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Replecs

Verifying Your Setup

Replecs is very sensitive to how the client and server are set up. Shared components are not sent by name, they are sent as their index in the sorted list of shared components. If one side is missing a shared component, or has an extra one, every index after it shifts, and packets get decoded as the wrong components. This errors catastrophically, or worse, silently applies wrong values.

The server also never sends any information about how a component is serialized (like serdes). Replecs relies on that information being exactly the same in the client and server, so any difference in serdes or custom ids breaks reading the packet.

To catch this early, both replicators can describe their setup and compare it with the other side.

Comparing Both Sides

Section titled “Comparing Both Sides”

replicator:generate_handshake() returns a plain table describing the setup of that side: the names of every shared component, the identifiers of every registered custom id, and the bytespan and includes_variants of every serdes.

replicator:verify_handshake(info) compares that table against its own setup and returns whether they match, along with an error message describing the first mismatch it finds.

The table is safe to send through a remote, so the usual flow is to have the client send its description when it joins, and let the server verify it before doing anything else:

local replicator = require("@server/replicator")


remotes_server.verify_setup:set_callback(function(player, info)
    local ok, err = replicator:verify_handshake(info)
    if not ok then
        player:Kick(`replication setup mismatch: {err}`)
        return false
    end
    return true
end)

It works in both directions, the server can also generate its description and let the client verify it.

What Is Checked

Section titled “What Is Checked”
  • Every shared component must exist on both sides, matched by its jecs.Name.
  • Every registered custom id must exist on both sides, matched by its identifier.
  • Every serdes must exist on both sides, with the same bytespan and includes_variants.
  • Every preprocessor must exist on both sides. Only its presence is checked, not what it does.

A serdes or preprocessor set for a component the other side does not share only logs a warning.