Use commands.md

Intro

This is how I manage data transfer for the multiplayer functionality of my mod The Only Cure. It's not necessarily the best way, but it works well.

I'm going to show you two things:

• From client, send a command to a player
• From client, request data from another client

Understand commands

The two main functions are:

• sendClientCommand(module, command, arg) To send a command from client to the server
• sendServerCommand(player, module, command, arg) To send a command from the server to players. Note: if player is empty, send to all player.

module is a string which is used to categorize commands. I recommend using the same everywhere for your mod, using your mod ID is a good idea. I use "TOC" for my mod.
command is a string too. This is what will allow you to choose what to run.
arg is what you want to send. Usually a table with all the informations to send. All objects are not available, like player or square. Use only strings, ints or floats. So if you want to send a square for exemple, you need to send the position and then use it to get the square.

Make and init files

First you need to make one file in media/lua/client

local Commands = {}
local moduleName = "myModule"

-- Event
local onServerCommand = function(module, command, args)
    if module == moduleName and Commands[command] then
        args = args or {}
        Commands[command](args)
    end
end

Events.OnServerCommand.Add(onServerCommand)

Then one file in media/lua/server

---Server side
local Commands = {}
local moduleName = "myModule"

Commands["SendServer"] = function(player, arg)
    local otherPlayer = getPlayerByOnlineID(arg["To"])
    sendServerCommand(otherPlayer, "TOC", arg["command"], arg)
end

local onClientCommand = function(module, command, player, args)
    if module == 'TOC' and Commands[command] then
        args = args or {}
        Commands[command](_, args)
    end
end
Events.OnClientCommand.Add(onClientCommand)

From client, send a command to a player

Ok so first you make a function to call to send the data. For that, add this function in the client file.

function SendMyFunction(player, arg1, arg2, arg3)
    local arg = {};
    arg["From"] = getPlayer():getOnlineID();
    arg["To"] = player:getOnlineID();
    arg["command"] = "myFunction";
    arg["toSend"] = {arg1, arg2, arg3};
    sendClientCommand(moduleName, "SendServer", arg);
end

Then add that, it's what is call to the receiver.

Commands["myFunction"] = function(arg)
    local arg = arg["toSend"];
    -- Code here
end

And use it like that:

SendMyFunction(playerObj, "arg1", 100, {"arg2", 3, 88})

Note: You can use this as an example for send to server.

From client, request data from another client

It's the same as above but twice. Add this to the client file:

function AskMyFunction(player, arg1)
    local arg = {};
    arg["From"] = getPlayer():getOnlineID();
    arg["To"] = player:getOnlineID();
    arg["command"] = "askMyFunction";
    arg["toSend"] = arg1;
    sendClientCommand(moduleName, "SendServer", arg);
end

Commands["askMyFunction"] = function(arg)
    local arg1 = arg["toSend"];
    
    arg["To"] = arg["From"];
    arg["From"] = getPlayer():getOnlineID();
    arg["command"] = "responseMyFunction";
    arg["toSend"] = {arg1, arg2, arg3};
    sendClientCommand(moduleName, "SendServer", arg);
end

Commands["responseMyFunction"] = function(arg)
    local response = arg["toSend"]
    -- Code here
end