Merge branch 'master' into jgrpp

# Conflicts: # .github/workflows/ci-build.yml # .github/workflows/release-linux.yml # .github/workflows/release-macos.yml # .github/workflows/release-source.yml # .github/workflows/release.yml # CMakeLists.txt # COMPILING.md # src/ai/ai_core.cpp # src/ai/ai_gui.cpp # src/bridge_gui.cpp # src/company_gui.cpp # src/console_cmds.cpp # src/core/CMakeLists.txt # src/core/smallmap_type.hpp # src/disaster_vehicle.h # src/effectvehicle_base.h # src/fontcache.cpp # src/game/game_core.cpp # src/game/game_gui.cpp # src/gamelog.cpp # src/gamelog_internal.h # src/group_gui.cpp # src/linkgraph/linkgraph.h # src/misc.cpp # src/network/core/config.h # src/network/core/udp.cpp # src/network/network_chat_gui.cpp # src/network/network_content_gui.cpp # src/network/network_gui.cpp # src/newgrf.cpp # src/newgrf_gui.cpp # src/newgrf_profiling.cpp # src/newgrf_profiling.h # src/object_gui.cpp # src/openttd.cpp # src/openttd.h # src/order_gui.cpp # src/os/windows/font_win32.cpp # src/rail_gui.cpp # src/road.cpp # src/road_gui.cpp # src/saveload/afterload.cpp # src/saveload/saveload.h # src/script/api/script_controller.cpp # src/script/api/script_roadtypelist.cpp # src/script/script_config.cpp # src/script/script_config.hpp # src/script/script_instance.cpp # src/script/script_scanner.cpp # src/script/squirrel.cpp # src/script/squirrel_helper.hpp # src/settings_gui.cpp # src/settings_internal.h # src/settings_type.h # src/table/settings/network_private_settings.ini # src/timetable_gui.cpp # src/vehicle.cpp # src/vehicle_base.h # src/window_gui.h
2023-07-01 01:08:35 +01:00
parent 87ee18b6b9 91e140c722
commit d09b504bc5
246 changed files with 2023 additions and 1211 deletions
--- a/src/network/CMakeLists.txt
+++ b/src/network/CMakeLists.txt
@@ -28,6 +28,8 @@ add_files(
    network_server.h
    network_stun.cpp
    network_stun.h
+    network_survey.cpp
+    network_survey.h
    network_turn.cpp
    network_turn.h
    network_type.h
--- a/src/network/core/address.cpp
+++ b/src/network/core/address.cpp
@@ -282,7 +282,7 @@ SOCKET NetworkAddress::Resolve(int family, int socktype, int flags, SocketList *
 		 * of course totally unneeded ;) */
 		if (sockets != nullptr) {
 			NetworkAddress address(runp->ai_addr, (int)runp->ai_addrlen);
-			if (sockets->Contains(address)) continue;
+			if (std::any_of(sockets->begin(), sockets->end(), [&address](const auto &p) { return p.second == address; })) continue;
 		}
 		sock = func(runp);
 		if (sock == INVALID_SOCKET) continue;
@@ -307,7 +307,7 @@ SOCKET NetworkAddress::Resolve(int family, int socktype, int flags, SocketList *
 		}

 		NetworkAddress addr(runp->ai_addr, (int)runp->ai_addrlen);
-		(*sockets)[addr] = sock;
+		(*sockets)[sock] = addr;
 		sock = INVALID_SOCKET;
 	}
 	freeaddrinfo (ai);
--- a/src/network/core/address.h
+++ b/src/network/core/address.h
@@ -14,13 +14,13 @@
 #include "config.h"
 #include "../../company_type.h"
 #include "../../string_func.h"
-#include "../../core/smallmap_type.hpp"

+#include <map>
 #include <string>

 class NetworkAddress;
 typedef std::vector<NetworkAddress> NetworkAddressList; ///< Type for a list of addresses.
-typedef SmallMap<NetworkAddress, SOCKET> SocketList;    ///< Type for a mapping between address and socket.
+using SocketList = std::map<SOCKET, NetworkAddress>;    ///< Type for a mapping between address and socket.

 /**
 * Wrapper for (un)resolved network addresses; there's no reason to transform
--- a/src/network/core/config.cpp
+++ b/src/network/core/config.cpp
@@ -67,3 +67,13 @@ const char *NetworkContentMirrorUriString()
 {
 	return GetEnv("OTTD_CONTENT_MIRROR_URI", "https://binaries.openttd.org/bananas");
 }
+
+/**
+ * Get the URI string for the survey from the environment variable OTTD_SURVEY_URI,
+ * or when it has not been set a hard coded URI of the production server.
+ * @return The survey's URI string.
+ */
+const char *NetworkSurveyUriString()
+{
+	return GetEnv("OTTD_SURVEY_URI", "https://survey-participate.openttd.org/");
+}
--- a/src/network/core/config.h
+++ b/src/network/core/config.h
@@ -16,6 +16,7 @@ const char *NetworkCoordinatorConnectionString();
 const char *NetworkStunConnectionString();
 const char *NetworkContentServerConnectionString();
 const char *NetworkContentMirrorUriString();
+const char *NetworkSurveyUriString();

 static const uint16 NETWORK_COORDINATOR_SERVER_PORT = 3976;           ///< The default port of the Game Coordinator server (TCP)
 static const uint16 NETWORK_STUN_SERVER_PORT        = 3975;           ///< The default port of the STUN server (TCP)
@@ -27,6 +28,8 @@ static const uint16 NETWORK_DEFAULT_DEBUGLOG_PORT   = 3982;           ///< The d

 static const uint16 UDP_MTU                         = 1460;           ///< Number of bytes we can pack in a single UDP packet
 static const uint16 UDP_MTU_SHORT                   = 1400;           ///< Number of bytes we can pack in a single UDP packet (conservative)
+
+static const std::string NETWORK_SURVEY_DETAILS_LINK = "https://survey.openttd.org/participate"; ///< Link with more details & privacy statement of the survey.
 /*
 * Technically a TCP packet could become 64kiB, however the high bit is kept so it becomes possible in the future
 * to go to (significantly) larger packets if needed. This would entail a strategy such as employed for UTF-8.
@@ -47,6 +50,7 @@ static const uint16 COMPAT_MTU                      = 1460;           ///< Numbe
 static const byte NETWORK_GAME_ADMIN_VERSION        =    3;           ///< What version of the admin network do we use?
 static const byte NETWORK_GAME_INFO_VERSION         =    6;           ///< What version of game-info do we use?
 static const byte NETWORK_COORDINATOR_VERSION       =    6;           ///< What version of game-coordinator-protocol do we use?
+static const byte NETWORK_SURVEY_VERSION            =    1;           ///< What version of the survey do we use?

