Debugging, testing, and profiling

Minimum topology matrix

Test each feature in:

• dedicated server + two remote clients;
• listen server + remote client;
• late join after state changed;
• leave and re-enter relevancy;
• disconnect/reconnect or respawn where supported;
• two local players if split screen is supported.

Do not accept a listen-server-only pass; the host combines authority and local control and can hide ownership defects.

Adverse network matrix

Use UE network emulation, then turn it off after each test:

• latency (NetEmulation.PktLag or a named emulation profile);
• packet loss (NetEmulation.PktLoss);
• jitter/lag variance;
• packet duplication;
• packet reordering, when compatible with the chosen lag settings.

Verify input responsiveness, correction, reliable-queue health, stale-state rejection, and eventual authoritative convergence.

Network Insights

Launch instances with networking trace enabled, for example:

-trace=net -NetTrace=1

For editor capture, add -tracehost=localhost when needed. Inspect:

• Packet Overview for timing and size;
• Packet Content for actors, properties, and RPCs;
• Net Stats for inclusive/exclusive byte cost;
• connection direction and selected connection;
• spikes during spawn, relevance changes, or UI-driven action spam.

Useful commands

• net.ActorReport: active replicated actor information.
• net.DumpRelevantActors: actors relevant on the next update.
• net.ListActorChannels: open actor channels.
• net.ForceOnePacketPerBunch: stress ordering assumptions.
• net.DormancyEnable 0/1: isolate dormancy-related failures.
• showdebug enhancedinput: inspect input before blaming RPCs.

Confirm command availability/side effects in the 5.8 console-command reference before adding to automation or shipping tooling.

Failure tree

Symptom	First checks
Server RPC never runs	caller owns actor, actor/component replicates, call made on client copy
Property only updates for owner	replication condition and actor relevancy/ownership
Works until actor sleeps	wake/flush before mutation, including component/subobject
Remote client misses effect	actor relevance at multicast time; should it be durable state?
Duplicate/late effect	RepNotify treated as a new event instead of current state
Character rubber-bands	server/client movement divergence; use CMC trace/saved moves
Bandwidth spike	high-frequency RPC/property, always-relevant actors, large collections
Only host works	local-control/authority branch conflated or wrong owner

Shipping gate

• Server remains correct with malicious/out-of-range/repeated client requests.
• All durable state reconstructs for late and re-relevant clients.
• Reliable RPC rate is bounded under worst input spam.
• Ordering assumptions survive forced packet/bunch stress.
• Network Insights meets server CPU and per-connection bandwidth budgets at target scale.
• Experimental/Beta system risks and rollback are documented.