From 22f5b00fce2df3f58ed0aab94ff12ddc69c7c5da Mon Sep 17 00:00:00 2001
From: elexis <elexis@wildfiregames.com>
Date: Thu, 4 Feb 2016 17:14:46 +0000
Subject: [PATCH] Implement network-warnings, fixes #3264.

Shows a notification if the local client or other players connections
timeout or have bad latency.

This was SVN commit r17730.
---
 binaries/data/config/default.cfg              |   1 +
 .../gui/common/functions_global_object.js     |  45 +++++++-
 .../data/mods/public/gui/common/global.xml    |  18 +++
 .../data/mods/public/gui/common/network.js    | 104 +++++++++++++++++
 .../mods/public/gui/gamesetup/gamesetup.js    |   5 +
 .../mods/public/gui/gamesetup/gamesetup.xml   |   1 +
 .../mods/public/gui/gamesetup/gamesetup_mp.js |   8 +-
 .../data/mods/public/gui/options/options.json |   6 +
 .../data/mods/public/gui/session/messages.js  |   1 +
 .../data/mods/public/gui/session/session.js   |   2 +
 source/gui/scripting/ScriptFunctions.cpp      |  12 ++
 source/network/NetClient.cpp                  | 108 +++++++++++++++++-
 source/network/NetClient.h                    |  12 +-
 source/network/NetMessage.cpp                 |  10 +-
 source/network/NetMessages.h                  |  19 ++-
 source/network/NetServer.cpp                  |  54 ++++++++-
 source/network/NetServer.h                    |  11 +-
 source/network/NetSession.cpp                 |  34 ++++++
 source/network/NetSession.h                   |  27 ++++-
 source/network/NetTurnManager.cpp             |   4 +-
 source/network/NetTurnManager.h               |   5 +-
 21 files changed, 468 insertions(+), 19 deletions(-)

diff --git a/binaries/data/config/default.cfg b/binaries/data/config/default.cfg
index cefb61b2e3..e1c48e7df4 100644
--- a/binaries/data/config/default.cfg
+++ b/binaries/data/config/default.cfg
@@ -352,6 +352,7 @@ enabledmods = "mod public"
 [overlay]
 fps = "false"                     ; Show frames per second in top right corner
 realtime = "false"                ; Show current system time in top right corner
+netwarnings = "true"              ; Show warnings if the network connection is bad
 
 [profiler2]
 autoenable = false                ; Enable HTTP server output at startup (default off for security/performance)
diff --git a/binaries/data/mods/public/gui/common/functions_global_object.js b/binaries/data/mods/public/gui/common/functions_global_object.js
index 428a756818..4fc6144a26 100644
--- a/binaries/data/mods/public/gui/common/functions_global_object.js
+++ b/binaries/data/mods/public/gui/common/functions_global_object.js
@@ -1,7 +1,6 @@
-/*
-	DESCRIPTION	: Contains global GUI functions, which will later be accessible from every GUI script/file.
-	NOTES		: So far, only the message box-related functions are implemented.
-*/
+/**
+ * Contains global GUI functions accessible from every GUI script/file.
+ */
 
 // *******************************************
 // messageBox
@@ -139,4 +138,42 @@ function updateCounters()
 	var dataCounter = Engine.GetGUIObjectByName("dataCounter");
 	dataCounter.caption = caption;
 	dataCounter.size = sprintf("100%%-100 40 100%%-5 %(bottom)s", { bottom: 40 + 14 * linesCount });
+	dataCounter.hidden = linesCount == 0;
+}
+
+/**
+ * Update the overlay with the most recent network warning of each client.
+ */
+function displayGamestateNotifications()
+{
+	let messages = [];
+	let maxTextWidth = 0;
+
+	// TODO: Players who paused the game should be added here
+
+	// Add network warnings
+	if (Engine.ConfigDB_GetValue("user", "overlay.netwarnings") == "true")
+	{
+		let netwarnings = getNetworkWarnings();
+		messages = messages.concat(netwarnings.messages);
+		maxTextWidth = Math.max(maxTextWidth, netwarnings.maxTextWidth);
+	}
+
+	// Resize textbox
+	let width = maxTextWidth + 20;
+	let height = 14 * messages.length;
+
+	// Position left of the dataCounter
+	let top = "40";
+	let right = Engine.GetGUIObjectByName("dataCounter").hidden ? "100%-15" : "100%-110";
+
+	let bottom = top + "+" + height;
+	let left = right + "-" + width;
+
+	let gameStateNotifications = Engine.GetGUIObjectByName("gameStateNotifications");
+	gameStateNotifications.caption = messages.join("\n");
+	gameStateNotifications.hidden = !messages.length;
+	gameStateNotifications.size = left + " " + top + " " + right + " " + bottom;
+
+	setTimeout(displayGamestateNotifications, 1000);
 }
diff --git a/binaries/data/mods/public/gui/common/global.xml b/binaries/data/mods/public/gui/common/global.xml
index 04fc871606..61632b4748 100644
--- a/binaries/data/mods/public/gui/common/global.xml
+++ b/binaries/data/mods/public/gui/common/global.xml
@@ -12,6 +12,24 @@
 
