diff --git a/client/client_connection.cpp b/client/client_connection.cpp
index 264875de..c3903dc2 100644
--- a/client/client_connection.cpp
+++ b/client/client_connection.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,11 +16,16 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+// prototype/interface header file
 #include "client_connection.hpp"
+
+// local headers
 #include "common/aixlog.hpp"
 #include "common/snap_exception.hpp"
 #include "common/str_compat.hpp"
 #include "message/hello.hpp"
+
+// standard headers
 #include <iostream>
 #include <mutex>
 
diff --git a/client/client_connection.hpp b/client/client_connection.hpp
index c67ad8ea..c9a527bc 100644
--- a/client/client_connection.hpp
+++ b/client/client_connection.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,16 +16,20 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef CLIENT_CONNECTION_H
-#define CLIENT_CONNECTION_H
+#ifndef CLIENT_CONNECTION_HPP
+#define CLIENT_CONNECTION_HPP
 
+// local headers
 #include "client_settings.hpp"
 #include "common/time_defs.hpp"
 #include "message/factory.hpp"
 #include "message/message.hpp"
 
-#include <atomic>
+// 3rd party headers
 #include <boost/asio.hpp>
+
+// standard headers
+#include <atomic>
 #include <condition_variable>
 #include <deque>
 #include <memory>
diff --git a/client/controller.cpp b/client/controller.cpp
index 96d01336..c252c0bd 100644
--- a/client/controller.cpp
+++ b/client/controller.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -20,7 +20,10 @@
 #define NOMINMAX
 #endif // NOMINMAX
 
+// prototype/interface header file
 #include "controller.hpp"
+
+// local headers
 #include "decoder/pcm_decoder.hpp"
 #if defined(HAS_OGG) && (defined(HAS_TREMOR) || defined(HAS_VORBIS))
 #include "decoder/ogg_decoder.hpp"
@@ -60,6 +63,7 @@
 #include "message/time.hpp"
 #include "time_provider.hpp"
 
+// standard headers
 #include <algorithm>
 #include <iostream>
 #include <memory>
diff --git a/client/player/alsa_player.cpp b/client/player/alsa_player.cpp
index f128ee1f..1187eda7 100644
--- a/client/player/alsa_player.cpp
+++ b/client/player/alsa_player.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,13 +16,20 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+// prototype/interface header file
 #include "alsa_player.hpp"
+
+// local headers
 #include "common/aixlog.hpp"
 #include "common/snap_exception.hpp"
 #include "common/str_compat.hpp"
 #include "common/utils/logging.hpp"
 #include "common/utils/string_utils.hpp"
 
+// 3rd party headers
+
+// standard headers
+
 using namespace std::chrono_literals;
 using namespace std;
 
diff --git a/client/player/alsa_player.hpp b/client/player/alsa_player.hpp
index 6d9ec21f..fefc2354 100644
--- a/client/player/alsa_player.hpp
+++ b/client/player/alsa_player.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -19,9 +19,13 @@
 #ifndef ALSA_PLAYER_HPP
 #define ALSA_PLAYER_HPP
 
+// local headers
 #include "player.hpp"
 
+// 3rd party headers
 #include <alsa/asoundlib.h>
+
+// standard headers
 #include <chrono>
 #include <optional>
 
diff --git a/client/player/coreaudio_player.hpp b/client/player/coreaudio_player.hpp
index f42f1c5a..d042e5b2 100644
--- a/client/player/coreaudio_player.hpp
+++ b/client/player/coreaudio_player.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -19,11 +19,14 @@
 #ifndef CORE_AUDIO_PLAYER_HPP
 #define CORE_AUDIO_PLAYER_HPP
 
+// local headers
+#include "player.hpp"
+
+// 3rd party headers
 #include <AudioToolbox/AudioQueue.h>
 #include <CoreAudio/CoreAudioTypes.h>
 #include <CoreFoundation/CFRunLoop.h>
 
-#include "player.hpp"
 
 namespace player
 {
diff --git a/client/player/file_player.cpp b/client/player/file_player.cpp
index 78d42cb7..09f9a190 100644
--- a/client/player/file_player.cpp
+++ b/client/player/file_player.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,14 +16,20 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#include <cassert>
-#include <iostream>
+// prototype/interface header file
+#include "file_player.hpp"
 
