C++ Ex Opcodes

[Ascuas Funkeln]

Hello, did someoe can explain me (Handicap Mode) how to use this?
0.3.6 V8, i patched extended opcodes by BeniS thread. And now i want link some stuff with using it.
And there is problem.
Example make visible vocation name in skill window.

Spoiler: Client Side

function onVocationChange(localPlayer, value)
  local protocolGame = g_game.getProtocolGame()
  if protocolGame then
    protocolGame:sendExtendedOpcode(51, 'class')
    return true
    end
end

Spoiler: Server Side

function onExtendedOpcode(player, opcode, buffer)
    if opcode == 51 then
    if buffer == 'class' then
        getPlayerVocationName(cid)
    return
        end
    end
end

1. How this connect work?
2. How to setup this connecting properly?
3. How to setup that client receive "target information(like vocation name)", its should be return via "buffer"?
4. There is no "receive"?
5. Did someone can show me one working extended opcode connection(not this basic language), then i think i will understand this.
I want to link this \/ xD

Spoiler: Picture

 

[Togu]

I need help on understanding opcodes too.