 static const uint NETWORK_NAME_LENGTH               =   80;           ///< The maximum length of the server name and map name, in bytes including '\0'
 static const uint NETWORK_COMPANY_NAME_LENGTH       =  128;           ///< The maximum length of the company name, in bytes including '\0'
--- a/src/network/core/core.h
+++ b/src/network/core/core.h
@@ -48,7 +48,7 @@ public:
 	NetworkSocketHandler() { this->has_quit = false; }

 	/** Close the socket when destructing the socket handler */
-	virtual ~NetworkSocketHandler() {}
+	virtual ~NetworkSocketHandler() = default;

 	/**
 	 * Mark the connection as closed.
--- a/src/network/core/host.cpp
+++ b/src/network/core/host.cpp
@@ -9,6 +9,7 @@

 #include "../../stdafx.h"
 #include "../../debug.h"
+#include "../../core/alloc_func.hpp"
 #include "address.h"

 #include "../../safeguards.h"
--- a/src/network/core/http.h
+++ b/src/network/core/http.h
@@ -14,6 +14,8 @@

 #include "tcp.h"

+constexpr int HTTP_429_TOO_MANY_REQUESTS = 429;
+
 /** Callback for when the HTTP handler has something to tell us. */
 struct HTTPCallback {
 	/**
@@ -40,7 +42,7 @@ struct HTTPCallback {
 	virtual bool IsCancelled() const = 0;

 	/** Silentium */
-	virtual ~HTTPCallback() {}
+	virtual ~HTTPCallback() = default;
 };

 /** Base socket handler for HTTP traffic. */
--- a/src/network/core/http_curl.cpp
+++ b/src/network/core/http_curl.cpp
@@ -117,6 +117,7 @@ void HttpThread()

 		/* Reset to default settings. */
 		curl_easy_reset(curl);
+		curl_slist *headers = nullptr;

 		if (_debug_net_level >= 5) {
 			curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
@@ -147,8 +148,16 @@ void HttpThread()

 		/* Prepare POST body and URI. */
 		if (!request->data.empty()) {
+			/* When the payload starts with a '{', it is a JSON payload. */
+			if (StrStartsWith(request->data, "{")) {
+				headers = curl_slist_append(headers, "Content-Type: application/json");
+			} else {
+				headers = curl_slist_append(headers, "Content-Type: application/x-www-form-urlencoded");
+			}
+
 			curl_easy_setopt(curl, CURLOPT_POST, 1L);
 			curl_easy_setopt(curl, CURLOPT_POSTFIELDS, request->data.c_str());
+			curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
 		}
 		curl_easy_setopt(curl, CURLOPT_URL, request->uri.c_str());

@@ -175,11 +184,17 @@ void HttpThread()
 		/* Perform the request. */
 		CURLcode res = curl_easy_perform(curl);

+		curl_slist_free_all(headers);
+
 		if (res == CURLE_OK) {
 			Debug(net, 1, "HTTP request succeeded");
 			request->callback->OnReceiveData(nullptr, 0);
 		} else {
-			Debug(net, (request->callback->IsCancelled() || _http_thread_exit) ? 1 : 0, "HTTP request failed: {}", curl_easy_strerror(res));
+			long status_code = 0;
+			curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &status_code);
+
+			/* No need to be verbose about rate limiting. */
+			Debug(net, (request->callback->IsCancelled() || _http_thread_exit || status_code == HTTP_429_TOO_MANY_REQUESTS) ? 1 : 0, "HTTP request failed: status_code: {}, error: {}", status_code, curl_easy_strerror(res));
 			request->callback->OnFailure();
 		}
 	}
--- a/src/network/core/http_winhttp.cpp
+++ b/src/network/core/http_winhttp.cpp
@@ -131,7 +131,8 @@ void NetworkHTTPRequest::WinHttpCallback(DWORD code, void *info, DWORD length)

 			/* If there is any error, we simply abort the request. */
 			if (status_code >= 400) {
-				Debug(net, 0, "HTTP request failed: status-code {}", status_code);
+				/* No need to be verbose about rate limiting. */
+				Debug(net, status_code == HTTP_429_TOO_MANY_REQUESTS ? 1 : 0, "HTTP request failed: status-code {}", status_code);
 				this->finished = true;
 				this->callback->OnFailure();
 				return;
@@ -242,7 +243,9 @@ void NetworkHTTPRequest::Connect()
 	if (data.empty()) {
 		WinHttpSendRequest(this->request, WINHTTP_NO_ADDITIONAL_HEADERS, 0, WINHTTP_NO_REQUEST_DATA, 0, 0, reinterpret_cast<DWORD_PTR>(this));
 	} else {
-		WinHttpSendRequest(this->request, L"Content-Type: application/x-www-form-urlencoded\r\n", -1, const_cast<char *>(data.c_str()), static_cast<DWORD>(data.size()), static_cast<DWORD>(data.size()), reinterpret_cast<DWORD_PTR>(this));
+		/* When the payload starts with a '{', it is a JSON payload. */
+		LPCWSTR content_type = StrStartsWith(data, "{") ? L"Content-Type: application/json\r\n" : L"Content-Type: application/x-www-form-urlencoded\r\n";
+		WinHttpSendRequest(this->request, content_type, -1, const_cast<char *>(data.c_str()), static_cast<DWORD>(data.size()), static_cast<DWORD>(data.size()), reinterpret_cast<DWORD_PTR>(this));
 	}
 }

--- a/src/network/core/tcp_game.h
+++ b/src/network/core/tcp_game.h
@@ -565,7 +565,7 @@ public:
 	 * @param status The reason the connection got closed.
 	 */
 	virtual NetworkRecvStatus CloseConnection(NetworkRecvStatus status) = 0;
-	virtual ~NetworkGameSocketHandler() {}
+	virtual ~NetworkGameSocketHandler() = default;

 	/**
 	 * Sets the client info for this socket handler.
--- a/src/network/core/tcp_listen.h
+++ b/src/network/core/tcp_listen.h
@@ -114,7 +114,7 @@ public:

 		/* take care of listener port */
 		for (auto &s : sockets) {
-			FD_SET(s.second, &read_fd);
+			FD_SET(s.first, &read_fd);
 		}

 		tv.tv_sec = tv.tv_usec = 0; // don't block at all.
@@ -122,7 +122,7 @@ public:

 		/* accept clients.. */
 		for (auto &s : sockets) {
-			if (FD_ISSET(s.second, &read_fd)) AcceptClient(s.second);
+			if (FD_ISSET(s.first, &read_fd)) AcceptClient(s.first);
 		}

