(svn r7505) -Feature: show NewGRFs used on a game server, show which NewGRFs you do and do not have.

-Feature: show NewGRF compatability of network games in the Game List window; a green square if you got the same OpenTTD version and have the needed NewGRF, a red square if the version does not match and a yellow square if the version matches, but the client is missing at least one of the NewGRFs.

9 files changed, 333 insertions, 23 deletions

diff --git a/lang/english.txt b/lang/english.txt
index 11512303e..26360d36f 100644
--- a/lang/english.txt
+++ b/lang/english.txt
@@ -1308,6 +1308,7 @@ STR_NETWORK_PASSWORD                                            :{SILVER}Passwor
 STR_NETWORK_SERVER_OFFLINE                                      :{SILVER}SERVER OFFLINE
 STR_NETWORK_SERVER_FULL                                         :{SILVER}SERVER FULL
 STR_NETWORK_VERSION_MISMATCH                                    :{SILVER}VERSION MISMATCH
+STR_NETWORK_GRF_MISMATCH                                        :{SILVER}NEWGRF MISMATCH
 
 STR_NETWORK_JOIN_GAME                                           :{BLACK}Join game
 
diff --git a/network.h b/network.h
index 1b3416a51..5453658e4 100644
--- a/network.h
+++ b/network.h
@@ -54,6 +54,17 @@ enum {
 	NETWORK_CLIENT_NAME_LENGTH =  25,
 	NETWORK_RCONCOMMAND_LENGTH = 500,
 
+	NETWORK_GRF_NAME_LENGTH    =  80, ///< Maximum length of the name of a GRF
+	/* Maximum number of GRFs that can be sent.
+	 * This value is related to number of handles (files) OpenTTD can open.
+	 * This is currently 64 and about 10 are currently used when OpenTTD loads
+	 * without any NewGRFs. Therefore one can only load about 55 NewGRFs, so
+	 * this is not a limit, but rather a way to easily check whether the limit
+	 * imposed by the handle count is reached. Secondly it isn't possible to
+	 * send much more GRF IDs + MD5sums in the PACKET_UDP_SERVER_RESPONSE, due
+	 * to the limited size of UDP packets. */
+	NETWORK_MAX_GRF_COUNT      =  55,
+
 	NETWORK_NUM_LANGUAGES      =   4,
 };
 
@@ -66,7 +77,8 @@ typedef struct NetworkGameInfo {
 	char server_revision[NETWORK_REVISION_LENGTH];  // The SVN version number the server is using (e.g.: 'r304')
 	                                                //  It even shows a SVN version in release-version, so
 	                                                //  it is easy to compare if a server is of the correct version
-	bool compatible;                                // Can we connect to this server or not? (based on server_revision)
+	bool version_compatible;                        // Can we connect to this server or not? (based on server_revision)
+	bool compatible;                                // Can we connect to this server or not? (based on server_revision _and_ grf_match
 	byte server_lang;                               // Language of the server (we should make a nice table for this)
 	byte use_password;                              // Is set to != 0 if it uses a password
 	char server_password[NETWORK_PASSWORD_LENGTH];  // On the server: the game password, on the client: != "" if server has password
@@ -84,6 +96,7 @@ typedef struct NetworkGameInfo {
 	byte map_set;                                   // Graphical set
 	bool dedicated;                                 // Is this a dedicated server?
 	char rcon_password[NETWORK_PASSWORD_LENGTH];    // RCon password for the server. "" if rcon is disabled
+	struct GRFConfig *grfconfig;                    // List of NewGRF files required
 } NetworkGameInfo;
 
 typedef struct NetworkPlayerInfo {
diff --git a/network_data.h b/network_data.h
index 80724a8de..16263c776 100644
--- a/network_data.h
+++ b/network_data.h
@@ -18,7 +18,7 @@
 #define NETWORK_EMPTY_INDEX 0
 