 	<object>
 
+		<!--
+		==========================================
+		- GAMESTATE NOTIFICATIONS
+		==========================================
+		-->
+		<object name="gameStateNotifications"
+			type="text"
+			ghost="true"
+			z="199"
+			size="100%-110 40 100%-110 40"
+			font="mono-stroke-10"
+			textcolor="255 219 77"
+			text_align="center"
+			text_valign="top"
+			sprite="color: 0 0 0 100"
+			>
+		</object>
+
 		<!--
 		==========================================
 		- FPS & REAL TIME & GAME TIME COUNTER
diff --git a/binaries/data/mods/public/gui/common/network.js b/binaries/data/mods/public/gui/common/network.js
index 7ba591125f..cc3fc0412a 100644
--- a/binaries/data/mods/public/gui/common/network.js
+++ b/binaries/data/mods/public/gui/common/network.js
@@ -1,3 +1,41 @@
+/**
+ * Number of milliseconds to display network warnings.
+ */
+const g_NetworkWarningTimeout = 3000;
+
+/**
+ * Currently displayed network warnings. At most one message per user.
+ */
+var g_NetworkWarnings = {};
+
+/**
+ * Message-types to be displayed.
+ */
+var g_NetworkWarningTexts = {
+
+	"server-timeout": (msg, username) =>
+		sprintf(translate("Losing connection to server (%(seconds)s)"), {
+			"seconds": Math.ceil(msg.lastReceivedTime / 1000)
+		}),
+
+	"client-timeout": (msg, username) =>
+		sprintf(translate("%(player)s losing connection (%(seconds)s)"), {
+			"player": username,
+			"seconds": Math.ceil(msg.lastReceivedTime / 1000)
+		}),
+
+	"server-latency": (msg, username) =>
+		sprintf(translate("Bad connection to server (%(milliseconds)sms)"), {
+			"milliseconds": msg.meanRTT
+		}),
+
+	"client-latency": (msg, username) =>
+		sprintf(translate("Bad connection to %(player)s (%(milliseconds)sms)"), {
+			"player": username,
+			"milliseconds": msg.meanRTT
+		})
+};
+
 var g_NetworkCommands = {
 	"/kick": argument => kickPlayer(argument, false),
 	"/ban": argument => kickPlayer(argument, true),
@@ -94,3 +132,69 @@ function executeNetworkCommand(input)
 
 	return !!g_NetworkCommands[command];
 }
+
+/**
+ * Remember this warning for a few seconds.
+ * Overwrite previous warnings for this user.
+ *
+ * @param msg - GUI message sent by NetServer or NetClient
+ */
+function addNetworkWarning(msg)
+{
+	if (!g_NetworkWarningTexts[msg.warntype])
+	{
+		warn("Unknown network warning type received: " + uneval(msg));
+		return;
+	}
+
+	if (Engine.ConfigDB_GetValue("user", "overlay.netwarnings") != "true")
+		return;
+
+	g_NetworkWarnings[msg.guid || "server"] = {
+		"added": Date.now(),
+		"msg": msg
+	};
+}
+
+/**
+ * Colorizes and concatenates all network warnings.
+ * Returns text and textWidth.
+ */
+function getNetworkWarnings()
+{
+	// Remove outdated messages
+	for (let guid in g_NetworkWarnings)
+	{
+		if (Date.now() > g_NetworkWarnings[guid].added + g_NetworkWarningTimeout)
+			delete g_NetworkWarnings[guid];
+
+		if (guid != "server" && !g_PlayerAssignments[guid])
+			delete g_NetworkWarnings[guid];
+	}
+
+	// Show local messages first
+	let guids = Object.keys(g_NetworkWarnings).sort(guid => guid != "server");
+
+	let font = Engine.GetGUIObjectByName("gameStateNotifications").font;
+
+	let messages = [];
+	let maxTextWidth = 0;
+
+	for (let guid of guids)
+	{
+		let msg = g_NetworkWarnings[guid].msg;
+
+		// Add formatted text
+		messages.push(g_NetworkWarningTexts[msg.warntype](msg, colorizePlayernameByGUID(guid)));
+
+		// Add width of unformatted text
+		let username = guid != "server" && g_PlayerAssignments[guid].name;
+		let textWidth = Engine.GetTextWidth(font, g_NetworkWarningTexts[msg.warntype](msg, username));
+		maxTextWidth = Math.max(textWidth, maxTextWidth);
+	}
+
+	return {
+		"messages": messages,
+		"maxTextWidth": maxTextWidth
+	};
+}
diff --git a/binaries/data/mods/public/gui/gamesetup/gamesetup.js b/binaries/data/mods/public/gui/gamesetup/gamesetup.js
index a9e703e35a..e0b934cecd 100644
--- a/binaries/data/mods/public/gui/gamesetup/gamesetup.js
+++ b/binaries/data/mods/public/gui/gamesetup/gamesetup.js
@@ -28,6 +28,7 @@ const g_MapPath = {
  */
 const g_NetMessageTypes = {
 	"netstatus": msg => handleNetStatusMessage(msg),
+	"netwarn": msg => addNetworkWarning(msg),
 	"gamesetup": msg => handleGamesetupMessage(msg),
 	"players": msg => handlePlayerAssignmentMessage(msg),
 	"ready": msg => handleReadyMessage(msg),
@@ -211,6 +212,8 @@ function init(attribs)
 	g_DefaultPlayerData.shift();
 	for (let i in g_DefaultPlayerData)
 		g_DefaultPlayerData[i].Civ = "random";
+
+	setTimeout(displayGamestateNotifications, 1000);
 }
 
