// the find
tylertreat/comcast
Simulating shitty network connections so you can build better systems.
Comcast is a CLI tool that injects network degradation — latency, packet loss, bandwidth throttling — into your dev machine by wrapping `tc`/`iptables` on Linux and `ipfw`/`pfctl` on BSD/macOS. It's for developers who want to test how their distributed systems behave under the kind of slow, flaky network conditions that kill real users, not just hard failures. No agent, no daemon — just a thin shell command wrapper you run before your integration tests.
The `tc netem` integration on Linux is solid and covers the full range: latency with distribution, reordering, corruption, duplication, and packet loss in one command. The `--target-addr` and `--target-port` flags let you degrade only specific traffic, so you can tank calls to your database while leaving localhost alone. The `--dry-run` flag prints the exact shell commands it would run, which means you can audit it and also learn the underlying tools. The network condition profile table in the README (GPRS, EDGE, Starlink, etc.) is genuinely useful as a quick reference for realistic test parameters.
No Windows support — the README acknowledges this but it's been 'maybe later' since 2014. The project is essentially frozen: the last real development was years ago and it only hit GitHub in 2025 because of a minor dependency bump. There's no programmatic API — you can't call this from a test harness without shelling out, which makes it awkward to integrate into automated test suites that need to toggle conditions mid-run. The codebase is ~500 lines across a handful of files with minimal test coverage, so if `tc` or `ipfw` flag behavior changes under you, there's no safety net.