 // What version of game-info do we use?
-#define NETWORK_GAME_INFO_VERSION 3
+#define NETWORK_GAME_INFO_VERSION 4
 // What version of company info is this?
 #define NETWORK_COMPANY_INFO_VERSION 4
 // What version of master-server-protocol do we use?
diff --git a/network_gamelist.c b/network_gamelist.c
index 57f24b281..f52272307 100644
--- a/network_gamelist.c
+++ b/network_gamelist.c
@@ -5,6 +5,7 @@
 #include "stdafx.h"
 #include "debug.h"
 #include "network_data.h"
+#include "newgrf_config.h"
 
 // This file handles the GameList
 // Also, it handles the request to a server for data about the server
@@ -57,6 +58,9 @@ void NetworkGameListRemoveItem(NetworkGameList *remove)
 				prev_item->next = remove->next;
 			}
 
+			/* Remove GRFConfig information */
+			ClearGRFConfigList(remove->info.grfconfig);
+
 			free(remove);
 			DEBUG(net, 4) ("[NET][GameList] Removed server from list");
 			UpdateNetworkGameWindow(false);
diff --git a/network_gui.c b/network_gui.c
index 30efc8e51..4f5591222 100644
--- a/network_gui.c
+++ b/network_gui.c
@@ -26,6 +26,7 @@
 #include "settings.h"
 #include "string.h"
 #include "town.h"
+#include "newgrf.h"
 
 #define BGC 5
 #define BTC 15
@@ -241,6 +242,10 @@ static void NetworkGameWindowWndProc(Window *w, WindowEvent *e)
 				sel->info.clients_on >= sel->info.clients_max || // Server full
 				!sel->info.compatible); // Revision mismatch
 
+		SetWindowWidgetHiddenState(w, 18, sel == NULL ||
+				!sel->online ||
+				sel->info.grfconfig == NULL);
+
 		SetDParam(0, 0x00);
 		SetDParam(7, _lan_internet_types_dropdown[_network_lan_internet]);
 		DrawWindowWidgets(w);
@@ -288,7 +293,7 @@ static void NetworkGameWindowWndProc(Window *w, WindowEvent *e)
 					if (cur_item->info.use_password) DrawSprite(SPR_LOCK, w->widget[8].left + 5, y - 1);
 
 					// draw red or green icon, depending on compatibility with server.
-					DrawSprite(SPR_BLOT | (cur_item->info.compatible ? PALETTE_TO_GREEN : PALETTE_TO_RED), w->widget[8].left + 15, y);
+					DrawSprite(SPR_BLOT | (cur_item->info.compatible ? PALETTE_TO_GREEN : (cur_item->info.version_compatible ? PALETTE_TO_YELLOW : PALETTE_TO_RED)), w->widget[8].left + 15, y);
 
 					// draw flag according to server language
 					DrawSprite(SPR_FLAGS_BASE + cur_item->info.server_lang, w->widget[8].left + 25, y);
@@ -362,7 +367,7 @@ static void NetworkGameWindowWndProc(Window *w, WindowEvent *e)
 			y += 2;
 
 			if (!sel->info.compatible) {
-				DrawStringCentered(425, y, STR_NETWORK_VERSION_MISMATCH, 0); // server mismatch
+				DrawStringCentered(425, y, sel->info.version_compatible ? STR_NETWORK_GRF_MISMATCH : STR_NETWORK_VERSION_MISMATCH, 0); // server mismatch
 			} else if (sel->info.clients_on == sel->info.clients_max) {
 				// Show: server full, when clients_on == clients_max
 				DrawStringCentered(425, y, STR_NETWORK_SERVER_FULL, 0); // server full
@@ -436,6 +441,9 @@ static void NetworkGameWindowWndProc(Window *w, WindowEvent *e)
 			if (nd->server != NULL)
 				NetworkQueryServer(nd->server->info.hostname, nd->server->port, true);
 			break;
+		case 18: // NewGRF Settings
+			if (nd->server != NULL) ShowNewGRFSettings(false, false, &nd->server->info.grfconfig);
+			break;
 
 	}	break;
 
