Overview

Lightweight client/server messaging is provided by DedicatedServerMod.Shared.Networking.CustomMessaging. Mods can send arbitrary string payloads and subscribe to receive events without patching networking internals.

Note: This guide covers the CustomMessaging API for mod developers. For server configuration and backend selection (FishNetRpc, SteamP2P, SteamNetworkingSockets), see Messaging Backends Configuration.

Send helpers

• Server -> client: CustomMessaging.SendToClient(NetworkConnection, string command, string data = "")
• Server -> clients: CustomMessaging.BroadcastToClients(string command, string data = "")
• Client -> server: CustomMessaging.SendToServer(string command, string data = "")
• Client -> server with delivery result: CustomMessaging.TrySendToServer(string command, string data = "")
• Server -> client with endpoint queueing: CustomMessaging.SendToClientOrDeferUntilReady(...)

Payloads are strings; use JSON if you need structure.

Receive hooks

• Client side: CustomMessaging.ClientMessageReceived += (command, data) => { ... }
• Server side: CustomMessaging.ServerMessageReceived += (conn, command, data) => { ... }
• Endpoint readiness: CustomMessaging.EndpointReady += () => { ... }
• Readiness flag: CustomMessaging.IsEndpointReady

If you implement IClientMod/IServerMod, message forwarding is also exposed via OnCustomMessage(...) when ModManager wiring is active. Prefer the explicit events for connection context on server.

Server note: to receive OnCustomMessage(...) on server mods via forwarding, ensure wiring is enabled:

// Call once during init if you want OnCustomMessage to receive forwarded messages.
ModManager.EnsureServerMessageForwarding();

Example: round-trip

Client sends a request and server replies with JSON:

// Client
CustomMessaging.SendToServer("request_org_info", "");
CustomMessaging.ClientMessageReceived += (cmd, data) =>
{
    if (cmd == "org_info")
    {
        var info = JsonConvert.DeserializeObject<OrgInfo>(data);
        // Update UI.
    }
};

// Server
CustomMessaging.ServerMessageReceived += (conn, cmd, data) =>
{
    if (cmd == "request_org_info")
    {
        var payload = JsonConvert.SerializeObject(BuildOrgInfo(conn));
        CustomMessaging.SendToClient(conn, "org_info", payload);
    }
};

Best practices

• Keep command names namespaced, for example yourmod_feature_action.
• Validate server-side permissions before acting.
• Avoid large payloads; prefer small, frequent updates.
• Use OnClientPlayerReady() before sending from client to ensure messaging is ready.
• Use the generated API reference for the full event and property surface on CustomMessaging.