diff --git a/.github/workflows/gh-pages.yml b/.github/workflows/gh-pages.yml
new file mode 100644
index 0000000..46a599b
--- /dev/null
+++ b/.github/workflows/gh-pages.yml
@@ -0,0 +1,35 @@
+name: github pages
+
+on:
+  push:
+    branches:
+      - main # Set a branch name to trigger deployment
+
+jobs:
+  deploy:
+    name: Deploy doc
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@main
+
+      - name: Use OCaml
+        uses: ocaml/setup-ocaml@v3
+        with:
+          ocaml-compiler: '5.2'
+          dune-cache: true
+          allow-prerelease-opam: true
+
+      # temporary until it's in a release
+      - run: opam pin picos 0.6.0 -y -n
+
+      - run: opam install picos moonpool trace
+
+      - run: opam exec -- odig odoc --cache-dir=_doc/ nanoev
+
+      - name: Deploy
+        uses: peaceiris/actions-gh-pages@v3
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: ./_doc/html
+          destination_dir: .
+          enable_jekyll: false
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
new file mode 100644
index 0000000..fb8daa9
--- /dev/null
+++ b/.github/workflows/main.yml
@@ -0,0 +1,61 @@
+name: Build and Test
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+jobs:
+  run:
+    name: build  # build+test on various versions of OCaml, on linux
+    timeout-minutes: 15
+    strategy:
+      fail-fast: true
+      matrix:
+        os:
+            - ubuntu-latest
+        ocaml-compiler:
+            - '5.0'
+            - '5.3'
+
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@main
+      - name: Use OCaml ${{ matrix.ocaml-compiler }}
+        uses: ocaml/setup-ocaml@v3
+        with:
+          ocaml-compiler: ${{ matrix.ocaml-compiler }}
+          dune-cache: true
+          allow-prerelease-opam: true
+
+      - run: opam pin picos 0.6.0 -y -n
+      - run: opam install picos
+      - run: opam install -t --deps-only .
+
+      - run: opam exec -- dune build @install
+
+      # install some depopts and test deps
+      - run: opam install -t trace
+
+      - run: opam exec -- dune build --profile=release --force @install @runtest
+
+  format:
+    name: format
+    strategy:
+      matrix:
+        ocaml-compiler:
+            - '5.2'
+    runs-on: 'ubuntu-latest'
+    steps:
+      - uses: actions/checkout@main
+      - name: Use OCaml ${{ matrix.ocaml-compiler }}
+        uses: ocaml/setup-ocaml@v3
+        with:
+          ocaml-compiler: ${{ matrix.ocaml-compiler }}
+          dune-cache: true
+          allow-prerelease-opam: true
+
+      - run: opam install ocamlformat.0.26.2
+      - run: opam exec -- make format-check
+
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..1266d69
--- /dev/null
+++ b/README.md
@@ -0,0 +1,31 @@
+# nanoev
+
+A minimalistic but modular abstraction for IO event loops.
+
+The goal of this library is to provide a uniform abstraction over multiple
+system event loops, in a way that plays well with Picos.
+
+## Usage
+
+Very basic usage would look like this:
+
+```ocaml
+module EV = Nanoev_picos
+
+
+let () =
+  (* use a backend, eg. select *)
+  let ev = Nanoev_unix.create () in
+
+  (* install the backend *)
+  Nanoev_picos.setup_bg_thread ev;
+
+  (* setup a picos scheduler and use EV.read, EV.write, etc. *)
+  …
+```
+
+
+## Backends
+
+- [x] select
+- [ ] uring
diff --git a/dune-project b/dune-project
index e1d3ceb..e0cd8bb 100644
--- a/dune-project
+++ b/dune-project
@@ -1,6 +1,7 @@
 (lang dune 2.7)
 
 (name nanoev)
+
 (generate_opam_files true)
 
 (source
@@ -16,8 +17,24 @@
 
 (package
  (name nanoev)
- (synopsis "Tiny event loop around `select`")
+ (synopsis "Tiny event loop abstraction")
  (depends ocaml dune base-unix)
- (tags (unix select async)))
+ (depopts
+  (trace (>= 0.7))
+  (picos
+   (and (>= 0.5) (< 0.7))))
+ (tags
+  (unix select async)))
+
+(package
+ (name nanoev_tiny_httpd)
+ (synopsis "Use nanoev as a basis for tiny_httpd")
+ (depends
+  ocaml
+  dune
+  nanoev
+  picos
+  (tiny_httpd (>= 0.17)))
+ (tags (nanoev http)))
 
 ; See the complete stanza docs at https://dune.readthedocs.io/en/stable/reference/dune-project/index.html
diff --git a/echo.sh b/echo.sh
new file mode 100755
index 0000000..a3a0bcf
--- /dev/null
+++ b/echo.sh
@@ -0,0 +1,2 @@
+#!/bin/sh
+exec dune exec --display=quiet -- examples/echo/echo.exe $@
diff --git a/examples/echo/dune b/examples/echo/dune
new file mode 100644
index 0000000..7fa6bea