@@ -496,7 +504,7 @@ static void NetworkGameWindowWndProc(Window *w, WindowEvent *e)
 static const Widget _network_game_window_widgets[] = {
 {   WWT_CLOSEBOX,   RESIZE_NONE,   BGC,     0,    10,     0,    13, STR_00C5,                    STR_018B_CLOSE_WINDOW},
 {    WWT_CAPTION,   RESIZE_NONE,   BGC,    11,   549,     0,    13, STR_NETWORK_MULTIPLAYER,     STR_NULL},
-{      WWT_PANEL,   RESIZE_NONE,   BGC,     0,   549,    14,   249, 0x0,                         STR_NULL},
+{      WWT_PANEL,   RESIZE_NONE,   BGC,     0,   549,    14,   261, 0x0,                         STR_NULL},
 
 /* LEFT SIDE */
 {      WWT_PANEL,   RESIZE_NONE,   BGC,   310,   461,    22,    33, 0x0,                         STR_NETWORK_ENTER_NAME_TIP},
@@ -508,26 +516,28 @@ static const Widget _network_game_window_widgets[] = {
 { WWT_PUSHTXTBTN,   RESIZE_NONE,   BTC,   171,   250,    42,    53, STR_NETWORK_CLIENTS_CAPTION, STR_NETWORK_CLIENTS_CAPTION_TIP},
 { WWT_PUSHTXTBTN,   RESIZE_NONE,   BTC,   251,   290,    42,    53, STR_EMPTY,                   STR_NETWORK_INFO_ICONS_TIP},
 
-{     WWT_MATRIX,   RESIZE_NONE,   BGC,    10,   290,    54,   222, (12 << 8) + 1,               STR_NETWORK_CLICK_GAME_TO_SELECT},
-{  WWT_SCROLLBAR,   RESIZE_NONE,   BGC,   291,   302,    42,   222, STR_NULL,                    STR_0190_SCROLL_BAR_SCROLLS_LIST},
+{     WWT_MATRIX,   RESIZE_NONE,   BGC,    10,   290,    54,   234, (12 << 8) + 1,               STR_NETWORK_CLICK_GAME_TO_SELECT},
+{  WWT_SCROLLBAR,   RESIZE_NONE,   BGC,   291,   302,    42,   234, STR_NULL,                    STR_0190_SCROLL_BAR_SCROLLS_LIST},
 
-{ WWT_PUSHTXTBTN,   RESIZE_NONE,   BTC,    30,   130,   232,   243, STR_NETWORK_FIND_SERVER,     STR_NETWORK_FIND_SERVER_TIP},
-{ WWT_PUSHTXTBTN,   RESIZE_NONE,   BTC,   180,   280,   232,   243, STR_NETWORK_ADD_SERVER,      STR_NETWORK_ADD_SERVER_TIP},
+{ WWT_PUSHTXTBTN,   RESIZE_NONE,   BTC,    30,   130,   244,   255, STR_NETWORK_FIND_SERVER,     STR_NETWORK_FIND_SERVER_TIP},
+{ WWT_PUSHTXTBTN,   RESIZE_NONE,   BTC,   180,   280,   244,   255, STR_NETWORK_ADD_SERVER,      STR_NETWORK_ADD_SERVER_TIP},
 
 /* RIGHT SIDE */
-{ WWT_PUSHTXTBTN,   RESIZE_NONE,   BTC,   315,   415,   232,   243, STR_NETWORK_START_SERVER,    STR_NETWORK_START_SERVER_TIP},
-{ WWT_PUSHTXTBTN,   RESIZE_NONE,   BTC,   430,   535,   232,   243, STR_012E_CANCEL,             STR_NULL},
+{ WWT_PUSHTXTBTN,   RESIZE_NONE,   BTC,   315,   415,   244,   255, STR_NETWORK_START_SERVER,    STR_NETWORK_START_SERVER_TIP},
+{ WWT_PUSHTXTBTN,   RESIZE_NONE,   BTC,   430,   535,   244,   255, STR_012E_CANCEL,             STR_NULL},
+
+{      WWT_PANEL,   RESIZE_NONE,   BGC,   310,   540,    42,   234, 0x0,                         STR_NULL},
 