 		/* read stuff from clients */
@@ -164,7 +164,7 @@ public:
 	static void CloseListeners()
 	{
 		for (auto &s : sockets) {
-			closesocket(s.second);
+			closesocket(s.first);
 		}
 		sockets.clear();
 		DEBUG(net, 5, "[%s] Closed listeners", Tsocket::GetName());
--- a/src/network/core/udp.cpp
+++ b/src/network/core/udp.cpp
@@ -61,7 +61,7 @@ bool NetworkUDPSocketHandler::Listen()
 void NetworkUDPSocketHandler::CloseSocket()
 {
 	for (auto &s : this->sockets) {
-		closesocket(s.second);
+		closesocket(s.first);
 	}
 	this->sockets.clear();
 }
@@ -113,20 +113,20 @@ void NetworkUDPSocketHandler::SendPacket(Packet *p, NetworkAddress *recv, bool a
 		NetworkAddress send(*recv);

 		/* Not the same type */
-		if (!send.IsFamily(s.first.GetAddress()->ss_family)) continue;
+		if (!send.IsFamily(s.second.GetAddress()->ss_family)) continue;

 		p->PrepareToSend();

 		if (broadcast) {
 			/* Enable broadcast */
 			unsigned long val = 1;
-			if (setsockopt(s.second, SOL_SOCKET, SO_BROADCAST, (char *) &val, sizeof(val)) < 0) {
+			if (setsockopt(s.first, SOL_SOCKET, SO_BROADCAST, (char *) &val, sizeof(val)) < 0) {
 				DEBUG(net, 1, "Setting broadcast mode failed: %s", NetworkError::GetLast().AsString());
 			}
 		}

 		/* Send the buffer */
-		ssize_t res = p->TransferOut<int>(sendto, s.second, 0, (const struct sockaddr *)send.GetAddress(), send.GetAddressLength());
+		ssize_t res = p->TransferOut<int>(sendto, s.first, 0, (const struct sockaddr *)send.GetAddress(), send.GetAddressLength());
 		DEBUG(net, 7, "sendto(%s)",  NetworkAddressDumper().GetAddressAsString(&send));

 		/* Check for any errors, but ignore it otherwise */
@@ -151,8 +151,8 @@ void NetworkUDPSocketHandler::ReceivePackets()
 			socklen_t client_len = sizeof(client_addr);

 			/* Try to receive anything */
-			SetNonBlocking(s.second); // Some OSes seem to lose the non-blocking status of the socket
-			ssize_t nbytes = p.TransferIn<int>(recvfrom, s.second, 0, (struct sockaddr *)&client_addr, &client_len);
+			SetNonBlocking(s.first); // Some OSes seem to lose the non-blocking status of the socket
+			ssize_t nbytes = p.TransferIn<int>(recvfrom, s.first, 0, (struct sockaddr *)&client_addr, &client_len);

 			/* Did we get the bytes for the base header of the packet? */
 			if (nbytes <= 0) break;    // No data, i.e. no packet
--- a/src/network/network.cpp
+++ b/src/network/network.cpp
@@ -102,6 +102,8 @@ static_assert((int)NETWORK_COMPANY_NAME_LENGTH == MAX_LENGTH_COMPANY_NAME_CHARS
 /** The amount of clients connected */
 byte _network_clients_connected = 0;

+extern std::string GenerateUid(std::string_view subject);
+
 /**
 * Return whether there is any client connected or trying to connect at all.
 * @return whether we have any client activity
@@ -1298,24 +1300,7 @@ void NetworkGameLoop()

 static void NetworkGenerateServerId()
 {
-	Md5 checksum;
-	uint8 digest[16];
-	char hex_output[16 * 2 + 1];
-	char coding_string[NETWORK_NAME_LENGTH];
-	int di;
-
-	seprintf(coding_string, lastof(coding_string), "%d%s", (uint)Random(), "OpenTTD Server ID");
-
-	/* Generate the MD5 hash */
-	checksum.Append((const uint8*)coding_string, strlen(coding_string));
-	checksum.Finish(digest);
-
-	for (di = 0; di < 16; ++di) {
-		seprintf(hex_output + di * 2, lastof(hex_output), "%02x", digest[di]);
-	}
-
-	/* _settings_client.network.network_id is our id */
-	_settings_client.network.network_id = hex_output;
+	_settings_client.network.network_id = GenerateUid("OpenTTD Server ID");
 }

 std::string BytesToHexString(const byte *data, uint length)
--- a/src/network/network_chat_gui.cpp
+++ b/src/network/network_chat_gui.cpp
@@ -21,6 +21,7 @@
 #include "network.h"
 #include "network_client.h"
 #include "network_base.h"
+#include "../3rdparty/fmt/format.h"

 #include "../widgets/network_chat_widget.h"

@@ -28,6 +29,7 @@

 #include <stdarg.h> /* va_list */
 #include <deque>
+#include <optional>

 #include "../safeguards.h"

@@ -326,18 +328,16 @@ struct NetworkChatWindow : public Window {
 	 * Find the next item of the list of things that can be auto-completed.
 	 * @param item The current indexed item to return. This function can, and most
 	 *     likely will, alter item, to skip empty items in the arrays.
-	 * @return Returns the char that matched to the index.
+	 * @return Returns the view that matched to the index.
 	 */
-	const char *ChatTabCompletionNextItem(uint *item)
+	std::optional<std::string> ChatTabCompletionNextItem(uint *item)
 	{
-		static char chat_tab_temp_buffer[64];
-
 		/* First, try clients */
 		if (*item < MAX_CLIENT_SLOTS) {
 			/* Skip inactive clients */
 			for (NetworkClientInfo *ci : NetworkClientInfo::Iterate(*item)) {
 				*item = ci->index;
-				return ci->client_name.c_str();
+				return ci->client_name;
 			}
 			*item = MAX_CLIENT_SLOTS;
 		}
@@ -349,12 +349,11 @@ struct NetworkChatWindow : public Window {
 			for (const Town *t : Town::Iterate(*item - MAX_CLIENT_SLOTS)) {
 				/* Get the town-name via the string-system */
 				SetDParam(0, t->index);
-				GetString(chat_tab_temp_buffer, STR_TOWN_NAME, lastof(chat_tab_temp_buffer));
-				return &chat_tab_temp_buffer[0];
+				return GetString(STR_TOWN_NAME);
 			}
 		}

-		return nullptr;
+		return std::nullopt;
 	}

 	/**
@@ -362,13 +361,14 @@ struct NetworkChatWindow : public Window {
 	 *  the word right from that as to complete. It also writes a \0 at the
 	 *  position of the space (if any). If nothing found, buf is returned.
 	 */
-	static char *ChatTabCompletionFindText(char *buf)
+	static std::string_view ChatTabCompletionFindText(std::string_view &buf)
 	{
-		char *p = strrchr(buf, ' ');
-		if (p == nullptr) return buf;
+		auto it = buf.find_last_of(' ');
+		if (it == std::string_view::npos) return buf;