--- /dev/null
+++ b/examples/echo/dune
@@ -0,0 +1,4 @@
+(executable
+ (name echo)
+ (libraries nanoev nanoev.unix moonpool moonpool.fib trace trace-tef
+   nanoev_tiny_httpd))
diff --git a/examples/echo/echo.ml b/examples/echo/echo.ml
new file mode 100644
index 0000000..a5543b7
--- /dev/null
+++ b/examples/echo/echo.ml
@@ -0,0 +1,280 @@
+open Tiny_httpd_core
+module Log = Tiny_httpd.Log
+
+let ( let@ ) = ( @@ )
+let now_ = Unix.gettimeofday
+
+let alice_text =
+  "CHAPTER I. Down the Rabbit-Hole  Alice was beginning to get very tired of \
+   sitting by her sister on the bank, and of having nothing to do: once or \
+   twice she had peeped into the book her sister was reading, but it had no \
+   pictures or conversations in it, <and what is the use of a book,> thought \
+   Alice <without pictures or conversations?> So she was considering in her \
+   own mind (as well as she could, for the hot day made her feel very sleepy \
+   and stupid), whether the pleasure of making a daisy-chain would be worth \
+   the trouble of getting up and picking the daisies, when suddenly a White \
+   Rabbit with pink eyes ran close by her. There was nothing so very \
+   remarkable in that; nor did Alice think it so very much out of the way to \
+   hear the Rabbit say to itself, <Oh dear! Oh dear! I shall be late!> (when \
+   she thought it over afterwards, it occurred to her that she ought to have \
+   wondered at this, but at the time it all seemed quite natural); but when \
+   the Rabbit actually took a watch out of its waistcoat-pocket, and looked at \
+   it, and then hurried on, Alice started to her feet, for it flashed across \
+   her mind that she had never before seen a rabbit with either a \
+   waistcoat-pocket, or a watch to take out of it, and burning with curiosity, \
+   she ran across the field after it, and fortunately was just in time to see \
+   it pop down a large rabbit-hole under the hedge. In another moment down \
+   went Alice after it, never once considering how in the world she was to get \
+   out again. The rabbit-hole went straight on like a tunnel for some way, and \
+   then dipped suddenly down, so suddenly that Alice had not a moment to think \
+   about stopping herself before she found herself falling down a very deep \
+   well. Either the well was very deep, or she fell very slowly, for she had \
+   plenty of time as she went down to look about her and to wonder what was \
+   going to happen next. First, she tried to look down and make out what she \
+   was coming to, but it was too dark to see anything; then she looked at the \
+   sides of the well, and noticed that they were filled with cupboards......"
+
+(* util: a little middleware collecting statistics *)
+let middleware_stat () : Server.Middleware.t * (unit -> string) =
+  let n_req = ref 0 in
+  let total_time_ = ref 0. in
+  let parse_time_ = ref 0. in
+  let build_time_ = ref 0. in
+  let write_time_ = ref 0. in
+
+  let m h req ~resp =
+    incr n_req;
+    let t1 = Request.start_time req in
+    let t2 = now_ () in
+    h req ~resp:(fun response ->
+        let t3 = now_ () in
+        resp response;
+        let t4 = now_ () in
+        total_time_ := !total_time_ +. (t4 -. t1);
+        parse_time_ := !parse_time_ +. (t2 -. t1);
+        build_time_ := !build_time_ +. (t3 -. t2);
+        write_time_ := !write_time_ +. (t4 -. t3))
+  and get_stat () =
+    Printf.sprintf
+      "%d requests (average response time: %.3fms = %.3fms + %.3fms + %.3fms)"
+      !n_req
+      (!total_time_ /. float !n_req *. 1e3)
+      (!parse_time_ /. float !n_req *. 1e3)
+      (!build_time_ /. float !n_req *. 1e3)
+      (!write_time_ /. float !n_req *. 1e3)
+  in
+  m, get_stat
+
+(* ugly AF *)
+let base64 x =
+  let ic, oc = Unix.open_process "base64" in
+  output_string oc x;
+  flush oc;
+  close_out oc;
+  let r = input_line ic in
+  ignore (Unix.close_process (ic, oc));
+  r
+
+let setup_logging () =
+  Logs.set_reporter @@ Logs.format_reporter ();
+  Logs.set_level ~all:true (Some Logs.Debug)
+
+let () =
+  let@ () = Trace_tef.with_setup () in
+  Trace.set_thread_name "main";
+
+  let port_ = ref 8080 in
+  let max_conn = ref 1024 in
+  let j = ref 8 in
+  Arg.parse
+    (Arg.align
+       [
+         "--port", Arg.Set_int port_, " set port";
+         "-p", Arg.Set_int port_, " set port";
