A vibe-coded container setup that runs System.Net.Sockets.Socket.ConnectAsync tests on Linux. It uses tc to introduce artificial delay so we can simulate slow connections and define tests for Happy Eyeballs scenarios where IPv4 and IPv4 connection attempts are racing with each other.

• You have to be on Linux
• Change TESTRUNTIME in .env to point to your locally-built runtime.
• Run docker compose up --build --abort-on-container-exit from the repo root.

• The docker setup defines a testclient container and various test server containers (server-v4-fast, server-v4-slow, server-v6-fast, server-v6-slow). testclient runs Xunit tests which attempt to connect to the sockets hosted in the server containers.
• Each server is configured with tc qdisc add dev eth0 root netem delay ${DELAY}ms to delay TCP packets.
• testclient hosts a CoreDNS server to resolve predefined hostnames.
• The IP addresses and the hostnames are defined in the .env file.
• The IP addresses and the hostnames are used in TestClient/ConnectTests.cs test cases to test various (Parallel) connection behaviors.