-		*p = '\0';
-		return p + 1;
+		std::string_view res = buf.substr(it + 1);
+		buf.remove_suffix(res.size() + 1);
+		return res;
 	}

 	/**
@@ -376,46 +376,44 @@ struct NetworkChatWindow : public Window {
 	 */
 	void ChatTabCompletion()
 	{
-		static char _chat_tab_completion_buf[NETWORK_CHAT_LENGTH];
-		assert(this->message_editbox.text.max_bytes == lengthof(_chat_tab_completion_buf));
+		static std::string _chat_tab_completion_buf;

 		Textbuf *tb = &this->message_editbox.text;
-		size_t len, tb_len;
-		uint item;
-		char *tb_buf, *pre_buf;
-		const char *cur_name;
+		uint item = 0;
 		bool second_scan = false;

-		item = 0;
+		/* Create views, so we do not need to copy the data for now. */
+		std::string_view pre_buf = _chat_tab_completion_active ? std::string_view(_chat_tab_completion_buf) : std::string_view(tb->buf);
+		std::string_view tb_buf = ChatTabCompletionFindText(pre_buf);

-		/* Copy the buffer so we can modify it without damaging the real data */
-		pre_buf = (_chat_tab_completion_active) ? stredup(_chat_tab_completion_buf) : stredup(tb->buf);
+		/*
+		 * Comparing pointers of the data, as both "Hi:<tab>" and "Hi: Hi:<tab>" will result in
+		 * tb_buf and pre_buf being "Hi:", which would be equal in content but not in context.
+		 */
+		bool begin_of_line = tb_buf.data() == pre_buf.data();

-		tb_buf  = ChatTabCompletionFindText(pre_buf);
-		tb_len  = strlen(tb_buf);
-
-		while ((cur_name = ChatTabCompletionNextItem(&item)) != nullptr) {
+		std::optional<std::string> cur_item;
+		while ((cur_item = ChatTabCompletionNextItem(&item)).has_value()) {
+			std::string_view cur_name = cur_item.value();
 			item++;

 			if (_chat_tab_completion_active) {
 				/* We are pressing TAB again on the same name, is there another name
 				 *  that starts with this? */
 				if (!second_scan) {
-					size_t offset;
-					size_t length;
+					std::string_view view;

 					/* If we are completing at the begin of the line, skip the ': ' we added */
-					if (tb_buf == pre_buf) {
-						offset = 0;
-						length = (tb->bytes - 1) - 2;
+					if (begin_of_line) {
+						view = std::string_view(tb->buf, (tb->bytes - 1) - 2);
 					} else {
 						/* Else, find the place we are completing at */
-						offset = strlen(pre_buf) + 1;
-						length = (tb->bytes - 1) - offset;
+						size_t offset = pre_buf.size() + 1;
+						view = std::string_view(tb->buf + offset, (tb->bytes - 1) - offset);
 					}

 					/* Compare if we have a match */
-					if (strlen(cur_name) == length && strncmp(cur_name, tb->buf + offset, length) == 0) second_scan = true;
+					if (cur_name == view) second_scan = true;

 					continue;
 				}
@@ -423,21 +421,19 @@ struct NetworkChatWindow : public Window {
 				/* Now any match we make on _chat_tab_completion_buf after this, is perfect */
 			}

-			len = strlen(cur_name);
-			if (tb_len < len && StrStartsWith(cur_name, tb_buf)) {
+			if (tb_buf.size() < cur_name.size() && StrStartsWith(cur_name, tb_buf)) {
 				/* Save the data it was before completion */
-				if (!second_scan) seprintf(_chat_tab_completion_buf, lastof(_chat_tab_completion_buf), "%s", tb->buf);
+				if (!second_scan) _chat_tab_completion_buf = tb->buf;
 				_chat_tab_completion_active = true;

 				/* Change to the found name. Add ': ' if we are at the start of the line (pretty) */
-				if (pre_buf == tb_buf) {
-					this->message_editbox.text.Print("%s: ", cur_name);
+				if (begin_of_line) {
+					this->message_editbox.text.Assign(fmt::format("{}: ", cur_name));
 				} else {
-					this->message_editbox.text.Print("%s %s", pre_buf, cur_name);
+					this->message_editbox.text.Assign(fmt::format("{} {}", pre_buf, cur_name));
 				}

 				this->SetDirty();
-				free(pre_buf);
 				return;
 			}
 		}
@@ -449,7 +445,6 @@ struct NetworkChatWindow : public Window {

 			this->SetDirty();
 		}
-		free(pre_buf);
 	}

 	Point OnInitialPosition(int16 sm_width, int16 sm_height, int window_number) override
--- a/src/network/network_client.cpp
+++ b/src/network/network_client.cpp
@@ -31,6 +31,7 @@
 #include "../thread.h"
 #include "../crashlog.h"
 #include "../core/checksum_func.hpp"
+#include "../core/alloc_func.hpp"
 #include "../fileio_func.h"
 #include "../debug_settings.h"
 #include "../3rdparty/monocypher/monocypher.h"
--- a/src/network/network_content.h
+++ b/src/network/network_content.h
@@ -57,7 +57,7 @@ struct ContentCallback {
 	virtual void OnDownloadComplete(ContentID cid) {}

 	/** Silentium */
-	virtual ~ContentCallback() {}
+	virtual ~ContentCallback() = default;
 };

 /**
--- a/src/network/network_content_gui.cpp
+++ b/src/network/network_content_gui.cpp
@@ -791,7 +791,7 @@ public:

 	void OnClick(Point pt, int widget, int click_count) override
 	{
-		if (widget >= WID_NCL_TEXTFILE && widget < WID_NCL_TEXTFILE + TFT_END) {
+		if (widget >= WID_NCL_TEXTFILE && widget < WID_NCL_TEXTFILE + TFT_CONTENT_END) {
 			if (this->selected == nullptr || this->selected->state != ContentInfo::ALREADY_HERE) return;

 			ShowContentTextfileWindow((TextfileType)(widget - WID_NCL_TEXTFILE), this->selected);
@@ -800,11 +800,11 @@ public:

 		switch (widget) {
 			case WID_NCL_MATRIX: {
-				uint id_v = this->vscroll->GetScrolledRowFromWidget(pt.y, this, WID_NCL_MATRIX);
-				if (id_v >= this->content.size()) return; // click out of bounds
+				auto it = this->vscroll->GetScrolledItemFromWidget(this->content, pt.y, this, WID_NCL_MATRIX);
+				if (it == this->content.end()) return; // click out of bounds