+         "-j", Arg.Set_int j, " number of threads";
+         "--debug", Arg.Unit setup_logging, " enable debug";
+         "--max-conns", Arg.Set_int max_conn, " maximum concurrent connections";
+       ])
+    (fun _ -> raise (Arg.Bad ""))
+    "echo [option]*";
+
+  let@ pool = Moonpool.Ws_pool.with_ ~num_threads:!j () in
+  let@ _runner = Moonpool_fib.main in
+
+  let ev = Nanoev_unix.create () in
+  Nanoev_picos.setup_bg_thread ev;
+
+  let server =
+    Nanoev_tiny_httpd.create ~new_thread:(Moonpool.run_async pool) ~port:!port_
+      ~max_connections:!max_conn ()
+  in
+
+  let m_stats, get_stats = middleware_stat () in
+  Server.add_middleware server ~stage:(`Stage 1) m_stats;
+
+  (* say hello *)
+  Server.add_route_handler ~meth:`GET server
+    Route.(exact "hello" @/ string @/ return)
+    (fun name _req -> Response.make_string (Ok ("hello " ^ name ^ "!\n")));
+
+  (* compressed file access *)
+  Server.add_route_handler ~meth:`GET server
+    Route.(exact "zcat" @/ string_urlencoded @/ return)
+    (fun path _req ->
+      let ic = open_in path in
+      let str = IO.Input.of_in_channel ic in
+      let mime_type =
+        try
+          let p = Unix.open_process_in (Printf.sprintf "file -i -b %S" path) in
+          try
+            let s = [ "Content-Type", String.trim (input_line p) ] in
+            ignore @@ Unix.close_process_in p;
+            s
+          with _ ->
+            ignore @@ Unix.close_process_in p;
+            []
+        with _ -> []
+      in
+      Response.make_stream ~headers:mime_type (Ok str));
+
+  (* echo request *)
+  Server.add_route_handler server
+    Route.(exact "echo" @/ return)
+    (fun req ->
+      let q =
+        Request.query req
+        |> List.map (fun (k, v) -> Printf.sprintf "%S = %S" k v)
+        |> String.concat ";"
+      in
+      Response.make_string
+        (Ok (Format.asprintf "echo:@ %a@ (query: %s)@." Request.pp req q)));
+
+  (* file upload *)
+  Server.add_route_handler_stream ~meth:`PUT server
+    Route.(exact "upload" @/ string @/ return)
+    (fun path req ->
+      Log.debug (fun k ->
+          k "start upload %S, headers:\n%s\n\n%!" path
+            (Format.asprintf "%a" Headers.pp (Request.headers req)));
+      try
+        let oc = open_out @@ "/tmp/" ^ path in
+        IO.Input.to_chan oc req.Request.body;
+        flush oc;
+        Response.make_string (Ok "uploaded file")
+      with e ->
+        Response.fail ~code:500 "couldn't upload file: %s"
+          (Printexc.to_string e));
+
+  (* protected by login *)
+  Server.add_route_handler server
+    Route.(exact "protected" @/ return)
+    (fun req ->
+      let ok =
+        match Request.get_header req "authorization" with
+        | Some v ->
+          Log.debug (fun k -> k "authenticate with %S" v);
+          v = "Basic " ^ base64 "user:foobar"
+        | None -> false
+      in
+      if ok then (
+        (* FIXME: a logout link *)
+        let s =
+          "<p>hello, this is super secret!</p><a href=\"/logout\">log out</a>"
+        in
+        Response.make_string (Ok s)
+      ) else (
+        let headers =
+          Headers.(empty |> set "www-authenticate" "basic realm=\"echo\"")
+        in
+        Response.fail ~code:401 ~headers "invalid"
+      ));
+
+  (* logout *)
+  Server.add_route_handler server
+    Route.(exact "logout" @/ return)
+    (fun _req -> Response.fail ~code:401 "logged out");
+
+  (* stats *)
+  Server.add_route_handler server
+    Route.(exact "stats" @/ return)
+    (fun _req ->
+      let stats = get_stats () in
+      Response.make_string @@ Ok stats);
+
+  Server.add_route_handler server
+    Route.(exact "alice" @/ return)
+    (fun _req -> Response.make_string (Ok alice_text));
+
+  (* main page *)
+  Server.add_route_handler server
+    Route.(return)
+    (fun _req ->
+      let open Tiny_httpd_html in
+      let h =
+        html []
+          [
+            head [] [ title [] [ txt "index of echo" ] ];
+            body []
+              [
+                h3 [] [ txt "welcome!" ];
+                p [] [ b [] [ txt "endpoints are:" ] ];
+                ul []
+                  [
+                    li [] [ pre [] [ txt "/hello/:name (GET)" ] ];
+                    li []
+                      [
+                        pre []
+                          [
+                            a [ A.href "/echo/" ] [ txt "echo" ];