 /**
@@ -946,6 +949,8 @@ function onTick()
 				error("Unrecognised net message type " + message.type);
 		}
 	}
+
+	updateTimers();
 }
 
 /**
diff --git a/binaries/data/mods/public/gui/gamesetup/gamesetup.xml b/binaries/data/mods/public/gui/gamesetup/gamesetup.xml
index 7e8c88849a..6fd27e7e5d 100644
--- a/binaries/data/mods/public/gui/gamesetup/gamesetup.xml
+++ b/binaries/data/mods/public/gui/gamesetup/gamesetup.xml
@@ -8,6 +8,7 @@
 	<script file="gui/common/functions_utility.js"/>
 	<script file="gui/common/network.js"/>
 	<script file="gui/common/settings.js"/>
+	<script file="gui/common/timer.js"/>
 
 	<!-- After settings.js, which defines g_Settings -->
 	<script file="gui/gamesetup/gamesetup.js"/>
diff --git a/binaries/data/mods/public/gui/gamesetup/gamesetup_mp.js b/binaries/data/mods/public/gui/gamesetup/gamesetup_mp.js
index a143b9c91a..faefc71b6b 100644
--- a/binaries/data/mods/public/gui/gamesetup/gamesetup_mp.js
+++ b/binaries/data/mods/public/gui/gamesetup/gamesetup_mp.js
@@ -126,7 +126,9 @@ function pollAndHandleNetworkClient()
 				break;
 
 			case "chat":
-				// Ignore, since we have nowhere to display chat messages
+				break;
+
+			case "netwarn":
 				break;
 
 			default:
@@ -169,6 +171,10 @@ function pollAndHandleNetworkClient()
 					break;
 				}
 				break;
+
+			case "netwarn":
+				break;
+
 			default:
 				error(sprintf("Unrecognised net message type %(messageType)s", { messageType: message.type }));
 				break;
diff --git a/binaries/data/mods/public/gui/options/options.json b/binaries/data/mods/public/gui/options/options.json
index 87a0463232..57b04a57b5 100644
--- a/binaries/data/mods/public/gui/options/options.json
+++ b/binaries/data/mods/public/gui/options/options.json
@@ -25,6 +25,12 @@
 			"tooltip": "Show detailed tooltips for trainable units in unit-producing buildings.",
 			"parameters": { "config": "showdetailedtooltips" }
 		},
+		{
+			"type": "boolean",
+			"label": "Network Warnings",
+			"tooltip": "Show which player has a bad connection in multiplayer games.",
+			"parameters": { "config": "overlay.netwarnings" }
+		},
 		{
 			"type": "boolean",
 			"label": "FPS Overlay",
diff --git a/binaries/data/mods/public/gui/session/messages.js b/binaries/data/mods/public/gui/session/messages.js
index 1172acdf13..71962f7688 100644
--- a/binaries/data/mods/public/gui/session/messages.js
+++ b/binaries/data/mods/public/gui/session/messages.js
@@ -29,6 +29,7 @@ var g_ChatTimers = [];
  */
 var g_NetMessageTypes = {
 	"netstatus": msg => handleNetStatusMessage(msg),
+	"netwarn": msg => addNetworkWarning(msg),
 	"players": msg => handlePlayerAssignmentsMessage(msg),
 	"rejoined": msg => addChatMessage({ "type": "rejoined", "guid": msg.guid }),
 	"kicked": msg => addChatMessage({ "type": "system", "text": sprintf(translate("%(username)s has been kicked"), { "username": msg.username }) }),
diff --git a/binaries/data/mods/public/gui/session/session.js b/binaries/data/mods/public/gui/session/session.js
index 0a006afb08..03c799300c 100644
--- a/binaries/data/mods/public/gui/session/session.js
+++ b/binaries/data/mods/public/gui/session/session.js
@@ -269,6 +269,8 @@ function init(initData, hotloadData)
 
 	onSimulationUpdate();
 
+	setTimeout(displayGamestateNotifications, 1000);
+
 	// Report the performance after 5 seconds (when we're still near
 	// the initial camera view) and a minute (when the profiler will
 	// have settled down if framerates as very low), to give some
diff --git a/source/gui/scripting/ScriptFunctions.cpp b/source/gui/scripting/ScriptFunctions.cpp
index e6c2c656c9..770862fb37 100644
--- a/source/gui/scripting/ScriptFunctions.cpp
+++ b/source/gui/scripting/ScriptFunctions.cpp
@@ -20,6 +20,7 @@
 #include "scriptinterface/ScriptInterface.h"
 
