Fix: use blocking socket only during publishing if configured (#141)

README.md

@@ -142,13 +142,11 @@ $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.
+    // Whether to use a blocking socket when publishing messages or not.
+    // Normally, this setting can be ignored. When publishing large messages with multiple kilobytes in size,
+    // a blocking socket may be required if the receipt buffer of the broker is not large enough.
+    //
+    // Note: This setting has no effect on subscriptions, only on the publishing of messages.
     ->useBlockingSocket(false)
 
     // The connect timeout defines the maximum amount of seconds the client will try to establish

src/ConnectionSettings.php

@@ -82,13 +82,11 @@ public function getPassword(): ?string
     }
 
     /**
-     * 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.
+     * Whether to use a blocking socket when publishing messages or not.
+     * Normally, this setting can be ignored. When publishing large messages with multiple kilobytes in size,
+     * a blocking socket may be required if the receipt buffer of the broker is not large enough.
      *
-     * 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.
+     * Note: This setting has no effect on subscriptions, only on the publishing of messages.
      *
      * @param bool $useBlockingSocket
      * @return ConnectionSettings
@@ -97,7 +95,7 @@ public function useBlockingSocket(bool $useBlockingSocket): ConnectionSettings
     {
         $copy = clone $this;
 
-        $copy->useBlockingModeForSocket = $useBlockingSocket;
+        $copy->useBlockingSocket = $useBlockingSocket;
 
         return $copy;
     }

src/MqttClient.php

@@ -290,7 +290,7 @@ protected function establishSocketConnection(): void
         }
 
         stream_set_timeout($socket, $this->settings->getSocketTimeout());
-        stream_set_blocking($socket, $this->settings->shouldUseBlockingSocket());
+        stream_set_blocking($socket, false);
 
         $this->logger->debug('Socket opened and ready to use.');
 
@@ -1140,8 +1140,16 @@ protected function writeToSocket(string $data, int $length = null): void
         $calculatedLength = strlen($data);
         $length           = min($length ?? $calculatedLength, $calculatedLength);
 
+        if ($this->settings->shouldUseBlockingSocket()) {
+            socket_set_blocking($this->socket, true);
+        }
+
         $result = @fwrite($this->socket, $data, $length);
 
+        if ($this->settings->shouldUseBlockingSocket()) {
+            socket_set_blocking($this->socket, false);
+        }
+
         if ($result === false || $result !== $length) {
             $this->logger->error('Sending data over the socket to the broker failed.');
             throw new DataTransferException(