+                            txt " echo back query";
+                          ];
+                      ];
+                    li []
+                      [ pre [] [ txt "/upload/:path (PUT) to upload a file" ] ];
+                    li []
+                      [
+                        pre []
+                          [
+                            txt
+                              "/zcat/:path (GET) to download a file (deflate \
+                               transfer-encoding)";
+                          ];
+                      ];
+                    li []
+                      [
+                        pre []
+                          [
+                            a [ A.href "/stats/" ] [ txt "/stats/" ];
+                            txt " (GET) to access statistics";
+                          ];
+                      ];
+                    li []
+                      [
+                        pre []
+                          [
+                            a [ A.href "/protected" ] [ txt "/protected" ];
+                            txt
+                              " (GET) to see a protected page (login: user, \
+                               password: foobar)";
+                          ];
+                      ];
+                    li []
+                      [
+                        pre []
+                          [
+                            a [ A.href "/logout" ] [ txt "/logout" ];
+                            txt " (POST) to log out";
+                          ];
+                      ];
+                  ];
+              ];
+          ]
+      in
+      let s = to_string_top h in
+      Response.make_string ~headers:[ "content-type", "text/html" ] @@ Ok s);
+
+  Printf.printf "listening on http://%s:%d\n%!" (Server.addr server)
+    (Server.port server);
+  match Server.run server with
+  | Ok () -> ()
+  | Error e -> raise e
diff --git a/nanoev.opam b/nanoev.opam
index 2981f11..9fa7ba9 100644
--- a/nanoev.opam
+++ b/nanoev.opam
@@ -1,6 +1,6 @@
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
-synopsis: "Tiny event loop around `select`"
+synopsis: "Tiny event loop abstraction"
 maintainer: ["Simon Cruanes"]
 authors: ["Simon Cruanes"]
 license: "MIT"
@@ -13,6 +13,10 @@ depends: [
   "base-unix"
   "odoc" {with-doc}
 ]
+depopts: [
+  "trace" {>= "0.7"}
+  "picos" {>= "0.5" & < "0.7"}
+]
 build: [
   ["dune" "subst"] {dev}
   [
diff --git a/nanoev_tiny_httpd.opam b/nanoev_tiny_httpd.opam
new file mode 100644
index 0000000..9504331
--- /dev/null
+++ b/nanoev_tiny_httpd.opam
@@ -0,0 +1,32 @@
+# This file is generated by dune, edit dune-project instead
+opam-version: "2.0"
+synopsis: "Use nanoev as a basis for tiny_httpd"
+maintainer: ["Simon Cruanes"]
+authors: ["Simon Cruanes"]
+license: "MIT"
+tags: ["nanoev" "http"]
+homepage: "https://github.com/c-cube/nanoev"
+bug-reports: "https://github.com/c-cube/nanoev/issues"
+depends: [
+  "ocaml"
+  "dune" {>= "2.7"}
+  "nanoev"
+  "picos"
+  "tiny_httpd" {>= "0.17"}
+  "odoc" {with-doc}
+]
+build: [
+  ["dune" "subst"] {dev}
+  [
+    "dune"
+    "build"
+    "-p"
+    name
+    "-j"
+    jobs
+    "@install"
+    "@runtest" {with-test}
+    "@doc" {with-doc}
+  ]
+]
+dev-repo: "git+https://github.com/c-cube/nanoev.git"
diff --git a/src/core/dune b/src/core/dune
new file mode 100644
index 0000000..07249b5
--- /dev/null
+++ b/src/core/dune
@@ -0,0 +1,11 @@
+(library
+ (name nanoev)
+ (public_name nanoev)
+ (synopsis "Nano ev loop")
+ (libraries
+  unix
+  (select
+   trace_.ml
+   from
+   (trace.core -> trace_.real.ml)
+   (-> trace_.dummy.ml))))
diff --git a/src/nanoev.ml b/src/core/nanoev.ml
similarity index 67%
rename from src/nanoev.ml
rename to src/core/nanoev.ml
index 00989e9..c15935e 100644
--- a/src/nanoev.ml
+++ b/src/core/nanoev.ml
@@ -1,11 +1,28 @@
+module Trace_ = Trace_
+
+exception Closed
+
 module Impl = struct
   type 'st ops = {
     clear: 'st -> unit;
     wakeup_from_outside: 'st -> unit;
+    close: 'st -> Unix.file_descr -> unit;
     on_readable:
-      'a 'b. 'st -> Unix.file_descr -> 'a -> 'b -> ('a -> 'b -> unit) -> unit;
+      'a 'b.
+      'st ->
+      Unix.file_descr ->
+      'a ->
+      'b ->
+      (closed:bool -> 'a -> 'b -> unit) ->
+      unit;
     on_writable:
-      'a 'b. 'st -> Unix.file_descr -> 'a -> 'b -> ('a -> 'b -> unit) -> unit;
+      'a 'b.