 #include "graphics/Camera.h"
+#include "graphics/FontMetrics.h"
 #include "graphics/GameView.h"
 #include "graphics/MapReader.h"
 #include "graphics/scripting/JSInterface_GameView.h"
@@ -875,6 +876,16 @@ CParamNode GetTemplate(ScriptInterface::CxPrivate* UNUSED(pCxPrivate), const std
 	return g_GUI->GetTemplate(templateName);
 }
 
+int GetTextWidth(ScriptInterface::CxPrivate* UNUSED(pCxPrivate), const CStr& fontName, const CStrW& text)
+{
+	int width = 0;
+	int height = 0;
+	CStrIntern _fontName(fontName);
+	CFontMetrics fontMetrics(_fontName);
+	fontMetrics.CalculateStringSize(text.c_str(), width, height);
+	return width;
+}
+
 //-----------------------------------------------------------------------------
 // Timer
 //-----------------------------------------------------------------------------
@@ -1049,6 +1060,7 @@ void GuiScriptingInit(ScriptInterface& scriptInterface)
 	scriptInterface.RegisterFunction<void, std::wstring, JS::HandleValue, &WriteJSONFile>("WriteJSONFile");
 	scriptInterface.RegisterFunction<bool, std::string, &TemplateExists>("TemplateExists");
 	scriptInterface.RegisterFunction<CParamNode, std::string, &GetTemplate>("GetTemplate");
+	scriptInterface.RegisterFunction<int, CStr, CStrW, &GetTextWidth>("GetTextWidth");
 
 	// User report functions
 	scriptInterface.RegisterFunction<bool, &IsUserReportEnabled>("IsUserReportEnabled");
diff --git a/source/network/NetClient.cpp b/source/network/NetClient.cpp
index ca8f8efbee..9b5bb607fb 100644
--- a/source/network/NetClient.cpp
+++ b/source/network/NetClient.cpp
@@ -1,4 +1,4 @@
-/* Copyright (C) 2015 Wildfire Games.
+/* Copyright (C) 2016 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -70,7 +70,8 @@ CNetClient::CNetClient(CGame* game) :
 	m_Session(NULL),
 	m_UserName(L"anonymous"),
 	m_GUID(ps_generate_guid()), m_HostID((u32)-1), m_ClientTurnManager(NULL), m_Game(game),
-	m_GameAttributes(game->GetSimulation2()->GetScriptInterface().GetContext())
+	m_GameAttributes(game->GetSimulation2()->GetScriptInterface().GetContext()),
+	m_LastConnectionCheck(0)
 {
 	m_Game->SetTurnManager(NULL); // delete the old local turn manager so we don't accidentally use it
 
@@ -94,12 +95,16 @@ CNetClient::CNetClient(CGame* game) :
 	AddTransition(NCS_PREGAME, (uint)NMT_GAME_SETUP, NCS_PREGAME, (void*)&OnGameSetup, context);
 	AddTransition(NCS_PREGAME, (uint)NMT_PLAYER_ASSIGNMENT, NCS_PREGAME, (void*)&OnPlayerAssignment, context);
 	AddTransition(NCS_PREGAME, (uint)NMT_KICKED, NCS_PREGAME, (void*)&OnKicked, context);
+	AddTransition(NCS_PREGAME, (uint)NMT_CLIENT_TIMEOUT, NCS_PREGAME, (void*)&OnClientTimeout, context);
+	AddTransition(NCS_PREGAME, (uint)NMT_CLIENT_PERFORMANCE, NCS_PREGAME, (void*)&OnClientPerformance, context);
 	AddTransition(NCS_PREGAME, (uint)NMT_GAME_START, NCS_LOADING, (void*)&OnGameStart, context);
 	AddTransition(NCS_PREGAME, (uint)NMT_JOIN_SYNC_START, NCS_JOIN_SYNCING, (void*)&OnJoinSyncStart, context);
 