-				this->selected = this->content[id_v];
-				this->list_pos = id_v;
+				this->selected = *it;
+				this->list_pos = it - this->content.begin();

 				const NWidgetBase *checkbox = this->GetWidget<NWidgetBase>(WID_NCL_CHECKBOX);
 				if (click_count > 1 || IsInsideBS(pt.x, checkbox->pos_x, checkbox->current_x)) {
@@ -998,7 +998,7 @@ public:
 		this->SetWidgetDisabledState(WID_NCL_SELECT_ALL, !show_select_all);
 		this->SetWidgetDisabledState(WID_NCL_SELECT_UPDATE, !show_select_upgrade);
 		this->SetWidgetDisabledState(WID_NCL_OPEN_URL, this->selected == nullptr || this->selected->url.empty());
-		for (TextfileType tft = TFT_BEGIN; tft < TFT_END; tft++) {
+		for (TextfileType tft = TFT_CONTENT_BEGIN; tft < TFT_CONTENT_END; tft++) {
 			this->SetWidgetDisabledState(WID_NCL_TEXTFILE + tft, this->selected == nullptr || this->selected->state != ContentInfo::ALREADY_HERE || this->selected->GetTextfile(tft) == nullptr);
 		}

--- a/src/network/network_gui.cpp
+++ b/src/network/network_gui.cpp
@@ -19,6 +19,7 @@
 #include "network_content.h"
 #include "network_server.h"
 #include "network_coordinator.h"
+#include "network_survey.h"
 #include "../gui.h"
 #include "network_udp.h"
 #include "../window_func.h"
@@ -38,6 +39,7 @@
 #include "../zoom_func.h"
 #include "../sprite.h"
 #include "../settings_internal.h"
+#include "../textfile_gui.h"

 #include "../widgets/network_widget.h"

@@ -764,9 +766,9 @@ public:
 				break;

 			case WID_NG_MATRIX: { // Show available network games
-				uint id_v = this->vscroll->GetScrolledRowFromWidget(pt.y, this, WID_NG_MATRIX);
-				this->server = (id_v < this->servers.size()) ? this->servers[id_v] : nullptr;
-				this->list_pos = (server == nullptr) ? SLP_INVALID : id_v;
+				auto it = this->vscroll->GetScrolledItemFromWidget(this->servers, pt.y, this, WID_NG_MATRIX);
+				this->server = (it != this->servers.end()) ? *it : nullptr;
+				this->list_pos = (server == nullptr) ? SLP_INVALID : it - this->servers.begin();
 				this->SetDirty();

 				/* FIXME the disabling should go into some InvalidateData, which is called instead of the SetDirty */
@@ -1462,7 +1464,7 @@ public:
 		this->height = d.height + WidgetDimensions::scaled.framerect.Vertical();
 		this->width = d.width + WidgetDimensions::scaled.framerect.Horizontal();
 	}
-	virtual ~ButtonCommon() {}
+	virtual ~ButtonCommon() = default;

 	/**
 	 * OnClick handler for when the button is pressed.
@@ -2448,7 +2450,8 @@ struct NetworkAskRelayWindow : public Window {
 	{
 		if (widget == WID_NAR_TEXT) {
 			*size = GetStringBoundingBox(STR_NETWORK_ASK_RELAY_TEXT);
-			size->height = GetStringHeight(STR_NETWORK_ASK_RELAY_TEXT, size->width - WidgetDimensions::scaled.frametext.Horizontal()) + WidgetDimensions::scaled.frametext.Vertical();
+			size->width += WidgetDimensions::scaled.frametext.Horizontal();
+			size->height += WidgetDimensions::scaled.frametext.Vertical();
 		}
 	}