+// local headers
 #include "common/aixlog.hpp"
 #include "common/snap_exception.hpp"
 #include "common/str_compat.hpp"
 #include "common/utils/string_utils.hpp"
-#include "file_player.hpp"
+
+// 3rd party headers
+
+// standard headers
+#include <cassert>
+#include <iostream>
 
 using namespace std;
 
diff --git a/client/player/file_player.hpp b/client/player/file_player.hpp
index d26eacd5..e8599eef 100644
--- a/client/player/file_player.hpp
+++ b/client/player/file_player.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -19,7 +19,12 @@
 #ifndef FILE_PLAYER_HPP
 #define FILE_PLAYER_HPP
 
+// local headers
 #include "player.hpp"
+
+// 3rd party headers
+
+// standard headers
 #include <cstdio>
 #include <memory>
 
diff --git a/client/player/oboe_player.cpp b/client/player/oboe_player.cpp
index dff57d1d..a92ce0d4 100644
--- a/client/player/oboe_player.cpp
+++ b/client/player/oboe_player.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,13 +16,20 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#include <assert.h>
-#include <iostream>
+// prototype/interface header file
+#include "oboe_player.hpp"
 
+// local headers
 #include "common/aixlog.hpp"
 #include "common/snap_exception.hpp"
 #include "common/str_compat.hpp"
-#include "oboe_player.hpp"
+
+// 3rd party headers
+
+// standard headers
+#include <cassert>
+#include <iostream>
+
 
 using namespace std;
 
diff --git a/client/player/oboe_player.hpp b/client/player/oboe_player.hpp
index 22bb407d..10b0e659 100644
--- a/client/player/oboe_player.hpp
+++ b/client/player/oboe_player.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -19,10 +19,15 @@
 #ifndef OBOE_PLAYER_HPP
 #define OBOE_PLAYER_HPP
 
+// local headers
+#include "player.hpp"
+
+// 3rd party headers
 #include <oboe/LatencyTuner.h>
 #include <oboe/Oboe.h>
 
-#include "player.hpp"
+// standard headers
+
 
 namespace player
 {
diff --git a/client/player/opensl_player.cpp b/client/player/opensl_player.cpp
index 1fe652de..48995322 100644
--- a/client/player/opensl_player.cpp
+++ b/client/player/opensl_player.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,13 +16,20 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#include <assert.h>
-#include <iostream>
+// prototype/interface header file
+#include "opensl_player.hpp"
 
+// local headers
 #include "common/aixlog.hpp"
 #include "common/snap_exception.hpp"
 #include "common/str_compat.hpp"
-#include "opensl_player.hpp"
+
+// 3rd party headers
+
+// standard headers
+#include <cassert>
+#include <iostream>
+
 
 using namespace std;
 
diff --git a/client/player/opensl_player.hpp b/client/player/opensl_player.hpp
index 8854a83a..df39196a 100644
--- a/client/player/opensl_player.hpp
+++ b/client/player/opensl_player.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -19,11 +19,16 @@
 #ifndef OPEN_SL_PLAYER_HPP
 #define OPEN_SL_PLAYER_HPP
 
+// local headers
+#include "player.hpp"
+
+// 3rd party headers
 #include <SLES/OpenSLES.h>
 #include <SLES/OpenSLES_Android.h>
+
+// standard headers
 #include <string>
 
-#include "player.hpp"
 
 namespace player
 {
diff --git a/client/player/player.cpp b/client/player/player.cpp
index 863aed55..ebc78eaa 100644
--- a/client/player/player.cpp
+++ b/client/player/player.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,9 +16,16 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#include <cmath>
-#include <iostream>
+// prototype/interface header file
+#include "player.hpp"
 
+// local headers
+#include "common/aixlog.hpp"
+#include "common/snap_exception.hpp"
+#include "common/str_compat.hpp"
+#include "common/utils/string_utils.hpp"
+
+// 3rd party headers
 #ifdef WINDOWS
 #include <cstdlib>
 #else
@@ -35,11 +42,9 @@
 #pragma GCC diagnostic pop
 #endif
 
-#include "common/aixlog.hpp"
-#include "common/snap_exception.hpp"
-#include "common/str_compat.hpp"
-#include "common/utils/string_utils.hpp"
-#include "player.hpp"
+// standard headers
+#include <cmath>
+#include <iostream>
 
 
 using namespace std;
diff --git a/client/player/player.hpp b/client/player/player.hpp
index 4796c419..7226d99f 100644
--- a/client/player/player.hpp
+++ b/client/player/player.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -19,13 +19,16 @@
 #ifndef PLAYER_HPP
 #define PLAYER_HPP
 