 	AddTransition(NCS_JOIN_SYNCING, (uint)NMT_CHAT, NCS_JOIN_SYNCING, (void*)&OnChat, context);
 	AddTransition(NCS_JOIN_SYNCING, (uint)NMT_GAME_SETUP, NCS_JOIN_SYNCING, (void*)&OnGameSetup, context);
 	AddTransition(NCS_JOIN_SYNCING, (uint)NMT_PLAYER_ASSIGNMENT, NCS_JOIN_SYNCING, (void*)&OnPlayerAssignment, context);
+	AddTransition(NCS_JOIN_SYNCING, (uint)NMT_CLIENT_TIMEOUT, NCS_JOIN_SYNCING, (void*)&OnClientTimeout, context);
+	AddTransition(NCS_JOIN_SYNCING, (uint)NMT_CLIENT_PERFORMANCE, NCS_JOIN_SYNCING, (void*)&OnClientPerformance, context);
 	AddTransition(NCS_JOIN_SYNCING, (uint)NMT_GAME_START, NCS_JOIN_SYNCING, (void*)&OnGameStart, context);
 	AddTransition(NCS_JOIN_SYNCING, (uint)NMT_SIMULATION_COMMAND, NCS_JOIN_SYNCING, (void*)&OnInGame, context);
 	AddTransition(NCS_JOIN_SYNCING, (uint)NMT_END_COMMAND_BATCH, NCS_JOIN_SYNCING, (void*)&OnJoinSyncEndCommandBatch, context);
@@ -108,10 +113,14 @@ CNetClient::CNetClient(CGame* game) :
 	AddTransition(NCS_LOADING, (uint)NMT_CHAT, NCS_LOADING, (void*)&OnChat, context);
 	AddTransition(NCS_LOADING, (uint)NMT_GAME_SETUP, NCS_LOADING, (void*)&OnGameSetup, context);
 	AddTransition(NCS_LOADING, (uint)NMT_PLAYER_ASSIGNMENT, NCS_LOADING, (void*)&OnPlayerAssignment, context);
+	AddTransition(NCS_LOADING, (uint)NMT_CLIENT_TIMEOUT, NCS_LOADING, (void*)&OnClientTimeout, context);
+	AddTransition(NCS_LOADING, (uint)NMT_CLIENT_PERFORMANCE, NCS_LOADING, (void*)&OnClientPerformance, context);
 	AddTransition(NCS_LOADING, (uint)NMT_LOADED_GAME, NCS_INGAME, (void*)&OnLoadedGame, context);
 
 	AddTransition(NCS_INGAME, (uint)NMT_REJOINED, NCS_INGAME, (void*)&OnRejoined, context);
 	AddTransition(NCS_INGAME, (uint)NMT_KICKED, NCS_INGAME, (void*)&OnKicked, context);
+	AddTransition(NCS_INGAME, (uint)NMT_CLIENT_TIMEOUT, NCS_INGAME, (void*)&OnClientTimeout, context);
+	AddTransition(NCS_INGAME, (uint)NMT_CLIENT_PERFORMANCE, NCS_INGAME, (void*)&OnClientPerformance, context);
 	AddTransition(NCS_INGAME, (uint)NMT_CHAT, NCS_INGAME, (void*)&OnChat, context);
 	AddTransition(NCS_INGAME, (uint)NMT_GAME_SETUP, NCS_INGAME, (void*)&OnGameSetup, context);
 	AddTransition(NCS_INGAME, (uint)NMT_PLAYER_ASSIGNMENT, NCS_INGAME, (void*)&OnPlayerAssignment, context);
@@ -170,8 +179,45 @@ void CNetClient::DestroyConnection()
 
 void CNetClient::Poll()
 {
-	if (m_Session)
-		m_Session->Poll();
+	if (!m_Session)
+		return;
+
+	CheckServerConnection();
+	m_Session->Poll();
+}
+
+void CNetClient::CheckServerConnection()
+{
+	// Trigger local warnings if the connection to the server is bad.
+	// At most once per second.
+	std::time_t now = std::time(nullptr);
+	if (now <= m_LastConnectionCheck)
+		return;
+
+	m_LastConnectionCheck = now;
+
+	JSContext* cx = GetScriptInterface().GetContext();
+
+	// Report if we are losing the connection to the server
+	u32 lastReceived = m_Session->GetLastReceivedTime();
+	if (lastReceived > NETWORK_WARNING_TIMEOUT)
+	{
+		JS::RootedValue msg(cx);
+		GetScriptInterface().Eval("({ 'type':'netwarn', 'warntype': 'server-timeout' })", &msg);
+		GetScriptInterface().SetProperty(msg, "lastReceivedTime", lastReceived);
+		PushGuiMessage(msg);
+		return;
+	}
+
+	// Report if we have a bad ping to the server
+	u32 meanRTT = m_Session->GetMeanRTT();
+	if (meanRTT > DEFAULT_TURN_LENGTH_MP)
+	{
+		JS::RootedValue msg(cx);
+		GetScriptInterface().Eval("({ 'type':'netwarn', 'warntype': 'server-latency' })", &msg);
+		GetScriptInterface().SetProperty(msg, "meanRTT", meanRTT);
+		PushGuiMessage(msg);
+	}
 }
 
 void CNetClient::Flush()
@@ -627,6 +673,60 @@ bool CNetClient::OnKicked(void *context, CFsmEvent* event)
 	return true;
 }
 
