Data Flow

Two end-to-end walkthroughs that connect the architecture pieces. Paths are under OpenSim/.

A) Viewer login (LLLogin)

1. The viewer hits Robust’s login endpoint. HTTP entry point: Server/Handlers/Login/LLLoginServiceInConnector.cs.
2. That calls into the service: Services/LLLoginService/LLLoginService.cs → LLLoginService.Login(...).
3. Inside Login (roughly):
   • Client allow/deny checks (regex on viewer name, MAC, ID0).
   • m_UserAccountService.GetUserAccount(...) – look up the account (Services/UserAccountService/).
   • m_AuthenticationService.Authenticate(...) – verify the password (Services/AuthenticationService/).
   • Duplicate-presence check via m_GridUserService.
   • Fetch inventory (m_InventoryService), friends/avatar data.
   • Ask IGridService for the destination region.
   • Build the LoginResponse: circuit code, seed capability, simulator IP/port.
4. The response returns to the viewer. The viewer then opens an LLUDP connection to the simulator and establishes an agent circuit (AgentCircuitData), handled by the client stack in Region/ClientStack/Linden/.

The simulator side of “an agent arrived” is a child or root agent represented by ScenePresence (Region/Framework/Scenes/ScenePresence.cs).

B) Agent transfer between regions (teleport / border cross)

1. EntityTransferModule (Region/CoreModules/Framework/EntityTransfer/EntityTransferModule.cs, : INonSharedRegionModule, IEntityTransferModule) handles teleport (TransferAgent) and border cross (CrossToNeighbour). It builds an AgentCircuitData and calls:
   • m_scene.SimulationService.CreateAgent(source, destination, agentCircuit, flags, ctx, out reason)
   • m_scene.SimulationService.UpdateAgent(destination, agent, ctx)
2. m_scene.SimulationService is an ISimulationService provided by a region module:
   • Local destination → LocalSimulationConnectorModule (CoreModules/ServiceConnectorsOut/Simulation/LocalSimulationConnector.cs) routes to the in-process Scene.
   • Remote destination → RemoteSimulationConnectorModule (.../RemoteSimulationConnector.cs) delegates to SimulationServiceConnector (Services/Connectors/Simulation/SimulationServiceConnector.cs), which issues HTTP agent/ REST calls to the destination simulator.
3. At the destination, Robust-style in-handlers (Server/Handlers/Simulation/AgentHandlers.cs + SimulationServiceInConnector.cs) call the destination Scene’s SimulationService.CreateAgent, creating a child agent (ScenePresence) there.
4. When the viewer connects to the destination and reports in, ReleaseAgent/CloseAgent finalize the move. Hypergrid crossings extend this via HGEntityTransferModule.cs.

Mental summary

• Login = viewer → Robust (LLLoginService) → back to viewer → LLUDP to simulator → ScenePresence.
• Teleport/cross = source Scene → EntityTransferModule → ISimulationService (local or HTTP connector) → destination Scene (ScenePresence child agent) → viewer reconnects.

Both flows show the same design: shared logic lives in Services/*Service, remote access is a Connectors/* proxy, and region-side behaviour is a CoreModules region module. See Where to look to jump straight to the code, and Protocols for the HTTP bodies those connectors send and receive (local grid and Hypergrid).