+// local headers
 #include "client_settings.hpp"
 #include "common/aixlog.hpp"
 #include "common/endian.hpp"
 #include "stream.hpp"
 
+// 3rd party headers
 #include <boost/asio.hpp>
 
+// standard headers
 #include <atomic>
 #include <functional>
 #include <mutex>
diff --git a/client/player/pulse_player.hpp b/client/player/pulse_player.hpp
index 71a6cf99..a16033ba 100644
--- a/client/player/pulse_player.hpp
+++ b/client/player/pulse_player.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -19,13 +19,17 @@
 #ifndef PULSE_PLAYER_HPP
 #define PULSE_PLAYER_HPP
 
+// local headers
 #include "player.hpp"
 
+// 3rd party headers
+#include <pulse/pulseaudio.h>
+
+// standard headers
 #include <atomic>
 #include <cstdio>
 #include <memory>
 #include <optional>
-#include <pulse/pulseaudio.h>
 
 
 namespace player
diff --git a/client/player/wasapi_player.cpp b/client/player/wasapi_player.cpp
index e5f5dea5..9dd1b739 100644
--- a/client/player/wasapi_player.cpp
+++ b/client/player/wasapi_player.cpp
@@ -1,21 +1,47 @@
+/***
+    This file is part of snapcast
+    Copyright (C) 2014-2022  Johannes Pohl
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+***/
+
+// prototype/interface header file
 #include "wasapi_player.hpp"
+
+// local headers
+#include "common/aixlog.hpp"
+#include "common/snap_exception.hpp"
+
+// 3rd party headers
 #include <initguid.h>
 #include <mmdeviceapi.h>
 //#include <functiondiscoverykeys_devpkey.h>
-#include "common/aixlog.hpp"
-#include "common/snap_exception.hpp"
-#include <assert.h>
+
+// standard headers
 #include <audioclient.h>
 #include <avrt.h>
-#include <chrono>
-#include <codecvt>
 #include <comdef.h>
 #include <comip.h>
-#include <functional>
 #include <ksmedia.h>
-#include <locale>
 #include <mmdeviceapi.h>
 
+#include <cassert>
+#include <chrono>
+#include <codecvt>
+#include <functional>
+#include <locale>
+
 using namespace std;
 using namespace std::chrono;
 using namespace std::chrono_literals;
diff --git a/client/player/wasapi_player.hpp b/client/player/wasapi_player.hpp
index 2b209c13..cd9f74c3 100644
--- a/client/player/wasapi_player.hpp
+++ b/client/player/wasapi_player.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2016  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -22,10 +22,14 @@
 #pragma warning(push)
 #pragma warning(disable : 4100)
 
+// local headers
 #include "player.hpp"
+
+// 3rd party headers
 #include <audiopolicy.h>
 #include <endpointvolume.h>
 
+
 namespace player
 {
 
diff --git a/client/snapclient.cpp b/client/snapclient.cpp
index 7e157b32..619f164d 100644
--- a/client/snapclient.cpp
+++ b/client/snapclient.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,13 +16,7 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#include <chrono>
-#include <iostream>
-#ifndef WINDOWS
-#include <csignal>
-#include <sys/resource.h>
-#endif
-
+// local headers
 #include "common/popl.hpp"
 #include "controller.hpp"
 
@@ -46,9 +40,19 @@
 #include "common/utils.hpp"
 #include "common/version.hpp"
 
+// 3rd party headers
 #include <boost/asio/ip/host_name.hpp>
 #include <boost/asio/signal_set.hpp>
 
+// standard headers
+#include <chrono>
+#include <iostream>
+#ifndef WINDOWS
+#include <csignal>
+#include <sys/resource.h>
+#endif
+
+
 using namespace std;
 using namespace popl;
 using namespace player;
diff --git a/server/control_server.cpp b/server/control_server.cpp
index 13b5fa1a..888a91c3 100644
--- a/server/control_server.cpp
+++ b/server/control_server.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,7 +16,10 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+// prototype/interface header file
 #include "control_server.hpp"
+
+// local headers
 #include "common/aixlog.hpp"
 #include "common/snap_exception.hpp"
 #include "common/utils.hpp"
@@ -26,6 +29,9 @@
 #include "jsonrpcpp.hpp"
 #include "message/time.hpp"
 
