Add handlers for control messages and callbacks

src/plugin/bridges/vst3.cpp

@@ -37,4 +37,9 @@ Vst3PluginBridge::Vst3PluginBridge()
     // This will block until all sockets have been connected to by the Wine VST
     // host
     connect_sockets_guarded();
+
+    host_callback_handler = std::jthread([&]() {
+        // TODO: Handle callbacks
+        // sockets.vst_host_callback.receive_multi();
+    });
 }

src/plugin/bridges/vst3.h

@@ -52,6 +52,12 @@ class Vst3PluginBridge : PluginBridge<Vst3Sockets<std::jthread>> {
     Vst3PluginBridge();
 
    private:
+    /**
+     * Handles callbacks from the plugin to the host over the
+     * `vst_host_callback` sockets.
+     */
+    std::jthread host_callback_handler;
+
     /**
      * The logging facility used for this instance of yabridge. Wraps around
      * `PluginBridge::generic_logger`.