-{      WWT_PANEL,   RESIZE_NONE,   BGC,   310,   540,    42,   222, 0x0,                         STR_NULL},
+{ WWT_PUSHTXTBTN,   RESIZE_NONE,   BTC,   315,   415,   213,   224, STR_NETWORK_JOIN_GAME,       STR_NULL},
+{ WWT_PUSHTXTBTN,   RESIZE_NONE,   BTC,   430,   535,   213,   224, STR_NETWORK_REFRESH,         STR_NETWORK_REFRESH_TIP},
 
-{ WWT_PUSHTXTBTN,   RESIZE_NONE,   BTC,   315,   415,   201,   212, STR_NETWORK_JOIN_GAME,       STR_NULL},
-{ WWT_PUSHTXTBTN,   RESIZE_NONE,   BTC,   430,   535,   201,   212, STR_NETWORK_REFRESH,         STR_NETWORK_REFRESH_TIP},
+{ WWT_PUSHTXTBTN,   RESIZE_NONE,   BTC,   430,   535,   195,   206, STR_NEWGRF_SETTINGS_BUTTON,  STR_NULL},
 
 {   WIDGETS_END},
 };
 
 static const WindowDesc _network_game_window_desc = {
-	WDP_CENTER, WDP_CENTER, 550, 250,
+	WDP_CENTER, WDP_CENTER, 550, 262,
 	WC_NETWORK_WINDOW,0,
 	WDF_STD_TOOLTIPS | WDF_DEF_WIDGET | WDF_UNCLICK_BUTTONS,
 	_network_game_window_widgets,
diff --git a/network_udp.c b/network_udp.c
index ca66dfd01..680c984fc 100644
--- a/network_udp.c
+++ b/network_udp.c
@@ -11,6 +11,7 @@
 #include "network_gamelist.h"
 #include "network_udp.h"
 #include "variables.h"
+#include "newgrf_config.h"
 
 //
 // This file handles all the LAN-stuff
@@ -28,6 +29,8 @@ typedef enum {
 	PACKET_UDP_CLIENT_GET_LIST,      // Request for serverlist from master server
 	PACKET_UDP_MASTER_RESPONSE_LIST, // Response from master server with server ip's + port's
 	PACKET_UDP_SERVER_UNREGISTER,    // Request to be removed from the server-list
+	PACKET_UDP_CLIENT_GET_NEWGRFS,   // Requests the name for a list of GRFs (GRF_ID and MD5)
+	PACKET_UDP_SERVER_NEWGRFS,       // Sends the list of NewGRF's requested.
 	PACKET_UDP_END
 } PacketUDPType;
 
@@ -42,6 +45,34 @@ static void NetworkSendUDP_Packet(SOCKET udp, Packet* p, struct sockaddr_in* rec
 
 static NetworkClientState _udp_cs;
 
+/**
+ * Serializes the GRFIdentifier (GRF ID and MD5 checksum) to the packet
+ * @param p the packet to write the data to
+ * @param c the configuration to write the GRF ID and MD5 checksum from
+ */
+static void NetworkSend_GRFIdentifier(Packet *p, const GRFConfig *c)
+{
+	uint j;
+	NetworkSend_uint32(p, c->grfid);
+	for (j = 0; j < sizeof(c->md5sum); j++) {
+		NetworkSend_uint8 (p, c->md5sum[j]);
+	}
+}
+
+/**
+ * Deserializes the GRFIdentifier (GRF ID and MD5 checksum) from the packet
+ * @param p the packet to read the data from
+ * @param c the configuration to write the GRF ID and MD5 checksum to
+ */
+static void NetworkRecv_GRFIdentifier(Packet *p, GRFConfig *c)
+{
+	uint j;
+	c->grfid = NetworkRecv_uint32(&_udp_cs, p);
+	for (j = 0; j < sizeof(c->md5sum); j++) {
+		c->md5sum[j] = NetworkRecv_uint8(&_udp_cs, p);
+	}
+}
+
 DEF_UDP_RECEIVE_COMMAND(PACKET_UDP_CLIENT_FIND_SERVER)
 {
 	Packet *packet;
@@ -59,6 +90,27 @@ DEF_UDP_RECEIVE_COMMAND(PACKET_UDP_CLIENT_FIND_SERVER)
 
