15. PLUS - Bonus 3 - A LAN lobby

*NOTE: In addition to LAN lobbys, there are also ONLINE lobbys!

In addition to online lobbys, you can now also create LAN lobbys. In this tutorial we will explain how. We'll assume you haven't read the online lobby tutorial, but if you have: Creating a LAN lobby is similiar, but there are some key differences.

This part of the tutorial will explain everything you'll need to know. Before we start, please create a new project and load the sample project (add all files from the GMnet ENGINE asset).

Testing the lobby

When you press K when starting the game you will be brought to the demo lobby room. This is a very simple demo room that can only show four servers. Once we are done, you'll be able to create an even better lobby.

To test it, fire up a demo game on another PC in the network and start a server. You'll see the server in the list after a few seconds.

The new concepts: Gamenames

(This is the same text as in the online lobby tutorial)

In htme_init there is a new variable you need to change when creating your own game (keep the default for the demo project though, otherwise you can't join demo servers via the lobby):

 *  Shortname of this game
 *  + version
 *  Example: htme_demo100
self.gamename = "htme_demo100"

This string represents your game and the version of your game. If you update your game and it's server is not compatible with older versions, change this string and you can prevent players from joining older servers in the lobby (Please note that this is only for the lobby, if your players are able to connect manually, you need to implement your own way of kicking him out of the game again after he has connected, see How can my clients get the gamename and data strings after they connected? below for more info)

You can change it at any time, for example if you have multiple gamemodes you want to mark in the lobby via htme_setGamename(name) and get it via htme_getGamename().

Data strings

(This is the same text as in the online lobby tutorial)

Asside from the gamename string, there are 7 more strings that can be used to identify your game in the lobby.

Start the demo game and create a server. You will be asked to enter the name of the server and a description. These are data strings 2 and 3. The demo lobby uses them for these purposes, but when making your own game, you can use them however you want. 4-8 are unused by the demo project.

Let's open the N-key event of htme_obj_menu (this event creates the server).

You'll find this part after the server has successfully been created:

htme_setData(2,get_string("How should this server be called (for the lobby)?","GMnet ENGINE Demo Server"));
htme_setData(3,get_string("Enter a server description (for the lobby)?","A server created for the GMnet ENGINE demo project"));

As you can see, we set the server name and description right after the server was started using htme_setData(n,string). We use 2 for server name and 3 for description. You can also on the server end retrieve these strings using htme_getData(n).

If you want to update any data string later, after the server connected to the master server, you need to use htme_commitData(). This syncs all data strings to the master server. You MUST NOT use it here, because the server hasn't connected to the master server yet!

A note for GMnet PUNCH users: The gamename is data string 1.

Setting broadcast settings.

By default the servers will broadcast their information to all PCs in the LAN each 15 seconds. You can change this in htme_init by changing the value of self.lan_interval

 * Interval the servers broadcast data to the LAN, for the LAN lobby
 * @type real
self.lan_interval = 15*room_speed;

Building the lobby

Ah, the lobby. Finally we are ready to build it.

The room of the lobby is the room htme_lanlobby. This room only contains the object htme_obj_lanlobbydemo. This object controls the lobby. Let's dive into it!

The create event = "htme_demo121"

///Recieve lobby data from the master server
htme_startLANsearch(real(get_string("On which port should we search for servers?","6510")),;

This will start searching the LAN for games with the game id on the port that is asked to the player. More information on this function can be found in the usage page of htme_startLANsearch.

The Room end event


This will stop searching for LAN servers. You should run this if your player leaves the lobby

The networking event

//htme_step doesn't do that btw!

This runs the code that actually searches for LAN servers. It waits for incoming server broadcasts.

The draw event

The draw event is split up into different sub-scripts:

'Background', 'Title and Controls', 'Online servers'

Draws some background colors and some text, not important

'Servers (Loop)'

This draws the actual server list.

Let's analyze it:

///Servers (Loop)
var l = htme_getLANServers();
for (var i = 0; i<4;i++) {

First, the list htme_getLANServers() is stored in the local variable l (because it's shorter). This ds_list contains all the servers we found. It will be filled over time with all servers in the LAN.

Then it begins a loop that loops through the first 4 servers in the list we got by the master server, everything is in this loop and then it draws a nice little number for each server.

    if (ds_exists(l,ds_type_list)) {
        if (ds_list_size(l)>i) {

Now, this is the interesting part.

Ee check if it has at least as many entrys as the server we want to list. For this example we assume i is 1. That means it checks if there is atleast one server in the list. If yes, we have an entry we can now draw.

            //Get stuff from the downloadlist
            var entry = l[| i];
            var ip = entry[? "ip"];
            var port = entry[? "port"];
            var game = entry[? "data1"];
            var servername = entry[? "data2"];
            var description = entry[? "data3"];

Now the entry (a ds_map) for our server is extracted from the list and we get the gamename, which is stored in data1, the ip, which is stored in the key "ip", the name of the server, which we stored in data2, and so on.

            draw_text(70,85+80*i,servername+" | "+ip+":"+string(port));

Now we just draw everything.


Again, just some text, not important.

The press 1-4 key events

Pressing 1-4 on the keyboard will connect to that game. Let's see how!

var l = htme_getLANServers();
if (ds_exists(l,ds_type_list)) {
    if (ds_list_size(l)>0) {
        var entry = l[| 0];
        var ip = entry[? "ip"];
        var game = entry[? "data1"];

We again open the downloadlist and check if server 1 is in it, if yes we continue.

        if (game != {
           //Not compatible game, exit
           show_message("Game server or version is incompatible!");

Remember the filtering variable we created in the create-event? We use it here to check if the server is a GMnet ENGINE demo game. If not we cancel. Although this is not needed if you filtered out other games with htme_startLANsearch like we did in the create event.

        if (htme_clientStart(ip, port)) {
            //Wait for connection success!
        } else {
            show_message("Could not start client! Check your network configuration!");
    } else {
      //Do nothing - There is no server on this slot
} else {
  //Do nothing - There is no server on this slot

This is the rest of the script. We call htme_clientStart with the ip we got from the list the port.

Afer that we just go to the waiting room. Done! The rest is the default client connection you know and love.

And this is how you create a lobby! Now go ahead and do it! :)

Anything missing?

If this bonus chapter lacks something important, please let me know. If you have any problems feel free to contact me. I know this is quite complicated compared to the rest, so don't be frustrated when you have problems.

» Next topic: BONUS 4 - Event Handlers for Connecting/Disconnecting

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