+// 3rd party headers
+
+// standard headers
 #include <iostream>
 
 using namespace std;
diff --git a/server/control_server.hpp b/server/control_server.hpp
index fe9843ce..bfd2b211 100644
--- a/server/control_server.hpp
+++ b/server/control_server.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,15 +16,10 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef CONTROL_SERVER_H
-#define CONTROL_SERVER_H
-
-#include <boost/asio.hpp>
-#include <memory>
-#include <mutex>
-#include <set>
-#include <vector>
+#ifndef CONTROL_SERVER_HPP
+#define CONTROL_SERVER_HPP
 
+// local headers
 #include "common/queue.h"
 #include "common/sample_format.hpp"
 #include "control_session.hpp"
@@ -33,6 +28,16 @@
 #include "message/server_settings.hpp"
 #include "server_settings.hpp"
 
+// 3rd party headers
+#include <boost/asio.hpp>
+
+// standard headers
+#include <memory>
+#include <mutex>
+#include <set>
+#include <vector>
+
+
 using boost::asio::ip::tcp;
 using acceptor_ptr = std::unique_ptr<tcp::acceptor>;
 
diff --git a/server/control_session.hpp b/server/control_session.hpp
index d3c49cb2..ae7ada68 100644
--- a/server/control_session.hpp
+++ b/server/control_session.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,14 +16,19 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#ifndef CONTROL_SESSION_H
-#define CONTROL_SESSION_H
+#ifndef CONTROL_SESSION_HPP
+#define CONTROL_SESSION_HPP
 
+// local headers
 #include "common/queue.h"
 #include "message/message.hpp"
 #include "server_settings.hpp"
-#include <atomic>
+
+// 3rd party headers
 #include <boost/asio.hpp>
+
+// standard headers
+#include <atomic>
 #include <condition_variable>
 #include <memory>
 #include <set>
diff --git a/server/control_session_http.hpp b/server/control_session_http.hpp
index 77c1a826..8eb234fc 100644
--- a/server/control_session_http.hpp
+++ b/server/control_session_http.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -19,7 +19,10 @@
 #ifndef CONTROL_SESSION_HTTP_HPP
 #define CONTROL_SESSION_HTTP_HPP
 
+// local headers
 #include "control_session.hpp"
+
+// 3rd party headers
 #include <boost/beast/core.hpp>
 #if defined(__GNUC__) && !defined(__clang__)
 #pragma GCC diagnostic push
@@ -29,6 +32,8 @@
 #else
 #include <boost/beast/websocket.hpp>
 #endif
+
+// standard headers
 #include <deque>
 
 using boost::asio::ip::tcp;
diff --git a/server/control_session_tcp.cpp b/server/control_session_tcp.cpp
index a53d848e..52a7b67d 100644
--- a/server/control_session_tcp.cpp
+++ b/server/control_session_tcp.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,10 +16,14 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+// prototype/interface header file
 #include "control_session_tcp.hpp"
+
+// local headers
 #include "common/aixlog.hpp"
 #include "message/pcm_chunk.hpp"
 
+
 using namespace std;
 
 static constexpr auto LOG_TAG = "ControlSessionTCP";
diff --git a/server/control_session_tcp.hpp b/server/control_session_tcp.hpp
index f3056a04..29e113ec 100644
--- a/server/control_session_tcp.hpp
+++ b/server/control_session_tcp.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -19,7 +19,13 @@
 #ifndef CONTROL_SESSION_TCP_HPP
 #define CONTROL_SESSION_TCP_HPP
 
+// local headers
 #include "control_session.hpp"
+
+// 3rd party headers
+#include <boost/asio.hpp>
+
+// standard headers
 #include <deque>
 
 using boost::asio::ip::tcp;
diff --git a/server/control_session_ws.cpp b/server/control_session_ws.cpp
index 24ba2b56..8aeda904 100644
--- a/server/control_session_ws.cpp
+++ b/server/control_session_ws.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,9 +16,14 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+// local headers
 #include "control_session_ws.hpp"
 #include "common/aixlog.hpp"
 #include "message/pcm_chunk.hpp"
+
+// 3rd party headers
+
+// standard headers
 #include <iostream>
 
 using namespace std;
diff --git a/server/control_session_ws.hpp b/server/control_session_ws.hpp
index 574186b2..dcade5ee 100644
--- a/server/control_session_ws.hpp
+++ b/server/control_session_ws.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -19,9 +19,14 @@
 #ifndef CONTROL_SESSION_WS_HPP
 #define CONTROL_SESSION_WS_HPP
 