 	NetworkSend_uint8 (packet, NETWORK_GAME_INFO_VERSION);
 
+	/* NETWORK_GAME_INFO_VERSION = 4 */
+	{
+		/* Only send the GRF Identification (GRF_ID and MD5 checksum) of
+		 * the GRFs that are needed, i.e. the ones that the server has
+		 * selected in the NewGRF GUI and not the ones that are used due
+		 * to the fact that they are in [newgrf-static] in openttd.cfg */
+		const GRFConfig *c;
+		uint i = 0;
+
+		/* Count number of GRFs to send information about */
+		for (c = _grfconfig; c != NULL; c = c->next) {
+			if (!HASBIT(c->flags, GCF_STATIC)) i++;
+		}
+		NetworkSend_uint8 (packet, i); // Send number of GRFs
+
+		/* Send actual GRF Identifications */
+		for (c = _grfconfig; c != NULL; c = c->next) {
+			if (!HASBIT(c->flags, GCF_STATIC)) NetworkSend_GRFIdentifier(packet, c);
+		}
+	}
+
 	/* NETWORK_GAME_INFO_VERSION = 3 */
 	NetworkSend_uint32(packet, _network_game_info.game_date);
 	NetworkSend_uint32(packet, _network_game_info.start_date);
@@ -109,9 +161,41 @@ DEF_UDP_RECEIVE_COMMAND(PACKET_UDP_SERVER_RESPONSE)
 	// Find next item
 	item = NetworkGameListAddItem(inet_addr(inet_ntoa(client_addr->sin_addr)), ntohs(client_addr->sin_port));
 
+	item->info.compatible = true;
 	/* Please observer the order. In the order in which packets are sent
 	 * they are to be received */
 	switch (game_info_version) {
+		case 4: {
+			GRFConfig *c, **dst = &item->info.grfconfig;
+			const GRFConfig *f;
+			uint i;
+			uint num_grfs = NetworkRecv_uint8(&_udp_cs, p);
+
+			for (i = 0; i < num_grfs; i++) {
+				c = calloc(1, sizeof(*c));
+				NetworkRecv_GRFIdentifier(p, c);
+
+				/* Find the matching GRF file */
+				f = FindGRFConfig(c->grfid, c->md5sum);
+				if (f == NULL) {
+					/* Don't know the GRF, so mark game incompatible and the (possibly)
+					 * already resolved name for this GRF (another server has sent the
+					 * name of the GRF already */
+					item->info.compatible = false;
+					c->name     = FindUnknownGRFName(c->grfid, c->md5sum, true);
+					SETBIT(c->flags, GCF_NOT_FOUND);
+				} else {
+					c->filename = f->filename;
+					c->name     = f->name;
+					c->info     = f->info;
+				}
+				SETBIT(c->flags, GCF_COPY);
+
+				/* Append GRFConfig to the list */
+				*dst = c;
+				dst = &c->next;
+			}
+		} /* Fallthrough */
 		case 3:
 			item->info.game_date     = NetworkRecv_uint32(&_udp_cs, p);
 			item->info.start_date    = NetworkRecv_uint32(&_udp_cs, p);
@@ -146,12 +230,50 @@ DEF_UDP_RECEIVE_COMMAND(PACKET_UDP_SERVER_RESPONSE)
 				snprintf(item->info.hostname, sizeof(item->info.hostname), "%s", inet_ntoa(client_addr->sin_addr));
 
 			/* Check if we are allowed on this server based on the revision-match */
-			item->info.compatible =
+			item->info.version_compatible =
 				strcmp(item->info.server_revision, _openttd_revision) == 0 ||
 				strcmp(item->info.server_revision, NOREV_STRING) == 0;
+			item->info.compatible &= item->info.version_compatible; // Already contains match for GRFs
 			break;
 	}
 