+      'st ->
+      Unix.file_descr ->
+      'a ->
+      'b ->
+      (closed:bool -> 'a -> 'b -> unit) ->
+      unit;
     run_after_s: 'a 'b. 'st -> float -> 'a -> 'b -> ('a -> 'b -> unit) -> unit;
     step: 'st -> unit;
   }
@@ -21,6 +38,7 @@ type t = Impl.t
 
 let[@inline] clear (Ev (ops, st)) = ops.clear st
 let[@inline] wakeup_from_outside (Ev (ops, st)) = ops.wakeup_from_outside st
+let[@inline] close (Ev (ops, st)) fd = ops.close st fd
 
 let[@inline] on_readable (Ev (ops, st)) fd x y f : unit =
   ops.on_readable st fd x y f
@@ -32,13 +50,3 @@ let[@inline] run_after_s (Ev (ops, st)) time x y f : unit =
   ops.run_after_s st time x y f
 
 let[@inline] step (Ev (ops, st)) : unit = ops.step st
-
-(*
-let rec read (self:t) fd buf i len : int =
-  match Unix.read fd buf i len with
-    | n -> n
-  | exception Unix.Unix_error (Unix, _, _) ->
-    read self fd buf i len
-*)
-
-
diff --git a/src/core/nanoev.mli b/src/core/nanoev.mli
new file mode 100644
index 0000000..4792cd6
--- /dev/null
+++ b/src/core/nanoev.mli
@@ -0,0 +1,58 @@
+(** Nano event loop *)
+
+type t
+
+exception Closed
+
+module Impl : sig
+  type 'st ops = {
+    clear: 'st -> unit;
+    wakeup_from_outside: 'st -> unit;
+    close: 'st -> Unix.file_descr -> unit;
+    on_readable:
+      'a 'b.
+      'st ->
+      Unix.file_descr ->
+      'a ->
+      'b ->
+      (closed:bool -> 'a -> 'b -> unit) ->
+      unit;
+    on_writable:
+      'a 'b.
+      'st ->
+      Unix.file_descr ->
+      'a ->
+      'b ->
+      (closed:bool -> 'a -> 'b -> unit) ->
+      unit;
+    run_after_s: 'a 'b. 'st -> float -> 'a -> 'b -> ('a -> 'b -> unit) -> unit;
+    step: 'st -> unit;
+  }
+
+  val build : 'a ops -> 'a -> t
+end
+
+val clear : t -> unit
+(** Reset the state *)
+
+val wakeup_from_outside : t -> unit
+
+val step : t -> unit
+(** Run one step of the event loop until something happens *)
+
+val close : t -> Unix.file_descr -> unit
+(** Close the file descriptor and clean it up *)
+
+val on_readable :
+  t -> Unix.file_descr -> 'a -> 'b -> (closed:bool -> 'a -> 'b -> unit) -> unit
+
+val on_writable :
+  t -> Unix.file_descr -> 'a -> 'b -> (closed:bool -> 'a -> 'b -> unit) -> unit
+
+val run_after_s : t -> float -> 'a -> 'b -> ('a -> 'b -> unit) -> unit
+
+(**/**)
+
+module Trace_ = Trace_
+
+(**/**)
diff --git a/src/core/trace_.dummy.ml b/src/core/trace_.dummy.ml
new file mode 100644
index 0000000..b08b984
--- /dev/null
+++ b/src/core/trace_.dummy.ml
@@ -0,0 +1,3 @@
+let[@inline] with_span ?data:_ ~__FILE__:_ ~__LINE__:_ _name f = f 0L
+let[@inline] message ?data:_ _ = ()
+let set_thread_name (_ : string) = ()
diff --git a/src/core/trace_.real.ml b/src/core/trace_.real.ml
new file mode 100644
index 0000000..6c513a5
--- /dev/null
+++ b/src/core/trace_.real.ml
@@ -0,0 +1,5 @@
+let[@inline] with_span ?data ~__FILE__ ~__LINE__ name f =
+  Trace_core.with_span ?data ~__FILE__ ~__LINE__ name f
+
+let[@inline] message ?data m = Trace_core.message ?data m
+let set_thread_name name = Trace_core.set_thread_name name
diff --git a/src/dune b/src/dune
deleted file mode 100644
index 8109e16..0000000
--- a/src/dune
