Server Callbacks

Server callbacks are the primary way client-side code requests data from the server and receives a response in a single round-trip.

Registering a callback (server)

RP.RegisterServerCallback(name, handler)

Registers a named callback. The handler receives (source, cb, ...args) where cb must be called to send the response back to the client.

--- @param name string      Unique callback name
--- @param handler fun(src: number, cb: fun(...), ...)
RP.RegisterServerCallback('myResource:getPlayerInfo', function(src, cb, extraArg)
    local p = RP.GetPlayerFromSource(src)
    if not p then return cb(nil) end
    cb({
        pid      = p.pid,
        username = p.username,
        rank     = p:getRank(),
        xp       = p.xp,
        extra    = extraArg,
    })
end)

Triggering a callback (client)

RP.TriggerServerCallback(name, cb, ...)

Fires the named server callback and calls cb when the server responds.

--- @param name string
--- @param cb  fun(...)  Response handler
--- @vararg any          Arguments forwarded to the server handler
RP.TriggerServerCallback('myResource:getPlayerInfo', function(data)
    if not data then return end
    print('Username:', data.username)
    print('Rank:', data.rank)
end, "someExtraArg")

Full example

-- server/callbacks.lua
RP.RegisterServerCallback('shop:getBalance', function(src, cb)
    local p = RP.GetPlayerFromSource(src)
    cb(p and p.accounts['credits'] or 0)
end)
 
RP.RegisterServerCallback('shop:purchase', function(src, cb, itemId, price)
    local p = RP.GetPlayerFromSource(src)
    if not p then return cb(false, 'Not loaded') end
 
    local bal = p.accounts['credits']
    if bal < price then return cb(false, 'Insufficient funds') end
 
    p.accounts['credits'] = bal - price
    -- grant item ...
    cb(true, 'Purchase successful')
end)

How it works internally

1. Client fires _rp-base:triggerCallback net event with the callback name and a sequential numeric ID.
2. Server looks up the handler in RP._cbs and calls it with (source, respondFn, ...args).
3. respondFn fires _rp-base:callback back to the client with the same ID.
4. Client resolves the pending callback by ID and calls the user's cb.
5. If the callback name is not found the server fires back a negative ID — the client discards the pending entry cleanly.