Fix: [Network] Prevent an empty server name to be set anywhere

src/lang/english.txt

@@ -2204,6 +2204,7 @@ STR_NETWORK_ERROR_CLIENT_START                                  :{WHITE}Could no
 STR_NETWORK_ERROR_TIMEOUT                                       :{WHITE}Connection #{NUM} timed out
 STR_NETWORK_ERROR_SERVER_ERROR                                  :{WHITE}A protocol error was detected and the connection was closed
 STR_NETWORK_ERROR_BAD_PLAYER_NAME                               :{WHITE}Your player name has not been set. The name can be set at the top of the Multiplayer window
+STR_NETWORK_ERROR_BAD_SERVER_NAME                               :{WHITE}Your server name has not been set. The name can be set at the top of the Multiplayer window
 STR_NETWORK_ERROR_WRONG_REVISION                                :{WHITE}The revision of this client does not match the server's revision
 STR_NETWORK_ERROR_WRONG_PASSWORD                                :{WHITE}Wrong password
 STR_NETWORK_ERROR_SERVER_FULL                                   :{WHITE}The server is full

src/network/network.cpp

@@ -835,10 +835,6 @@ void NetworkClientJoinGame()
 
 static void NetworkInitGameInfo()
 {
-	if (_settings_client.network.server_name.empty()) {
-		_settings_client.network.server_name = "Unnamed Server";
-	}
-
 	FillStaticNetworkServerGameInfo();
 	/* The server is a client too */
 	_network_game_info.clients_on = _network_dedicated ? 0 : 1;
@@ -851,6 +847,25 @@ static void NetworkInitGameInfo()
 	ci->client_name = _settings_client.network.client_name;
 }
 
+/**
+ * Trim the given server name in place, i.e. remove leading and trailing spaces.
+ * After the trim check whether the server name is not empty.
+ * When the server name is empty a GUI error message is shown telling the
+ * user to set the servername and this function returns false.
+ *
+ * @param server_name The server name to validate. It will be trimmed of leading
+ *                    and trailing spaces.
+ * @return True iff the server name is valid.
+ */
+bool NetworkValidateServerName(std::string &server_name)
+{
+	StrTrimInPlace(server_name);
+	if (!server_name.empty()) return true;
+
+	ShowErrorMessage(STR_NETWORK_ERROR_BAD_SERVER_NAME, INVALID_STRING_ID, WL_ERROR);
+	return false;
+}
+
 /**
  * Check whether the client and server name are set, for a dedicated server and if not set them to some default
  * value and tell the user to change this as soon as possible.
@@ -860,12 +875,14 @@ static void NetworkInitGameInfo()
 static void CheckClientAndServerName()
 {
 	static const std::string fallback_client_name = "Unnamed Client";
+	StrTrimInPlace(_settings_client.network.client_name);
 	if (_settings_client.network.client_name.empty() || _settings_client.network.client_name.compare(fallback_client_name) == 0) {
 		DEBUG(net, 1, "No \"client_name\" has been set, using \"%s\" instead. Please set this now using the \"name <new name>\" command", fallback_client_name.c_str());
 		_settings_client.network.client_name = fallback_client_name;
 	}
 
 	static const std::string fallback_server_name = "Unnamed Server";
+	StrTrimInPlace(_settings_client.network.server_name);
 	if (_settings_client.network.server_name.empty() || _settings_client.network.server_name.compare(fallback_server_name) == 0) {
 		DEBUG(net, 1, "No \"server_name\" has been set, using \"%s\" instead. Please set this now using the \"server_name <new name>\" command", fallback_server_name.c_str());
 		_settings_client.network.server_name = fallback_server_name;

src/network/network_func.h

@@ -38,6 +38,7 @@ byte NetworkSpectatorCount();
 bool NetworkIsValidClientName(const std::string_view client_name);
 bool NetworkValidateClientName();
 bool NetworkValidateClientName(std::string &client_name);
+bool NetworkValidateServerName(std::string &server_name);
 void NetworkUpdateClientName(const std::string &client_name);
 bool NetworkCompanyHasClients(CompanyID company);
 std::string NetworkChangeCompanyPassword(CompanyID company_id, std::string password);

src/network/network_gui.cpp

@@ -1095,6 +1095,7 @@ struct NetworkStartServerWindow : public Window {
 				break;
 
 			case WID_NSS_GENERATE_GAME: // Start game
+				if (!CheckServerName()) return;
 				_is_network_server = true;
 				if (_ctrl_pressed) {
 					StartNewGameWithoutGUI(GENERATE_NEW_SEED);
@@ -1104,16 +1105,19 @@ struct NetworkStartServerWindow : public Window {
 				break;
 
 			case WID_NSS_LOAD_GAME:
+				if (!CheckServerName()) return;
 				_is_network_server = true;
 				ShowSaveLoadDialog(FT_SAVEGAME, SLO_LOAD);
 				break;
 
 			case WID_NSS_PLAY_SCENARIO:
+				if (!CheckServerName()) return;
 				_is_network_server = true;
 				ShowSaveLoadDialog(FT_SCENARIO, SLO_LOAD);
 				break;
 
 			case WID_NSS_PLAY_HEIGHTMAP:
+				if (!CheckServerName()) return;
 				_is_network_server = true;
 				ShowSaveLoadDialog(FT_HEIGHTMAP,SLO_LOAD);
 				break;
@@ -1133,11 +1137,13 @@ struct NetworkStartServerWindow : public Window {
 		this->SetDirty();
 	}
 
-	void OnEditboxChanged(int wid) override
+	bool CheckServerName()
 	{
-		if (wid == WID_NSS_GAMENAME) {
-			_settings_client.network.server_name = this->name_editbox.text.buf;
-		}
+		std::string str = this->name_editbox.text.buf;
+		if (!NetworkValidateServerName(str)) return false;
+
+		SetSettingValue(GetSettingFromName("network.server_name")->AsStringSetting(), str);
+		return true;
 	}
 
 	void OnTimeout() override
@@ -2199,16 +2205,13 @@ public:
 			case WID_CL_SERVER_NAME_EDIT: {
 				if (!_network_server) break;
 
-				SetSettingValue(GetSettingFromName("network.server_name")->AsStringSetting(), StrEmpty(str) ? "Unnamed Server" : str);
+				SetSettingValue(GetSettingFromName("network.server_name")->AsStringSetting(), str);
 				this->InvalidateData();
 				break;
 			}
 
 			case WID_CL_CLIENT_NAME_EDIT: {
-				std::string client_name(str);
-				if (!NetworkValidateClientName(client_name)) break;
-
-				SetSettingValue(GetSettingFromName("network.client_name")->AsStringSetting(), client_name);
+				SetSettingValue(GetSettingFromName("network.client_name")->AsStringSetting(), str);
 				this->InvalidateData();
 				break;
 			}

src/table/settings.ini

@@ -3959,6 +3959,7 @@ length   = NETWORK_NAME_LENGTH
 flags    = SLF_NOT_IN_SAVE | SLF_NO_NETWORK_SYNC
 guiflags = SGF_NETWORK_ONLY
 def      = nullptr
+pre_cb   = NetworkValidateServerName
 post_cb  = [](auto) { UpdateClientConfigValues(); }
 cat      = SC_BASIC