+	{
+		/* Checks whether there needs to be a request for names of GRFs and makes
+		 * the request if necessary. GRFs that need to be requested are the GRFs
+		 * that do not exist on the clients system and we do not have the name
+		 * resolved of, i.e. the name is still UNKNOWN_GRF_NAME_PLACEHOLDER.
+		 * The in_request array and in_request_count are used so there is no need
+		 * to do a second loop over the GRF list, which can be relatively expensive
+		 * due to the string comparisons. */
+		const GRFConfig *in_request[NETWORK_MAX_GRF_COUNT];
+		const GRFConfig *c;
+		uint in_request_count = 0;
+		struct sockaddr_in out_addr;
+
+		for (c = item->info.grfconfig; c != NULL; c = c->next) {
+			if (!HASBIT(c->flags, GCF_NOT_FOUND) || strcmp(c->name, UNKNOWN_GRF_NAME_PLACEHOLDER) != 0) continue;
+			in_request[in_request_count] = c;
+			in_request_count++;
+		}
+
+		if (in_request_count > 0) {
+			/* There are 'unknown' GRFs, now send a request for them */
+			uint i;
+			Packet *packet = NetworkSend_Init(PACKET_UDP_CLIENT_GET_NEWGRFS);
+
+			NetworkSend_uint8 (packet, in_request_count);
+			for (i = 0; i < in_request_count; i++) {
+				NetworkSend_GRFIdentifier(packet, in_request[i]);
+			}
+
+			out_addr.sin_family      = AF_INET;
+			out_addr.sin_port        = htons(item->port);
+			out_addr.sin_addr.s_addr = item->ip;
+			NetworkSendUDP_Packet(_udp_client_socket, packet, &out_addr);
+			free(packet);
+		}
+	}
+
 	item->online = true;
 
 	UpdateNetworkGameWindow(false);
@@ -300,6 +422,104 @@ DEF_UDP_RECEIVE_COMMAND(PACKET_UDP_MASTER_ACK_REGISTER)
 	}
 }
 
+/**
+ * A client has requested the names of some NewGRFs.
+ *
+ * Replying this can be tricky as we have a limit of SEND_MTU bytes
+ * in the reply packet and we can send up to 100 bytes per NewGRF
+ * (GRF ID, MD5sum and NETWORK_GRF_NAME_LENGTH bytes for the name).
+ * As SEND_MTU is _much_ less than 100 * NETWORK_MAX_GRF_COUNT, it
+ * could be that a packet overflows. To stop this we only reply
+ * with the first N NewGRFs so that if the first N + 1 NewGRFs
+ * would be sent, the packet overflows.
+ * in_reply and in_reply_count are used to keep a list of GRFs to
+ * send in the reply.
+ */
+DEF_UDP_RECEIVE_COMMAND(PACKET_UDP_CLIENT_GET_NEWGRFS)
+{
+	uint8 num_grfs;
+	uint i;
+
+	const GRFConfig *in_reply[NETWORK_MAX_GRF_COUNT];
+	Packet *packet;
+	uint8 in_reply_count = 0;
+	uint packet_len = 0;
+
+	/* Just a fail-safe.. should never happen */
+	if (_udp_cs.has_quit) return;
+
+	DEBUG(net, 6)("[NET][UDP] NewGRF data request from %s:%d", inet_ntoa(client_addr->sin_addr), ntohs(client_addr->sin_port));
+
+	num_grfs = NetworkRecv_uint8 (&_udp_cs, p);
+	if (num_grfs > NETWORK_MAX_GRF_COUNT) return;
+
+	for (i = 0; i < num_grfs; i++) {
+		GRFConfig c;
+		const GRFConfig *f;
+
+		NetworkRecv_GRFIdentifier(p, &c);
+
+		/* Find the matching GRF file */
+		f = FindGRFConfig(c.grfid, c.md5sum);
+		if (f == NULL) continue; // The GRF is unknown to this server
+
+		/* If the reply might exceed the size of the packet, only reply
+		 * the current list and do not send the other data */
+		packet_len += sizeof(c.grfid) + sizeof(c.md5sum) + min(strlen(f->name) + 1, NETWORK_GRF_NAME_LENGTH);
+		if (packet_len > SEND_MTU - 4) { // 4 is 3 byte header + grf count in reply
+			break;
+		}
+		in_reply[in_reply_count] = f;
+		in_reply_count++;
+	}
+
+	if (in_reply_count == 0) return;
+
+	packet = NetworkSend_Init(PACKET_UDP_SERVER_NEWGRFS);
+	NetworkSend_uint8 (packet, in_reply_count);
+	for (i = 0; i < in_reply_count; i++) {
+		char name[NETWORK_GRF_NAME_LENGTH];
+		ttd_strlcpy(name, in_reply[i]->name, sizeof(name));
+		NetworkSend_GRFIdentifier(packet, in_reply[i]);
+		NetworkSend_string(packet, name);
+	}
+
+	NetworkSendUDP_Packet(_udp_server_socket, packet, client_addr);
+	free(packet);
+}
+
+/** The return of the client's request of the names of some NewGRFs */
+DEF_UDP_RECEIVE_COMMAND(PACKET_UDP_SERVER_NEWGRFS)
+{
+	uint8 num_grfs;
+	uint i;
+
+	/* Just a fail-safe.. should never happen */
+	if (_udp_cs.has_quit) return;
+
+	DEBUG(net, 6)("[NET][UDP] NewGRF data reply from %s:%d", inet_ntoa(client_addr->sin_addr),ntohs(client_addr->sin_port));
+
+	num_grfs = NetworkRecv_uint8 (&_udp_cs, p);
+	if (num_grfs > NETWORK_MAX_GRF_COUNT) return;
+
+	for (i = 0; i < num_grfs; i++) {
+		char *unknown_name;
+		char name[NETWORK_GRF_NAME_LENGTH];
+		GRFConfig c;
+
+		NetworkRecv_GRFIdentifier(p, &c);
+		NetworkRecv_string(&_udp_cs, p, name, sizeof(name));
+
+		/* Finds the fake GRFConfig for the just read GRF ID and MD5sum tuple.
+		 * If it exists and not resolved yet, then name of the fake GRF is
+		 * overwritten with the name from the reply. */
+		unknown_name = FindUnknownGRFName(c.grfid, c.md5sum, false);
+		if (unknown_name != NULL && strcmp(unknown_name, UNKNOWN_GRF_NAME_PLACEHOLDER) == 0) {
+			ttd_strlcpy(unknown_name, name, NETWORK_GRF_NAME_LENGTH);
+		}
+	}
+}
+
 