+// local headers
 #include "control_session.hpp"
+
+// 3rd party headers
 #include <boost/beast/core.hpp>
 #include <boost/beast/websocket.hpp>
+
+// standard headers
 #include <deque>
 
 namespace beast = boost::beast;         // from <boost/beast.hpp>
diff --git a/server/publishZeroConf/publish_avahi.cpp b/server/publishZeroConf/publish_avahi.cpp
index 70f1dfd1..01a520cc 100644
--- a/server/publishZeroConf/publish_avahi.cpp
+++ b/server/publishZeroConf/publish_avahi.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,8 +16,15 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+// prototype/interface header file
 #include "publish_avahi.hpp"
+
+// local headers
 #include "common/aixlog.hpp"
+
+// 3rd party headers
+
+// standard headers
 #include <cstdio>
 #include <cstdlib>
 
diff --git a/server/publishZeroConf/publish_avahi.hpp b/server/publishZeroConf/publish_avahi.hpp
index b4b26d48..4d8023fe 100644
--- a/server/publishZeroConf/publish_avahi.hpp
+++ b/server/publishZeroConf/publish_avahi.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -17,18 +17,22 @@
 ***/
 
 
-#ifndef PUBLISH_AVAHI_H
-#define PUBLISH_AVAHI_H
+#ifndef PUBLISH_AVAHI_HPP
+#define PUBLISH_AVAHI_HPP
 
+// local headers
+
+// 3rd party headers
 #include <avahi-client/client.h>
 #include <avahi-client/publish.h>
-
-#include <atomic>
 #include <avahi-common/alternative.h>
 #include <avahi-common/error.h>
 #include <avahi-common/malloc.h>
 #include <avahi-common/simple-watch.h>
 #include <avahi-common/timeval.h>
+
+// standard headers
+#include <atomic>
 #include <string>
 #include <vector>
 
diff --git a/server/publishZeroConf/publish_bonjour.cpp b/server/publishZeroConf/publish_bonjour.cpp
index 09bc0af4..3afe7724 100644
--- a/server/publishZeroConf/publish_bonjour.cpp
+++ b/server/publishZeroConf/publish_bonjour.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,11 +16,18 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+// prototype/interface header file
+#include "publish_bonjour.hpp"
+
+// local headers
+#include "common/aixlog.hpp"
+
+// 3rd party headers
+
+// standard headers
 #include <cstdlib>
 #include <thread>
 
-#include "common/aixlog.hpp"
-#include "publish_bonjour.hpp"
 
 static constexpr auto LOG_TAG = "Bonjour";
 
diff --git a/server/publishZeroConf/publish_bonjour.hpp b/server/publishZeroConf/publish_bonjour.hpp
index 2099e32b..3df78539 100644
--- a/server/publishZeroConf/publish_bonjour.hpp
+++ b/server/publishZeroConf/publish_bonjour.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -17,10 +17,13 @@
 ***/
 
 
-#ifndef PUBLISH_BONJOUR_H
-#define PUBLISH_BONJOUR_H
+#ifndef PUBLISH_BONJOUR_HPP
+#define PUBLISH_BONJOUR_HPP
 
+// 3rd party headers
 #include <dns_sd.h>
+
+// standard headers
 #include <string>
 
 class PublishBonjour;
diff --git a/server/publishZeroConf/publish_mdns.hpp b/server/publishZeroConf/publish_mdns.hpp
index de673bdd..54798cab 100644
--- a/server/publishZeroConf/publish_mdns.hpp
+++ b/server/publishZeroConf/publish_mdns.hpp
@@ -1,7 +1,28 @@
-#ifndef PUBLISH_MDNS_H
-#define PUBLISH_MDNS_H
+/***
+    This file is part of snapcast
+    Copyright (C) 2014-2022  Johannes Pohl
 