+bool CNetClient::OnClientTimeout(void *context, CFsmEvent* event)
+{
+	// Report the timeout of some other client
+
+	ENSURE(event->GetType() == (uint)NMT_CLIENT_TIMEOUT);
+
+	CNetClient* client = (CNetClient*)context;
+	JSContext* cx = client->GetScriptInterface().GetContext();
+
+	if (client->GetCurrState() == NCS_LOADING)
+		return true;
+
+	CClientTimeoutMessage* message = (CClientTimeoutMessage*)event->GetParamRef();
+	JS::RootedValue msg(cx);
+
+	client->GetScriptInterface().Eval("({ 'type':'netwarn', 'warntype': 'client-timeout' })", &msg);
+	client->GetScriptInterface().SetProperty(msg, "guid", std::string(message->m_GUID));
+	client->GetScriptInterface().SetProperty(msg, "lastReceivedTime", message->m_LastReceivedTime);
+	client->PushGuiMessage(msg);
+
+	return true;
+}
+
+bool CNetClient::OnClientPerformance(void *context, CFsmEvent* event)
+{
+	// Performance statistics for one or multiple clients
+
+	ENSURE(event->GetType() == (uint)NMT_CLIENT_PERFORMANCE);
+
+	CNetClient* client = (CNetClient*)context;
+	JSContext* cx = client->GetScriptInterface().GetContext();
+
+	if (client->GetCurrState() == NCS_LOADING)
+		return true;
+
+	CClientPerformanceMessage* message = (CClientPerformanceMessage*)event->GetParamRef();
+	std::vector<CClientPerformanceMessage::S_m_Clients> &clients = message->m_Clients;
+
+	// Display warnings for other clients with bad ping
+	for (size_t i = 0; i < clients.size(); ++i)
+	{
+		if (clients[i].m_MeanRTT < DEFAULT_TURN_LENGTH_MP || clients[i].m_GUID == client->m_GUID)
+			continue;
+
+		JS::RootedValue msg(cx);
+		client->GetScriptInterface().Eval("({ 'type':'netwarn', 'warntype': 'client-latency' })", &msg);
+		client->GetScriptInterface().SetProperty(msg, "guid", clients[i].m_GUID);
+		client->GetScriptInterface().SetProperty(msg, "meanRTT", clients[i].m_MeanRTT);
+		client->PushGuiMessage(msg);
+	}
+
+	return true;
+}
+
 bool CNetClient::OnLoadedGame(void* context, CFsmEvent* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_LOADED_GAME);
diff --git a/source/network/NetClient.h b/source/network/NetClient.h
index 98d153176a..b07edb4afb 100644
--- a/source/network/NetClient.h
+++ b/source/network/NetClient.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2015 Wildfire Games.
+/* Copyright (C) 2016 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -108,6 +108,11 @@ public:
 	 */
 	void Poll();
 
+	/**
+	 * Locally triggers a GUI message if the connection to the server is being lost or has bad latency.
+	 */
+	void CheckServerConnection();
+
 	/**
 	 * Flush any queued outgoing network messages.
 	 * This should be called soon after sending a group of messages that may be batched together.
@@ -202,6 +207,8 @@ private:
 	static bool OnJoinSyncEndCommandBatch(void* context, CFsmEvent* event);
 	static bool OnRejoined(void* context, CFsmEvent* event);
 	static bool OnKicked(void* context, CFsmEvent* event);
+	static bool OnClientTimeout(void* context, CFsmEvent* event);
+	static bool OnClientPerformance(void* context, CFsmEvent* event);
 	static bool OnLoadedGame(void* context, CFsmEvent* event);
 
 	/**
@@ -240,6 +247,9 @@ private:
 
 	/// Serialized game state received when joining an in-progress game
 	std::string m_JoinSyncBuffer;
+
+	/// Time when the server was last checked for timeouts and bad latency
+	std::time_t m_LastConnectionCheck;
 };
 
 /// Global network client for the standard game
diff --git a/source/network/NetMessage.cpp b/source/network/NetMessage.cpp
index bf35f2639d..b37263dd52 100644
--- a/source/network/NetMessage.cpp
+++ b/source/network/NetMessage.cpp
@@ -1,4 +1,4 @@
-/* Copyright (C) 2015 Wildfire Games.
+/* Copyright (C) 2016 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -139,6 +139,14 @@ CNetMessage* CNetMessageFactory::CreateMessage(const void* pData,
 		pNewMessage = new CKickedMessage;
 		break;
 
+	case NMT_CLIENT_TIMEOUT:
+		pNewMessage = new CClientTimeoutMessage;
+		break;
+
+	case NMT_CLIENT_PERFORMANCE:
+		pNewMessage = new CClientPerformanceMessage;
+		break;
+
 	case NMT_LOADED_GAME:
 		pNewMessage = new CLoadedGameMessage;
 		break;
diff --git a/source/network/NetMessages.h b/source/network/NetMessages.h
index 0ee8097217..b27f307d26 100644
--- a/source/network/NetMessages.h
+++ b/source/network/NetMessages.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2015 Wildfire Games.
+/* Copyright (C) 2016 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -28,7 +28,7 @@
 
 #define PS_PROTOCOL_MAGIC				0x5073013f		// 'P', 's', 0x01, '?'
 #define PS_PROTOCOL_MAGIC_RESPONSE		0x50630121		// 'P', 'c', 0x01, '!'
-#define PS_PROTOCOL_VERSION				0x01010008		// Arbitrary protocol
+#define PS_PROTOCOL_VERSION				0x01010009		// Arbitrary protocol
 #define PS_DEFAULT_PORT					0x5073			// 'P', 's'
 
 // Defines the list of message types. The order of the list must not change.
@@ -60,6 +60,9 @@ enum NetMessageType
 	NMT_REJOINED,
 	NMT_KICKED,
 