@@ -2534,3 +2537,119 @@ void ShowNetworkAskRelay(const std::string &server_connection_string, const std:
 	Window *parent = GetMainWindow();
 	new NetworkAskRelayWindow(&_network_ask_relay_desc, parent, server_connection_string, relay_connection_string, token);
 }
+
+/**
+ * Window used for asking if the user wants to participate in the automated survey.
+ */
+struct NetworkAskSurveyWindow : public Window {
+	NetworkAskSurveyWindow(WindowDesc *desc, Window *parent) :
+		Window(desc)
+	{
+		this->parent = parent;
+		this->InitNested(0);
+	}
+
+	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override
+	{
+		if (widget == WID_NAS_TEXT) {
+			*size = GetStringBoundingBox(STR_NETWORK_ASK_SURVEY_TEXT);
+			size->width += WidgetDimensions::scaled.frametext.Horizontal();
+			size->height += WidgetDimensions::scaled.frametext.Vertical();
+		}
+	}
+
+	void DrawWidget(const Rect &r, int widget) const override
+	{
+		if (widget == WID_NAS_TEXT) {
+			DrawStringMultiLine(r.Shrink(WidgetDimensions::scaled.frametext), STR_NETWORK_ASK_SURVEY_TEXT, TC_BLACK, SA_CENTER);
+		}
+	}
+
+	void FindWindowPlacementAndResize(int def_width, int def_height) override
+	{
+		/* Position query window over the calling window, ensuring it's within screen bounds. */
+		this->left = Clamp(parent->left + (parent->width / 2) - (this->width / 2), 0, _screen.width - this->width);
+		this->top = Clamp(parent->top + (parent->height / 2) - (this->height / 2), 0, _screen.height - this->height);
+		this->SetDirty();
+	}
+
+	void OnClick(Point pt, int widget, int click_count) override
+	{
+		switch (widget) {
+			case WID_NAS_PREVIEW:
+				ShowSurveyResultTextfileWindow();
+				break;
+
+			case WID_NAS_LINK:
+				OpenBrowser(NETWORK_SURVEY_DETAILS_LINK.c_str());
+				break;
+
+			case WID_NAS_NO:
+				_settings_client.network.participate_survey = PS_NO;
+				this->Close();
+				break;
+
+			case WID_NAS_YES:
+				_settings_client.network.participate_survey = PS_YES;
+				this->Close();
+				break;
+		}
+	}
+};
+
+static const NWidgetPart _nested_network_ask_survey_widgets[] = {
+	NWidget(NWID_HORIZONTAL),
+		NWidget(WWT_CLOSEBOX, COLOUR_GREY),
+		NWidget(WWT_CAPTION, COLOUR_GREY, WID_NAS_CAPTION), SetDataTip(STR_NETWORK_ASK_SURVEY_CAPTION, STR_NULL),
+	EndContainer(),
+	NWidget(WWT_PANEL, COLOUR_GREY), SetPIP(0, 4, 8),
+		NWidget(WWT_TEXT, COLOUR_GREY, WID_NAS_TEXT), SetAlignment(SA_HOR_CENTER), SetFill(1, 1),
+		NWidget(NWID_HORIZONTAL, NC_EQUALSIZE), SetPIP(10, 15, 10),
+			NWidget(WWT_PUSHTXTBTN, COLOUR_WHITE, WID_NAS_PREVIEW), SetMinimalSize(71, 12), SetFill(1, 1), SetDataTip(STR_NETWORK_ASK_SURVEY_PREVIEW, STR_NULL),
+			NWidget(WWT_PUSHTXTBTN, COLOUR_WHITE, WID_NAS_LINK), SetMinimalSize(71, 12), SetFill(1, 1), SetDataTip(STR_NETWORK_ASK_SURVEY_LINK, STR_NULL),
+		EndContainer(),
+		NWidget(NWID_HORIZONTAL, NC_EQUALSIZE), SetPIP(10, 15, 10),
+			NWidget(WWT_PUSHTXTBTN, COLOUR_GREY, WID_NAS_NO), SetMinimalSize(71, 12), SetFill(1, 1), SetDataTip(STR_NETWORK_ASK_SURVEY_NO, STR_NULL),
+			NWidget(WWT_PUSHTXTBTN, COLOUR_GREY, WID_NAS_YES), SetMinimalSize(71, 12), SetFill(1, 1), SetDataTip(STR_NETWORK_ASK_SURVEY_YES, STR_NULL),
+		EndContainer(),
+	EndContainer(),
+};
+
+static WindowDesc _network_ask_survey_desc(
+	WDP_CENTER, nullptr, 0, 0,
+	WC_NETWORK_ASK_SURVEY, WC_NONE,
+	WDF_MODAL,
+	_nested_network_ask_survey_widgets, lengthof(_nested_network_ask_survey_widgets)
+);
+
+/**
+ * Show a modal confirmation window with "no" / "preview" / "yes" buttons.
+ */
+void ShowNetworkAskSurvey()
+{
+	/* If we can't send a survey, don't ask the question. */
+	if constexpr (!NetworkSurveyHandler::IsSurveyPossible()) return;
+
+	CloseWindowByClass(WC_NETWORK_ASK_SURVEY);
+
+	Window *parent = GetMainWindow();
+	new NetworkAskSurveyWindow(&_network_ask_survey_desc, parent);
+}
+
+/** Window for displaying the textfile of a survey result. */
+struct SurveyResultTextfileWindow : public TextfileWindow {
+	const GRFConfig *grf_config; ///< View the textfile of this GRFConfig.
+
+	SurveyResultTextfileWindow(TextfileType file_type) : TextfileWindow(file_type)
+	{
+		auto result = _survey.CreatePayload(NetworkSurveyHandler::Reason::PREVIEW, true);
+		this->LoadText(result);
+		this->InvalidateData();
+	}
+};
+
+void ShowSurveyResultTextfileWindow()
+{
+	CloseWindowById(WC_TEXTFILE, TFT_SURVEY_RESULT);
+	new SurveyResultTextfileWindow(TFT_SURVEY_RESULT);
+}
--- a/src/network/network_gui.h
+++ b/src/network/network_gui.h
@@ -25,7 +25,8 @@ void ShowNetworkGameWindow();
 void ShowClientList();
 void ShowNetworkCompanyPasswordWindow(Window *parent);
 void ShowNetworkAskRelay(const std::string &server_connection_string, const std::string &relay_connection_string, const std::string &token);
-
+void ShowNetworkAskSurvey();
+void ShowSurveyResultTextfileWindow();