+++ /dev/null
@@ -1,5 +0,0 @@
-(library
- (name nanoev)
- (public_name nanoev)
- (synopsis "Nano ev loop")
- (libraries unix))
diff --git a/src/nanoev.mli b/src/nanoev.mli
deleted file mode 100644
index fcbd0b8..0000000
--- a/src/nanoev.mli
+++ /dev/null
@@ -1,30 +0,0 @@
-(** Nano event loop *)
-
-type t
-
-module Impl : sig
-  type 'st ops = {
-    clear: 'st -> unit;
-    wakeup_from_outside: 'st -> unit;
-    on_readable:
-      'a 'b. 'st -> Unix.file_descr -> 'a -> 'b -> ('a -> 'b -> unit) -> unit;
-    on_writable:
-      'a 'b. 'st -> Unix.file_descr -> 'a -> 'b -> ('a -> 'b -> unit) -> unit;
-    run_after_s: 'a 'b. 'st -> float -> 'a -> 'b -> ('a -> 'b -> unit) -> unit;
-    step: 'st -> unit;
-  }
-
-  val build : 'a ops -> 'a -> t
-end
-
-val clear : t -> unit
-(** Reset the state *)
-
-val wakeup_from_outside : t -> unit
-
-val step : t -> unit
-(** Run one step of the event loop until something happens *)
-
-val on_readable : t -> Unix.file_descr -> 'a -> 'b -> ('a -> 'b -> unit) -> unit
-val on_writable : t -> Unix.file_descr -> 'a -> 'b -> ('a -> 'b -> unit) -> unit
-val run_after_s : t -> float -> 'a -> 'b -> ('a -> 'b -> unit) -> unit
diff --git a/src/picos/dune b/src/picos/dune
new file mode 100644
index 0000000..db9792d
--- /dev/null
+++ b/src/picos/dune
@@ -0,0 +1,5 @@
+(library
+ (name nanoev_picos)
+ (public_name nanoev.picos)
+ (optional) ; picos
+ (libraries threads picos nanoev))
diff --git a/src/picos/nanoev_picos.ml b/src/picos/nanoev_picos.ml
new file mode 100644
index 0000000..9920345
--- /dev/null
+++ b/src/picos/nanoev_picos.ml
@@ -0,0 +1,146 @@
+open struct
+  module Trace_ = Nanoev.Trace_
+
+  let ( let@ ) = ( @@ )
+end
+
+exception Closed = Nanoev.Closed
+
+module Global_ = struct
+  type st =
+    | None
+    | Some of {
+        active: bool Atomic.t;
+        nanoev: Nanoev.t;
+        th: Thread.t;
+      }
+
+  let st : st Atomic.t = Atomic.make None
+  let lock = Mutex.create ()
+
+  let with_lock lock f =
+    Mutex.lock lock;
+    match f () with
+    | exception e ->
+      Mutex.unlock lock;
+      raise e
+    | x ->
+      Mutex.unlock lock;
+      x
+
+  let bg_thread_ ~active ~evloop () : unit =
+    Trace_.set_thread_name "nanoev.picos.bg-thread";
+    while Atomic.get active do
+      Nanoev.step evloop
+    done
+
+  let[@inline] has_bg_thread () = Atomic.get st <> None
+
+  let setup_bg_thread (ev : Nanoev.t) : unit =
+    let@ () = with_lock lock in
+    (* shutdown existing thread, if any *)
+    (match Atomic.get st with
+    | Some st ->
+      Atomic.set st.active false;
+      Nanoev.wakeup_from_outside st.nanoev;
+      Thread.join st.th
+    | None -> ());
+
+    (* start new bg thread *)
+    let active = Atomic.make true in
+    Atomic.set st
+    @@ Some
+         {
+           active;
+           nanoev = ev;
+           th = Thread.create (bg_thread_ ~active ~evloop:ev) ();
+         }
+end
+
+let has_bg_thread = Global_.has_bg_thread
+let setup_bg_thread = Global_.setup_bg_thread
+
+let[@inline] get_loop_exn_ () : Nanoev.t =
+  match Atomic.get Global_.st with
+  | None -> failwith "No nanoev loop installed."
