# ServerSocket A listening TCP server socket built on a non-blocking file descriptor and an [`EventLoop`](/documentation/Event/EventLoop). ``` final class ServerSocket ``` ## Overview `ServerSocket` represents a socket that has already been `bind(2)`-ed to a local address and `listen(2)`-ed on. It accepts incoming client connections through two ergonomic shapes: - ``doc://Event/documentation/Event/ServerSocket/accept()`` — awaits exactly one incoming connection and returns a connected ``doc://Event/documentation/Event/Socket``. Use this when your protocol is request/response and you want explicit control over when to service the next connection. - ``doc://Event/documentation/Event/ServerSocket/connections`` — an `AsyncThrowingStream` that yields each accepted `Socket` as it arrives, until the stream is cancelled or errors. Use this for server loops like `for try await client in server.connections { ... }`. Construct a `ServerSocket` via [`listen(port:backlog:loop:)`](/documentation/Event/Socket/listen(port:backlog:loop:)) or [`listen(on:backlog:loop:)`](/documentation/Event/Socket/listen(on:backlog:loop:)); direct construction is not part of the public API. ### Cancellation The `connections` stream does **not** currently propagate `Task` cancellation down into the outstanding `accept` event registration. Cancelling the owning task terminates the `for-try-await` loop in your code but leaves the libevent callback registered until the next activity or until the `ServerSocket` is deallocated. Workarounds: call [`close()`](/documentation/Event/ServerSocket/close()) explicitly to tear down the listener, or drop the last strong reference so `deinit` runs. See [Production Considerations](/documentation/Event/ProductionConsiderations). ### Concurrency Marked `@unchecked Sendable` to permit handoff of ownership across task boundaries. Concurrent `accept()` calls or simultaneous iteration of [`connections`](/documentation/Event/ServerSocket/connections) from multiple tasks are **undefined behavior** — libevent state is not locked, and the stored descriptor is closed unilaterally in `deinit`. The single-owner-per-scope discipline from [Production Considerations](/documentation/Event/ProductionConsiderations) applies.