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Networking

Containers default to ContainerNetworkingMode.Bridged. The default WSLC bridge supports container-to-container IP traffic but not container-name DNS. None disables networking.

Managed networks and alias DNS

Both backends can create an owned bridge network:

var backend = await ContainerBackends.ResolveAsync(ct);
await using var network = await backend.CreateNetworkAsync(cancellationToken: ct);
await using var database = new ContainerBuilder(backend)
    .WithImage("redis:7")
    .WithNetwork(network.Name)
    .WithNetworkAliases("cache")
    .Build();
await database.StartAsync(ct);

Attach another container using the same backend and WithNetwork(network.Name) to reach cache:6379. Dispose containers before disposing the network. Names/aliases must not contain secrets. Network aliases require an explicit network; a named network cannot be combined with None.

Docker uses Testcontainers networks. WSLC uses the wslc CLI in the SDK-owned session because the managed SDK exposes only bridge/none settings, not network creation. This path requires wslc on PATH; the ordinary default-bridge path remains SDK-only. See Capabilities and Cancellation for timeouts and platform limits.

Host connections and IPs

  • WSLC host bindings are IPv4 loopback only. Clients should use 127.0.0.1, not localhost: IPv6-first clients, notably SQL Server clients, may not fall back.
  • Docker bindings default to 127.0.0.1; explicit PortBinding.HostAddress and TCP/UDP protocol selections are forwarded to Docker.
  • Random host ports are allocated by the runtime, never by probing for an unused port.
  • GetMappedPublicPort returns the assigned host port. TCP/HTTP readiness checks use the mapped host port on IPv4 loopback.
  • NetworkIp is read after startup for the selected network, and is null before start or without a network. Prefer explicit aliases for container-to-container traffic on managed networks.
  • Built-in module ConnectionMode.Container providers remain unimplemented; use explicit aliases and service ports to construct such connection strings.

UDP mapping remains unsupported by the WSLC public contract. Dynamic network attachment and arbitrary network drivers are not exposed by the shared API.