+  | Some st -> st.nanoev
+
+let[@inline] unwrap_ = function
+  | None -> ()
+  | Some (exn, bt) -> Printexc.raise_with_backtrace exn bt
+
+let retry_read_ fd f =
+  let ev = get_loop_exn_ () in
+  let[@unroll 1] rec loop () =
+    match f () with
+    | res -> res
+    | exception
+        Unix.Unix_error ((Unix.EAGAIN | Unix.EWOULDBLOCK | Unix.EINTR), _, _) ->
+      Trace_.message "read must wait";
+      let trigger = Picos.Trigger.create () in
+      let closed_r = ref false in
+      Nanoev.on_readable ev fd trigger closed_r (fun ~closed trigger closed_r ->
+          closed_r := closed;
+          Picos.Trigger.signal trigger);
+      Picos.Trigger.await trigger |> unwrap_;
+      if !closed_r then raise Closed;
+      loop ()
+  in
+  loop ()
+
+let retry_write_ fd f =
+  let ev = get_loop_exn_ () in
+  let rec loop () =
+    match f () with
+    | res -> res
+    | exception
+        Unix.Unix_error ((Unix.EAGAIN | Unix.EWOULDBLOCK | Unix.EINTR), _, _) ->
+      Trace_.message "write must wait";
+      let trigger = Picos.Trigger.create () in
+      let closed_r = ref false in
+      Nanoev.on_writable ev fd trigger closed_r (fun ~closed trigger closed_r ->
+          closed_r := closed;
+          Picos.Trigger.signal trigger);
+      Picos.Trigger.await trigger |> unwrap_;
+      if !closed_r then raise Closed;
+      loop ()
+  in
+  loop ()
+
+let read fd buf i len : int =
+  try
+    retry_read_ fd (fun () ->
+        Trace_.message "read";
+        Unix.read fd buf i len)
+  with Closed -> 0
+
+let close fd =
+  Unix.close fd;
+  let ev = get_loop_exn_ () in
+  Nanoev.close ev fd
+
+let accept fd =
+  try
+    retry_read_ fd (fun () ->
+        Trace_.message "accept";
+        Unix.accept fd)
+  with Unix.Unix_error ((Unix.ESHUTDOWN | Unix.ECONNABORTED), _, _) ->
+    raise Closed
+
+let write fd buf i len : int =
+  try
+    retry_write_ fd (fun () ->
+        Trace_.message "write";
+        Unix.write fd buf i len)
+  with Closed -> 0
+
+let connect fd addr = retry_write_ fd (fun () -> Unix.connect fd addr)
+
+let sleep t =
+  if t > 0. then (
+    let ev = get_loop_exn_ () in
+    let trigger = Picos.Trigger.create () in
+    Nanoev.run_after_s ev t trigger () (fun trigger () ->
+        Picos.Trigger.signal trigger);
+    Picos.Trigger.await trigger |> unwrap_
+  )
diff --git a/src/picos/nanoev_picos.mli b/src/picos/nanoev_picos.mli
new file mode 100644
index 0000000..ef795bb
--- /dev/null
+++ b/src/picos/nanoev_picos.mli
@@ -0,0 +1,32 @@
+(** Basic interface with picos *)
+
+val setup_bg_thread : Nanoev.t -> unit
+(** Install this event loop in a background thread *)
+
+val has_bg_thread : unit -> bool
+(** [has_bg_thread ()] is [true] iff a background thread is running a nanoev loop *)
+
+(** {2 Non blocking IO primitives} *)
+
+val read : Unix.file_descr -> bytes -> int -> int -> int
+(** Read from the non blocking FD.
+  @raise Nanoev.Closed if the FD is closed
+  @raise Unix.Unix_error for other errors *)
+
+val write : Unix.file_descr -> bytes -> int -> int -> int
+(** Write into the non blocking FD.
+  @raise Nanoev.Closed if the FD is closed
+  @raise Unix.Unix_error for other errors *)
+
+val close : Unix.file_descr -> unit
+(** Close the file descriptor
+  @raise Unix.Unix_error when it fails *)
+
+val connect : Unix.file_descr -> Unix.sockaddr -> unit
+
+val accept : Unix.file_descr -> Unix.file_descr * Unix.sockaddr
+(** Accept a connection on this fd.
+  @raise Nanoev.Closed if the FD is closed.
+  @raise Unix.Unix_error for other errors *)
+
+val sleep : float -> unit
diff --git a/src/tiny_httpd/dune b/src/tiny_httpd/dune
new file mode 100644
index 0000000..a372e9d
--- /dev/null
+++ b/src/tiny_httpd/dune
@@ -0,0 +1,10 @@
+(library
+ (name nanoev_tiny_httpd)
+ (public_name nanoev_tiny_httpd)
+ (libraries
+  threads
+  picos
+  (re_export nanoev)
+  nanoev.picos
+  (re_export iostream)
+  (re_export tiny_httpd)))
diff --git a/src/tiny_httpd/nanoev_tiny_httpd.ml b/src/tiny_httpd/nanoev_tiny_httpd.ml
new file mode 100644
index 0000000..7369fde
--- /dev/null
+++ b/src/tiny_httpd/nanoev_tiny_httpd.ml
@@ -0,0 +1,328 @@
+module TH = Tiny_httpd_core
+module EV = Nanoev_picos
+module Log = TH.Log
+module Slice = Iostream.Slice
+module Pool = TH.Pool
+module Buf = TH.Buf
+
+let unwrap_ = function
+  | None -> ()
+  | Some (exn, bt) -> Printexc.raise_with_backtrace exn bt
+
+(** Non blocking semaphore *)
+module Sem_ = struct
+  type t = {
+    mutable n: int;
+    max: int;
+    waiting: Picos.Trigger.t Queue.t;
+    mutex: Mutex.t;
+  }
+
+  let create n =
+    if n <= 0 then invalid_arg "Semaphore.create";