 // The layout for the receive-functions by UDP
 typedef void NetworkUDPPacket(Packet *p, struct sockaddr_in *client_addr);
@@ -313,7 +533,9 @@ static NetworkUDPPacket* const _network_udp_packet[] = {
 	RECEIVE_COMMAND(PACKET_UDP_MASTER_ACK_REGISTER),
 	NULL,
 	RECEIVE_COMMAND(PACKET_UDP_MASTER_RESPONSE_LIST),
-	NULL
+	NULL,
+	RECEIVE_COMMAND(PACKET_UDP_CLIENT_GET_NEWGRFS),
+	RECEIVE_COMMAND(PACKET_UDP_SERVER_NEWGRFS),
 };
 
 
diff --git a/newgrf_config.c b/newgrf_config.c
index 7299be4fe..924c3c628 100644
--- a/newgrf_config.c
+++ b/newgrf_config.c
@@ -9,6 +9,7 @@
 #include "string.h"
 #include "saveload.h"
 #include "md5.h"
+#include "network_data.h"
 #include "newgrf.h"
 #include "newgrf_config.h"
 
@@ -83,9 +84,12 @@ bool FillGRFDetails(GRFConfig *config, bool is_static)
 
 void ClearGRFConfig(GRFConfig *config)
 {
-	free(config->filename);
-	free(config->name);
-	free(config->info);
+	/* GCF_COPY as in NOT strdupped/alloced the filename, name and info */
+	if (!HASBIT(config->flags, GCF_COPY)) {
+		free(config->filename);
+		free(config->name);
+		free(config->info);
+	}
 	free(config);
 }
 
@@ -264,6 +268,55 @@ const GRFConfig *FindGRFConfig(uint32 grfid, uint8 *md5sum)
 	return NULL;
 }
 
