,
         string $publishTopic,
         string $publishMessage,
         array $matchedTopicWildcards
     ): void
     {
         // We connect and subscribe to a topic using the first client.
+        $connectionSettings = (new ConnectionSettings())
+            ->useBlockingSocket($useBlockingSocket);
+
         $subscriber = new MqttClient($this->mqttBrokerHost, $this->mqttBrokerPort, 'subscriber');
-        $subscriber->connect(null, true);
+        $subscriber->connect($connectionSettings, true);
 
         $subscriber->subscribe(
             $subscriptionTopicFilter,
@@ -76,15 +88,19 @@ function (string $topic, string $message, bool $retained, array $wildcards) use
      * @dataProvider publishSubscribeData
      */
     public function test_publishing_and_subscribing_using_quality_of_service_1_works_as_intended(
+        bool $useBlockingSocket,
         string $subscriptionTopicFilter,
         string $publishTopic,
         string $publishMessage,
         array $matchedTopicWildcards
     ): void
     {
         // We connect and subscribe to a topic using the first client.
+        $connectionSettings = (new ConnectionSettings())
+            ->useBlockingSocket($useBlockingSocket);
+
         $subscriber = new MqttClient($this->mqttBrokerHost, $this->mqttBrokerPort, 'subscriber');
-        $subscriber->connect(null, true);
+        $subscriber->connect($connectionSettings, true);
 
         $subscriber->subscribe(
             $subscriptionTopicFilter,
@@ -118,15 +134,19 @@ function (string $topic, string $message, bool $retained, array $wildcards) use
      * @dataProvider publishSubscribeData
      */
     public function test_publishing_and_subscribing_using_quality_of_service_2_works_as_intended(
+        bool $useBlockingSocket,
         string $subscriptionTopicFilter,
         string $publishTopic,
         string $publishMessage,
         array $matchedTopicWildcards
     ): void
     {
         // We connect and subscribe to a topic using the first client.
+        $connectionSettings = (new ConnectionSettings())
+            ->useBlockingSocket($useBlockingSocket);
+
         $subscriber = new MqttClient($this->mqttBrokerHost, $this->mqttBrokerPort, 'subscriber');
-        $subscriber->connect(null, true);
+        $subscriber->connect($connectionSettings, true);
 
         $subscription = function (string $topic, string $message, bool $retained, array $wildcards) use ($subscriber, $subscriptionTopicFilter, $publishTopic, $publishMessage, $matchedTopicWildcards) {
             // By asserting something here, we will avoid a no-assertions-in-test warning, making the test pass.