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#ifndef PUBLISH_MDNS_HPP
+#define PUBLISH_MDNS_HPP
+
+// 3rd party headers
 #include <boost/asio.hpp>
+
+// standard headers
 #include <string>
 #include <vector>
 
diff --git a/server/snapserver.cpp b/server/snapserver.cpp
index 4fd94c64..c281e301 100644
--- a/server/snapserver.cpp
+++ b/server/snapserver.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,10 +16,7 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#include <chrono>
-#include <memory>
-#include <sys/resource.h>
-
+// local headers
 #include "common/popl.hpp"
 #ifdef HAS_DAEMON
 #include "common/daemon.hpp"
@@ -39,8 +36,15 @@
 #include "common/aixlog.hpp"
 #include "config.hpp"
 
+// 3rd party headers
 #include <boost/asio/ip/host_name.hpp>
 
+// standard headers
+#include <chrono>
+#include <memory>
+#include <sys/resource.h>
+
+
 using namespace std;
 using namespace popl;
 
diff --git a/server/stream_session.hpp b/server/stream_session.hpp
index c296705c..a268854b 100644
--- a/server/stream_session.hpp
+++ b/server/stream_session.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -19,6 +19,15 @@
 #ifndef STREAM_SESSION_HPP
 #define STREAM_SESSION_HPP
 
+// local headers
+#include "common/queue.h"
+#include "message/message.hpp"
+#include "streamreader/stream_manager.hpp"
+
+// 3rd party headers
+#include <boost/asio.hpp>
+
+// standard headers
 #include <atomic>
 #include <condition_variable>
 #include <deque>
@@ -29,12 +38,6 @@
 #include <string>
 #include <vector>
 
-#include <boost/asio.hpp>
-
-#include "common/queue.h"
-#include "message/message.hpp"
-#include "streamreader/stream_manager.hpp"
-
 
 namespace net = boost::asio;
 
diff --git a/server/stream_session_tcp.cpp b/server/stream_session_tcp.cpp
index a7f9a2ab..34f21de2 100644
--- a/server/stream_session_tcp.cpp
+++ b/server/stream_session_tcp.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,10 +16,16 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+// prototype/interface header file
 #include "stream_session_tcp.hpp"
 
+// local headers
 #include "common/aixlog.hpp"
 #include "message/pcm_chunk.hpp"
+
+// 3rd party headers
+
+// standard headers
 #include <iostream>
 
 using namespace std;
diff --git a/server/stream_session_tcp.hpp b/server/stream_session_tcp.hpp
index 7952b72c..bc85a7a9 100644
--- a/server/stream_session_tcp.hpp
+++ b/server/stream_session_tcp.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -19,8 +19,13 @@
 #ifndef STREAM_SESSION_TCP_HPP
 #define STREAM_SESSION_TCP_HPP
 
+// local headers
 #include "stream_session.hpp"
 
+// 3rd party headers
+
+// standard headers
+
 using boost::asio::ip::tcp;
 
 
diff --git a/server/stream_session_ws.cpp b/server/stream_session_ws.cpp
index 903754e9..08b1a938 100644
--- a/server/stream_session_ws.cpp
+++ b/server/stream_session_ws.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2021  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,9 +16,16 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+// prototype/interface header file
 #include "stream_session_ws.hpp"
+
+// local headers
 #include "common/aixlog.hpp"
 #include "message/pcm_chunk.hpp"
+
+// 3rd party headers
+
+// standard headers
 #include <iostream>
 
 using namespace std;
diff --git a/server/streamreader/watchdog.cpp b/server/streamreader/watchdog.cpp
index e9ec333e..227d6f24 100644
--- a/server/streamreader/watchdog.cpp
+++ b/server/streamreader/watchdog.cpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -16,8 +16,15 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+// prototype/interface header file
 #include "watchdog.hpp"
+
+// local headers
 #include "common/aixlog.hpp"
+
+// 3rd party headers
+
+// standard headers
 #include <chrono>
 
 
diff --git a/server/streamreader/watchdog.hpp b/server/streamreader/watchdog.hpp
index c4e9df68..7f180afd 100644
--- a/server/streamreader/watchdog.hpp
+++ b/server/streamreader/watchdog.hpp
@@ -1,6 +1,6 @@
 /***
     This file is part of snapcast
-    Copyright (C) 2014-2020  Johannes Pohl
+    Copyright (C) 2014-2022  Johannes Pohl
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -19,7 +19,10 @@
 #ifndef WATCH_DOG_HPP
 #define WATCH_DOG_HPP
 
+// 3rd party headers
 #include <boost/asio.hpp>
+
+// standard headers
 #include <memory>
 
 namespace net = boost::asio;