+/** Structure for UnknownGRFs; this is a lightweight variant of GRFConfig */
+typedef struct UnknownGRF UnknownGRF;
+struct UnknownGRF {
+	UnknownGRF *next;
+	uint32 grfid;
+	uint8  md5sum[16];
+	char   name[NETWORK_GRF_NAME_LENGTH];
+};
+
+/**
+ * Finds the name of a NewGRF in the list of names for unknown GRFs. An
+ * unknown GRF is a GRF where the .grf is not found during scanning.
+ *
+ * The names are resolved via UDP calls to servers that should know the name,
+ * though the replies may not come. This leaves "<Unknown>" as name, though
+ * that shouldn't matter _very_ much as they need GRF crawler or so to look
+ * up the GRF anyway and that works better with the GRF ID.
+ *
+ * @param grfid  the GRF ID part of the 'unique' GRF identifier
+ * @param md5sum the MD5 checksum part of the 'unique' GRF identifier
+ * @param create whether to create a new GRFConfig if the GRFConfig did not
+ *               exist in the fake list of GRFConfigs.
+ * @return the GRFConfig with the given GRF ID and MD5 checksum or NULL when
+ *         it does not exist and create is false. This value must NEVER be
+ *         freed by the caller.
+ */
+char *FindUnknownGRFName(uint32 grfid, uint8 *md5sum, bool create)
+{
+	UnknownGRF *grf;
+	static UnknownGRF *unknown_grfs = NULL;
+
+	for (grf = unknown_grfs; grf != NULL; grf = grf->next) {
+		if (grf->grfid == grfid) {
+			if (memcmp(md5sum, grf->md5sum, sizeof(grf->md5sum)) == 0) return grf->name;
+		}
+	}
+
+	if (!create) return NULL;
+
+	grf = calloc(1, sizeof(*grf));
+	grf->grfid = grfid;
+	grf->next  = unknown_grfs;
+	ttd_strlcpy(grf->name, UNKNOWN_GRF_NAME_PLACEHOLDER, sizeof(grf->name));
+	memcpy(grf->md5sum, md5sum, sizeof(grf->md5sum));
+
+	unknown_grfs = grf;
+	return grf->name;
+}
+
 
 /* Retrieve a NewGRF from the current config by its grfid */
 GRFConfig *GetGRFConfig(uint32 grfid)
diff --git a/newgrf_config.h b/newgrf_config.h
index 2cee7429b..42ab2feef 100644
--- a/newgrf_config.h
+++ b/newgrf_config.h
@@ -11,6 +11,7 @@ enum {
 	GCF_SYSTEM,
 	GCF_UNSAFE,
 	GCF_STATIC,
+	GCF_COPY,      ///< The data is copied from a grf in _all_grfs
 };
 
 typedef struct GRFConfig {
@@ -52,4 +53,8 @@ char *GRFBuildParamList(char *dst, const GRFConfig *c, const char *last);
 /* In newgrf_gui.c */
 void ShowNewGRFSettings(bool editable, bool show_params, GRFConfig **config);
 
+/* For communication about GRFs over the network */
+#define UNKNOWN_GRF_NAME_PLACEHOLDER "<Unknown>"
+char *FindUnknownGRFName(uint32 grfid, uint8 *md5sum, bool create);
+
 #endif /* NEWGRF_CONFIG_H */
diff --git a/newgrf_gui.c b/newgrf_gui.c
index b31c0b177..1b01a1a5a 100644
--- a/newgrf_gui.c
+++ b/newgrf_gui.c
@@ -43,9 +43,11 @@ static void ShowNewGRFInfo(const GRFConfig *c, uint x, uint y, uint w, bool show
 	char *s;
 	uint i;
 
-	/* Draw filename */
-	SetDParamStr(0, c->filename);
-	y += DrawStringMultiLine(x, y, STR_NEWGRF_FILENAME, w);
+	/* Draw filename or not if it is not known (GRF sent over internet) */
+	if (c->filename != NULL) {
+		SetDParamStr(0, c->filename);
+		y += DrawStringMultiLine(x, y, STR_NEWGRF_FILENAME, w);
+	}
 
 	/* Prepare and draw GRF ID */
 	snprintf(buff, lengthof(buff), "%08X", (uint32)BSWAP32(c->grfid));