 /** Company information stored at the client side */
 struct NetworkCompanyInfo : NetworkCompanyStats {
--- a/src/network/network_survey.cpp
+++ b/src/network/network_survey.cpp
@@ -0,0 +1,366 @@
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD 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, version 2.
+ * OpenTTD 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 OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file network_survey.cpp Opt-in survey part of the network protocol. */
+
+#include "../stdafx.h"
+#include "network_survey.h"
+#include "network.h"
+#include "network_internal.h"
+#include "../company_base.h"
+#include "../debug.h"
+#include "../debug_fmt.h"
+#include "../rev.h"
+#include "../settings_type.h"
+#include "../settings_internal.h"
+#include "../timer/timer_game_tick.h"
+#include "../sl/saveload.h"
+#include "../date_func.h"
+
+#include "../currency.h"
+#include "../fontcache.h"
+#include "../language.h"
+
+#include "../ai/ai_info.hpp"
+#include "../game/game.hpp"
+#include "../game/game_info.hpp"
+
+#include "../music/music_driver.hpp"
+#include "../sound/sound_driver.hpp"
+#include "../video/video_driver.hpp"
+
+#include "../base_media_base.h"
+#include "../blitter/factory.hpp"
+
+#ifdef WITH_NLOHMANN_JSON
+#include <nlohmann/json.hpp>
+#endif /* WITH_NLOHMANN_JSON */
+
+#include "../safeguards.h"
+
+extern std::string _savegame_id;
+
+NetworkSurveyHandler _survey = {};
+
+#ifdef WITH_NLOHMANN_JSON
+
+NLOHMANN_JSON_SERIALIZE_ENUM(NetworkSurveyHandler::Reason, {
+	{NetworkSurveyHandler::Reason::PREVIEW, "preview"},
+	{NetworkSurveyHandler::Reason::LEAVE, "leave"},
+	{NetworkSurveyHandler::Reason::EXIT, "exit"},
+	{NetworkSurveyHandler::Reason::CRASH, "crash"},
+})
+
+NLOHMANN_JSON_SERIALIZE_ENUM(GRFStatus, {
+	{GRFStatus::GCS_UNKNOWN, "unknown"},
+	{GRFStatus::GCS_DISABLED, "disabled"},
+	{GRFStatus::GCS_NOT_FOUND, "not found"},
+	{GRFStatus::GCS_INITIALISED, "initialised"},
+	{GRFStatus::GCS_ACTIVATED, "activated"},
+})
+
+static const std::string _vehicle_type_to_string[] = {
+	"train",
+	"roadveh",
+	"ship",
+	"aircraft",
+};
+
+/* Defined in one of the os/ survey files. */
+extern void SurveyOS(nlohmann::json &json);
+
+/**
+ * Convert a settings table to JSON.
+ *
+ * @param survey The JSON object.
+ * @param table The settings table to convert.
+ * @param object The object to get the settings from.
+ */
+static void SurveySettingsTable(nlohmann::json &survey, const SettingTable &table, void *object)
+{
+	char buf[512];
+	for (auto &sd : table) {
+		/* Skip any old settings we no longer save/load. */
+		if (!SlIsObjectCurrentlyValid(sd->save.version_from, sd->save.version_to, sd->save.ext_feature_test)) continue;
+
+		auto name = sd->name;
+		sd->FormatValue(buf, lastof(buf), object);
+
+		survey[name] = buf;
+	}
+}
+
+/**
+ * Convert settings to JSON.
+ *
+ * @param survey The JSON object.
+ */
+static void SurveySettings(nlohmann::json &survey)
+{
+	IterateSettingsTables([&](const SettingTable &table, void *object) {
+		SurveySettingsTable(survey, table, object);
+	});
+}
+
+/**
+ * Convert generic OpenTTD information to JSON.
+ *
+ * @param survey The JSON object.
+ */
+static void SurveyOpenTTD(nlohmann::json &survey)
+{
+	survey["version"] = std::string(_openttd_revision);
+	survey["newgrf_version"] = _openttd_newgrf_version;
+	survey["build_date"] = std::string(_openttd_build_date);
+	survey["bits"] =
+#ifdef POINTER_IS_64BIT
+			64
+#else
+			32
+#endif
+		;
+	survey["endian"] =
+#if (TTD_ENDIAN == TTD_LITTLE_ENDIAN)
+			"little"
+#else
+			"big"
+#endif
+		;
+	survey["dedicated_build"] =
+#ifdef DEDICATED
+			"yes"
+#else
+			"no"
+#endif
+		;
+}
+
+/**
+ * Convert generic game information to JSON.
+ *
+ * @param survey The JSON object.
+ */
+static void SurveyConfiguration(nlohmann::json &survey)
+{
+	survey["network"] = _networking ? (_network_server ? "server" : "client") : "no";
+	if (_current_language != nullptr) {
+		std::string_view language_basename(_current_language->file);
+		auto e = language_basename.rfind(PATHSEPCHAR);
+		if (e != std::string::npos) {
+			language_basename = language_basename.substr(e + 1);
+		}
+
+		survey["language"]["filename"] = language_basename;
+		survey["language"]["name"] = _current_language->name;
+		survey["language"]["isocode"] = _current_language->isocode;
+	}
+	if (BlitterFactory::GetCurrentBlitter() != nullptr) {
+		survey["blitter"] = BlitterFactory::GetCurrentBlitter()->GetName();
+	}
+	if (MusicDriver::GetInstance() != nullptr) {
+		survey["music_driver"] = MusicDriver::GetInstance()->GetName();
+	}
+	if (SoundDriver::GetInstance() != nullptr) {
+		survey["sound_driver"] = SoundDriver::GetInstance()->GetName();
+	}
+	if (VideoDriver::GetInstance() != nullptr) {
+		survey["video_driver"] = VideoDriver::GetInstance()->GetName();
+		survey["video_info"] = VideoDriver::GetInstance()->GetInfoString();
+	}
+	if (BaseGraphics::GetUsedSet() != nullptr) {
+		survey["graphics_set"] = fmt::format("{}.{}", BaseGraphics::GetUsedSet()->name, BaseGraphics::GetUsedSet()->version);
+	}
+	if (BaseMusic::GetUsedSet() != nullptr) {
+		survey["music_set"] = fmt::format("{}.{}", BaseMusic::GetUsedSet()->name, BaseMusic::GetUsedSet()->version);
+	}
+	if (BaseSounds::GetUsedSet() != nullptr) {
+		survey["sound_set"] = fmt::format("{}.{}", BaseSounds::GetUsedSet()->name, BaseSounds::GetUsedSet()->version);
+	}
+}
+
+/**
+ * Convert font information to JSON.
+ *
+ * @param survey The JSON object.
+ */
+static void SurveyFont(nlohmann::json &survey)
+{
+	survey["small"] = FontCache::Get(FS_SMALL)->GetFontName();
+	survey["medium"] = FontCache::Get(FS_NORMAL)->GetFontName();
+	survey["large"] = FontCache::Get(FS_LARGE)->GetFontName();
+	survey["mono"] = FontCache::Get(FS_MONO)->GetFontName();
+}
+
+/**
+ * Convert company information to JSON.
+ *
+ * @param survey The JSON object.
+ */
+static void SurveyCompanies(nlohmann::json &survey)
+{
+	for (const Company *c : Company::Iterate()) {
+		auto &company = survey[std::to_string(c->index)];
+		if (c->ai_info == nullptr) {
+			company["type"] = "human";
+		} else {
+			company["type"] = "ai";
+			company["script"] = fmt::format("{}.{}", c->ai_info->GetName(), c->ai_info->GetVersion());
+		}
+
+		for (VehicleType type = VEH_BEGIN; type < VEH_COMPANY_END; type++) {
+			uint amount = c->group_all[type].num_vehicle;
+			company["vehicles"][_vehicle_type_to_string[type]] = amount;
+		}
+
+		company["infrastructure"]["road"] = c->infrastructure.GetRoadTotal();
+		company["infrastructure"]["tram"] = c->infrastructure.GetTramTotal();
+		company["infrastructure"]["rail"] = c->infrastructure.GetRailTotal();
+		company["infrastructure"]["signal"] = c->infrastructure.signal;
+		company["infrastructure"]["water"] = c->infrastructure.water;
+		company["infrastructure"]["station"] = c->infrastructure.station;