+	NMT_CLIENT_TIMEOUT,
+	NMT_CLIENT_PERFORMANCE,
+
 	NMT_LOADED_GAME,
 	NMT_GAME_START,
 	NMT_END_COMMAND_BATCH,
@@ -167,6 +170,18 @@ START_NMT_CLASS_(Kicked, NMT_KICKED)
 	NMT_FIELD_INT(m_Ban, u8, 1)
 END_NMT_CLASS()
 
+START_NMT_CLASS_(ClientTimeout, NMT_CLIENT_TIMEOUT)
+	NMT_FIELD(CStr8, m_GUID)
+	NMT_FIELD_INT(m_LastReceivedTime, u32, 4)
+END_NMT_CLASS()
+
+START_NMT_CLASS_(ClientPerformance, NMT_CLIENT_PERFORMANCE)
+	NMT_START_ARRAY(m_Clients)
+		NMT_FIELD(CStr8, m_GUID)
+		NMT_FIELD_INT(m_MeanRTT, u32, 4)
+	NMT_END_ARRAY()
+END_NMT_CLASS()
+
 START_NMT_CLASS_(LoadedGame, NMT_LOADED_GAME)
 	NMT_FIELD_INT(m_CurrentTurn, u32, 4)
 END_NMT_CLASS()
diff --git a/source/network/NetServer.cpp b/source/network/NetServer.cpp
index e0bcfeb40a..debff06e29 100644
--- a/source/network/NetServer.cpp
+++ b/source/network/NetServer.cpp
@@ -121,7 +121,8 @@ CNetServerWorker::CNetServerWorker(int autostartPlayers) :
 	m_AutostartPlayers(autostartPlayers),
 	m_Shutdown(false),
 	m_ScriptInterface(NULL),
-	m_NextHostID(1), m_Host(NULL), m_HostGUID(), m_Stats(NULL)
+	m_NextHostID(1), m_Host(NULL), m_HostGUID(), m_Stats(NULL),
+	m_LastConnectionCheck(0)
 {
 	m_State = SERVER_STATE_UNCONNECTED;
 
@@ -451,6 +452,8 @@ bool CNetServerWorker::RunStep()
 	for (size_t i = 0; i < m_Sessions.size(); ++i)
 		m_Sessions[i]->GetFileTransferer().Poll();
 
+	CheckClientConnections();
+
 	// Process network events:
 
 	ENetEvent event;
@@ -549,6 +552,55 @@ bool CNetServerWorker::RunStep()
 	return true;
 }
 
+void CNetServerWorker::CheckClientConnections()
+{
+	if (m_State == SERVER_STATE_LOADING)
+		return;
+
+	// Send messages at most once per second
+	std::time_t now = std::time(nullptr);
+	if (now <= m_LastConnectionCheck)
+		return;
+
+	m_LastConnectionCheck = now;
+
+	for (size_t i = 0; i < m_Sessions.size(); ++i)
+	{
+		u32 lastReceived = m_Sessions[i]->GetLastReceivedTime();
+		u32 meanRTT = m_Sessions[i]->GetMeanRTT();
+
+		CNetMessage* message = nullptr;
+
+		// Report if we didn't hear from the client since few seconds
+		if (lastReceived > NETWORK_WARNING_TIMEOUT)
+		{
+			CClientTimeoutMessage* msg = new CClientTimeoutMessage();
+			msg->m_GUID = m_Sessions[i]->GetGUID();
+			msg->m_LastReceivedTime = lastReceived;
+			message = msg;
+		}
+		// Report if the client has bad ping
+		else if (meanRTT > DEFAULT_TURN_LENGTH_MP)
+		{
+			CClientPerformanceMessage* msg = new CClientPerformanceMessage();
+			CClientPerformanceMessage::S_m_Clients client;
+			client.m_GUID = m_Sessions[i]->GetGUID();
+			client.m_MeanRTT = meanRTT;
+			msg->m_Clients.push_back(client);
+			message = msg;
+		}
+
+		// Send to all clients except the affected one
+		// (since that will show the locally triggered warning instead)
+		if (message)
+			for (size_t j = 0; j < m_Sessions.size(); ++j)
+				if (i != j)
+					m_Sessions[j]->SendMessage(message);
+
+		SAFE_DELETE(message);
+	}
+}
+
 void CNetServerWorker::HandleMessageReceive(const CNetMessage* message, CNetServerSession* session)
 {
 	// Handle non-FSM messages first
diff --git a/source/network/NetServer.h b/source/network/NetServer.h
index 5794c15756..0d3cc8e505 100644
--- a/source/network/NetServer.h
+++ b/source/network/NetServer.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2015 Wildfire Games.
+/* Copyright (C) 2016 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -281,6 +281,10 @@ private:
 
 	void HandleMessageReceive(const CNetMessage* message, CNetServerSession* session);
 
+	/**
+	 * Send a network warning if the connection to a client is being lost or has bad latency.
+	 */
+	void CheckClientConnections();
 
