Simulating Bad Network Connections

This page covers how to simulate poor network conditions when testing with FishNet.

When developing a multiplayer game, it’s not enough to test only under perfect network conditions. Real-world players will often experience latency, jitter, out of order packets, and packet loss, and your game needs to tolerate these. If you only test on your local machine with a flawless connection, you risk shipping a game that breaks down as soon as it’s played online.

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What conditions affect networked games?

• Latency (Ping) — delays between sending and receiving packets.

• Jitter — variations in latency over time (unstable ping).

• Out-of-order Packets — packets may arrive out of the order from when they were sent.

• Packet Loss — some messages never arrive.

Testing with these factors early helps you tune interpolation, reconciliation, lag-compensation, and other systems. It also reveals edge cases that only show up at higher latencies (e.g., 500ms+).

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What values should I test with?

There’s no one-size-fits-all answer, but some general guidelines:

• Desktop broadband: 100–150ms latency, 1–3% packet loss

• Mobile networks: 100–300ms latency, 2–5% packet loss, plus jitter

• Stress testing: also check 500ms, 1000ms+, and extreme packet loss to ensure your game fails gracefully

Remember: don’t test with just “added delay.” Real networks get affected by multiple factors.

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FishNet’s built-in simulator

FishNet includes a basic latency simulator that can add artificial latency, packet loss, and tamper with packet order. These can also affect the client host player.

To use this, add the TransportManager component to your network manager. You will now be able to enable the Latency Simulator and tweak its settings.

The Latency Simulator on the TransportManager

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External tools

For more options it's recommended to use an external tool, such as one of the ones listed below:

• Windows: Clumsy

• macOS/iOS: Network Link Conditioner (in Apple’s Additional Tools for Xcode)

• macOS (advanced): dummynet, dnctl and pfctl (built into macOS)

• Linux: netem

These tools let you add latency, packet loss, bandwidth limits, and more. They operate at the system level, so every application (including your game) experiences the degraded connection.