+		company["infrastructure"]["airport"] = c->infrastructure.airport;
+	}
+}
+
+/**
+ * Convert GRF information to JSON.
+ *
+ * @param survey The JSON object.
+ */
+static void SurveyGrfs(nlohmann::json &survey)
+{
+	for (GRFConfig *c = _grfconfig; c != nullptr; c = c->next) {
+		auto grfid = fmt::format("{:08x}", BSWAP32(c->ident.grfid));
+		auto &grf = survey[grfid];
+
+		grf["md5sum"] = BytesToHexString(c->ident.md5sum, 16);
+		grf["status"] = c->status;
+
+		if ((c->palette & GRFP_GRF_MASK) == GRFP_GRF_UNSET) grf["palette"] = "unset";
+		if ((c->palette & GRFP_GRF_MASK) == GRFP_GRF_DOS) grf["palette"] = "dos";
+		if ((c->palette & GRFP_GRF_MASK) == GRFP_GRF_WINDOWS) grf["palette"] = "windows";
+		if ((c->palette & GRFP_GRF_MASK) == GRFP_GRF_ANY) grf["palette"] = "any";
+
+		if ((c->palette & GRFP_BLT_MASK) == GRFP_BLT_UNSET) grf["blitter"] = "unset";
+		if ((c->palette & GRFP_BLT_MASK) == GRFP_BLT_32BPP) grf["blitter"] = "32bpp";
+
+		grf["is_static"] = HasBit(c->flags, GCF_STATIC);
+
+		std::vector<uint32> parameters;
+		for (int i = 0; i < c->num_params; i++) {
+			parameters.push_back(c->param[i]);
+		}
+		grf["parameters"] = parameters;
+	}
+}
+
+/**
+ * Convert game-script information to JSON.
+ *
+ * @param survey The JSON object.
+ */
+static void SurveyGameScript(nlohmann::json &survey)
+{
+	if (Game::GetInfo() == nullptr) return;
+
+	survey = fmt::format("{}.{}", Game::GetInfo()->GetName(), Game::GetInfo()->GetVersion());
+}
+
+#endif /* WITH_NLOHMANN_JSON */
+
+/**
+ * Create the payload for the survey.
+ *
+ * @param reason The reason for sending the survey.
+ * @param for_preview Whether the payload is meant for preview. This indents the result, and filters out the id/key.
+ * @return std::string The JSON payload as string for the survey.
+ */
+std::string NetworkSurveyHandler::CreatePayload(Reason reason, bool for_preview)
+{
+#ifndef WITH_NLOHMANN_JSON
+	return "";
+#else
+	nlohmann::json survey;
+
+	survey["schema"] = NETWORK_SURVEY_VERSION;
+	survey["reason"] = reason;
+	survey["id"] = _savegame_id;
+
+#ifdef SURVEY_KEY
+	/* We censor the key to avoid people trying to be "clever" and use it to send their own surveys. */
+	survey["key"] = for_preview ? "(redacted)" : SURVEY_KEY;
+#else
+	survey["key"] = "";
+#endif
+
+	{
+		auto &info = survey["info"];
+		SurveyOS(info["os"]);
+		info["os"]["hardware_concurrency"] = std::thread::hardware_concurrency();
+
+		SurveyOpenTTD(info["openttd"]);
+		SurveyConfiguration(info["configuration"]);
+		SurveyFont(info["font"]);
+	}
+
+	{
+		auto &game = survey["game"];
+		game["ticks"] = _scaled_tick_counter;
+		game["time"] = std::chrono::duration_cast<std::chrono::seconds>(std::chrono::steady_clock::now() - _switch_mode_time).count();
+		SurveyCompanies(game["companies"]);
+		SurveySettings(game["settings"]);
+		SurveyGrfs(game["grfs"]);
+		SurveyGameScript(game["game_script"]);
+	}
+
+	/* For preview, we indent with 4 whitespaces to make things more readable. */
+	int indent = for_preview ? 4 : -1;
+	return survey.dump(indent);
+#endif /* WITH_NLOHMANN_JSON */
+}
+
+/**
+ * Transmit the survey.
+ *
+ * @param reason The reason for sending the survey.
+ * @param blocking Whether to block until the survey is sent.
+ */
+void NetworkSurveyHandler::Transmit(Reason reason, bool blocking)
+{
+	if constexpr (!NetworkSurveyHandler::IsSurveyPossible()) {
+		Debug(net, 4, "Survey: not possible to send survey; most likely due to missing JSON library at compile-time");
+		return;
+	}
+
+	if (_settings_client.network.participate_survey != PS_YES) {
+		Debug(net, 5, "Survey: user is not participating in survey; skipping survey");
+		return;
+	}
+
+	Debug(net, 1, "Survey: sending survey results");
+	NetworkHTTPSocketHandler::Connect(NetworkSurveyUriString(), this, this->CreatePayload(reason));
+
+	if (blocking) {
+		std::unique_lock<std::mutex> lock(this->mutex);
+		/* Block no longer than 2 seconds. If we failed to send the survey in that time, so be it. */
+		this->loaded.wait_for(lock, std::chrono::seconds(2));
+	}
+}
+
+void NetworkSurveyHandler::OnFailure()
+{
+	Debug(net, 1, "Survey: failed to send survey results");
+	this->loaded.notify_all();
+}
+
+void NetworkSurveyHandler::OnReceiveData(const char *data, size_t length)
+{
+	if (data == nullptr) {
+		Debug(net, 1, "Survey: survey results sent");
+		this->loaded.notify_all();
+	}
+}
--- a/src/network/network_survey.h
+++ b/src/network/network_survey.h
@@ -0,0 +1,54 @@
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD 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, version 2.
+ * OpenTTD 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 OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file network_survey.h Part of the network protocol handling opt-in survey. */
+
+#ifndef NETWORK_SURVEY_H
+#define NETWORK_SURVEY_H
+
+#include <condition_variable>
+#include <mutex>
+#include "core/http.h"
+
+/**
+ * Socket handler for the survey connection
+ */
+class NetworkSurveyHandler : public HTTPCallback {
+protected:
+	void OnFailure() override;
+	void OnReceiveData(const char *data, size_t length) override;
+	bool IsCancelled() const override { return false; }
+
+public:
+	enum class Reason {
+		PREVIEW, ///< User is previewing the survey result.
+		LEAVE, ///< User is leaving the game (but not exiting the application).
+		EXIT, ///< User is exiting the application.
+		CRASH, ///< Game crashed.
+	};
+
+	void Transmit(Reason reason, bool blocking = false);
+	std::string CreatePayload(Reason reason, bool for_preview = false);
+
+	constexpr static bool IsSurveyPossible()
+	{
+#ifndef WITH_NLOHMANN_JSON
+		/* Without JSON library, we cannot send a payload; so we disable the survey. */
+		return false;
+#else
+		return true;
+#endif /* WITH_NLOHMANN_JSON */
+	}
+
+private:
+	std::mutex mutex; ///< Mutex for the condition variable.
+	std::condition_variable loaded; ///< Condition variable to wait for the survey to be sent.
+};
+
+extern NetworkSurveyHandler _survey;
+
+#endif /* NETWORK_SURVEY_H */
--- a/src/network/network_udp.cpp
+++ b/src/network/network_udp.cpp
@@ -82,7 +82,7 @@ public:
 	 * @param addresses The addresses to bind on.
 	 */
 	ServerNetworkUDPSocketHandler(NetworkAddressList *addresses) : NetworkUDPSocketHandler(addresses) {}
-	virtual ~ServerNetworkUDPSocketHandler() {}
+	virtual ~ServerNetworkUDPSocketHandler() = default;
 };

 void ServerNetworkUDPSocketHandler::Receive_CLIENT_FIND_SERVER(Packet *p, NetworkAddress *client_addr)
@@ -117,7 +117,7 @@ protected:
 	void Receive_SERVER_RESPONSE(Packet *p, NetworkAddress *client_addr) override;
 	void Receive_EX_SERVER_RESPONSE(Packet *p, NetworkAddress *client_addr) override;
 public:
-	virtual ~ClientNetworkUDPSocketHandler() {}
+	virtual ~ClientNetworkUDPSocketHandler() = default;
 };

 void ClientNetworkUDPSocketHandler::Receive_SERVER_RESPONSE(Packet *p, NetworkAddress *client_addr)