 	/**
 	 * Internal script context for (de)serializing script messages,
@@ -331,6 +335,11 @@ private:
 	 */
 	std::string m_JoinSyncFile;
 
+	/**
+	 *  Time when the clients connections were last checked for timeouts and latency.
+	 */
+	std::time_t m_LastConnectionCheck;
+
 private:
 	// Thread-related stuff:
 
diff --git a/source/network/NetSession.cpp b/source/network/NetSession.cpp
index 3e97124927..e9a1925b29 100644
--- a/source/network/NetSession.cpp
+++ b/source/network/NetSession.cpp
@@ -25,6 +25,8 @@
 #include "ps/CLogger.h"
 #include "scriptinterface/ScriptInterface.h"
 
+const u32 NETWORK_WARNING_TIMEOUT = 4000;
+
 static const int CHANNEL_COUNT = 1;
 
 CNetClientSession::CNetClientSession(CNetClient& client) :
@@ -168,6 +170,22 @@ bool CNetClientSession::SendMessage(const CNetMessage* message)
 	return CNetHost::SendMessage(message, m_Server, "server");
 }
 
+u32 CNetClientSession::GetLastReceivedTime() const
+{
+	if (!m_Server)
+		return 0;
+
+	return enet_time_get() - m_Server->lastReceiveTime;
+}
+
+u32 CNetClientSession::GetMeanRTT() const
+{
+	if (!m_Server)
+		return 0;
+
+	return m_Server->roundTripTime;
+}
+
 
 
 CNetServerSession::CNetServerSession(CNetServerWorker& server, ENetPeer* peer) :
@@ -184,6 +202,22 @@ CStr CNetServerSession::GetIPAddress() const
 	return ipAddress;
 }
 
+u32 CNetServerSession::GetLastReceivedTime() const
+{
+	if (!m_Peer)
+		return 0;
+
+	return enet_time_get() - m_Peer->lastReceiveTime;
+}
+
+u32 CNetServerSession::GetMeanRTT() const
+{
+	if (!m_Peer)
+		return 0;
+
+	return m_Peer->roundTripTime;
+}
+
 void CNetServerSession::Disconnect(u32 reason)
 {
 	Update((uint)NMT_CONNECTION_LOST, NULL);
diff --git a/source/network/NetSession.h b/source/network/NetSession.h
index 40362dfb97..a86db64804 100644
--- a/source/network/NetSession.h
+++ b/source/network/NetSession.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2015 Wildfire Games.
+/* Copyright (C) 2016 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -24,6 +24,11 @@
 #include "ps/CStr.h"
 #include "scriptinterface/ScriptVal.h"
 
+/**
+ * Report the peer if we didn't receive a packet after this time (milliseconds).
+ */
+extern const u32 NETWORK_WARNING_TIMEOUT;
+
 class CNetClient;
 class CNetServerWorker;
 
@@ -83,6 +88,16 @@ public:
 	 */
 	virtual bool SendMessage(const CNetMessage* message);
 
+	/**
+	 * Number of milliseconds since the most recent packet of the server was received.
+	 */
+	u32 GetLastReceivedTime() const;
+
+	/**
+	 * Average round trip time to the server.
+	 */
+	u32 GetMeanRTT() const;
+
 	CNetFileTransferer& GetFileTransferer() { return m_FileTransferer; }
 
 private:
@@ -124,6 +139,16 @@ public:
 
 	CStr GetIPAddress() const;
 
+	/**
+	 * Number of milliseconds since the latest packet of that client was received.
+	 */
+	u32 GetLastReceivedTime() const;
+
+	/**
+	 * Average round trip time to the client.
+	 */
+	u32 GetMeanRTT() const;
+
 	/**
 	 * Sends a disconnection notification to the client,
 	 * and sends a NMT_CONNECTION_LOST message to the session FSM.
diff --git a/source/network/NetTurnManager.cpp b/source/network/NetTurnManager.cpp
index 350d6ddf05..52f8938a93 100644
--- a/source/network/NetTurnManager.cpp
+++ b/source/network/NetTurnManager.cpp
@@ -38,8 +38,8 @@
 #include <fstream>
 #include <iomanip>
 
-static const int DEFAULT_TURN_LENGTH_MP = 500;
-static const int DEFAULT_TURN_LENGTH_SP = 200;
+const u32 DEFAULT_TURN_LENGTH_MP = 500;
+const u32 DEFAULT_TURN_LENGTH_SP = 200;
 
 static const int COMMAND_DELAY = 2;
 
diff --git a/source/network/NetTurnManager.h b/source/network/NetTurnManager.h
index 8c3aa4f21a..d426b436a3 100644
--- a/source/network/NetTurnManager.h
+++ b/source/network/NetTurnManager.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2015 Wildfire Games.
+/* Copyright (C) 2016 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -26,6 +26,9 @@
 #include <map>
 #include <vector>
 
+extern const u32 DEFAULT_TURN_LENGTH_MP;
+extern const u32 DEFAULT_TURN_LENGTH_SP;
+
 class CNetServerWorker;
 class CNetClient;
 class CSimulationMessage;