jfjoch_broker: Allow to query connected writers

image_pusher/CBORFilePusher.cpp

@@ -57,4 +57,8 @@ std::string CBORFilePusher::PrintSetup() const {
     std::filesystem::path currentPath = std::filesystem::current_path();
     return "CBORFilePusher: CBOR messages for debugging are written directly to file in base directory " + currentPath.string();
 
-}
+}
+
+size_t CBORFilePusher::GetConnectedWriters() const {
+    return 1;
+}