+    { n; max = n; mutex = Mutex.create (); waiting = Queue.create () }
+
+  let acquire self =
+    Mutex.lock self.mutex;
+    while self.n = 0 do
+      let tr = Picos.Trigger.create () in
+      Queue.push tr self.waiting;
+      Mutex.unlock self.mutex;
+      let res = Picos.Trigger.await tr in
+      unwrap_ res;
+      Mutex.lock self.mutex
+    done;
+    assert (self.n > 0);
+    self.n <- self.n - 1;
+    Mutex.unlock self.mutex
+
+  let release self =
+    Mutex.lock self.mutex;
+    self.n <- self.n + 1;
+    Option.iter Picos.Trigger.signal (Queue.take_opt self.waiting);
+    Mutex.unlock self.mutex
+
+  let num_acquired self = self.max - self.n
+end
+
+module Out = struct
+  open Iostream
+
+  class type t = Out_buf.t
+
+  class of_unix_fd ?(close_noerr = false) ~closed ~(buf : Slice.t)
+    (fd : Unix.file_descr) :
+    t =
+    object
+      inherit Out_buf.t_from_output ~bytes:buf.bytes ()
+
+      method private output_underlying bs i len0 =
+        let i = ref i in
+        let len = ref len0 in
+        while !len > 0 do
+          match EV.write fd bs !i !len with
+          | 0 -> failwith "write failed"
+          | n ->
+            i := !i + n;
+            len := !len - n
+          | exception
+              Unix.Unix_error
+                ( (( Unix.EBADF | Unix.ENOTCONN | Unix.ESHUTDOWN
+                   | Unix.ECONNRESET | Unix.EPIPE ) as err),
+                  fn,
+                  _ ) ->
+            failwith
+            @@ Printf.sprintf "write failed in %s: %s" fn
+                 (Unix.error_message err)
+        done
+
+      method private close_underlying () =
+        if not (Atomic.exchange closed true) then
+          if close_noerr then (
+            try EV.close fd with _ -> ()
+          ) else
+            EV.close fd
+    end
+end
+
+module In = struct
+  open Iostream
+
+  class type t = In_buf.t
+
+  let of_unix_fd ?(close_noerr = false) ~closed ~(buf : Slice.t)
+      (fd : Unix.file_descr) : t =
+    let eof = ref false in
+    object
+      inherit Iostream.In_buf.t_from_refill ~bytes:buf.bytes ()
+
+      method private refill (slice : Slice.t) =
+        if not !eof then (
+          slice.off <- 0;
+          let continue = ref true in
+          while !continue do
+            match EV.read fd slice.bytes 0 (Bytes.length slice.bytes) with
+            | n ->
+              slice.len <- n;
+              continue := false
+            | exception
+                Unix.Unix_error
+                  ( ( Unix.EBADF | Unix.ENOTCONN | Unix.ESHUTDOWN
+                    | Unix.ECONNRESET | Unix.EPIPE ),
+                    _,
+                    _ ) ->
+              eof := true;
+              continue := false
+          done;
+          (* Printf.eprintf "read returned %d B\n%!" !n; *)
+          if slice.len = 0 then eof := true
+        )
+
+      method close () =
+        if not (Atomic.exchange closed true) then (
+          eof := true;
+          if close_noerr then (
+            try EV.close fd with _ -> ()
+          ) else
+            EV.close fd
+        )
+    end
+end
+
+module Unix_tcp_server_ = struct
+  let get_addr_ sock =
+    match Unix.getsockname sock with
+    | Unix.ADDR_INET (addr, port) -> addr, port
+    | _ -> invalid_arg "httpd: address is not INET"
+
+  type t = {
+    addr: string;
+    port: int;
+    buf_pool: Buf.t Pool.t;
+    slice_pool: Slice.t Pool.t;
+    max_connections: int;
+    sem_max_connections: Sem_.t;
+        (** semaphore to restrict the number of active concurrent connections *)
+    mutable sock: Unix.file_descr option;  (** Socket *)
+    new_thread: (unit -> unit) -> unit;
+    timeout: float;
+    masksigpipe: bool;
+    mutable running: bool; (* TODO: use an atomic? *)
+  }
+
+  let shutdown_silent_ fd =
+    try Unix.shutdown fd Unix.SHUTDOWN_ALL with _ -> ()
+
+  let close_silent_ fd = try Unix.close fd with _ -> ()
+
+  let to_tcp_server (self : t) : TH.IO.TCP_server.builder =
+    {
+      TH.IO.TCP_server.serve =
+        (fun ~after_init ~handle () : unit ->
+          if self.masksigpipe && not Sys.win32 then
+            ignore (Unix.sigprocmask Unix.SIG_BLOCK [ Sys.sigpipe ] : _ list);
+          let sock, should_bind =
+            match self.sock with
+            | Some s ->
+              s, false
+              (* Because we're getting a socket from the caller (e.g. systemd) *)
+            | None ->
+              let s =
+                Unix.socket
+                  (if TH.Util.is_ipv6_str self.addr then
+                     Unix.PF_INET6
+                   else
+                     Unix.PF_INET)
+                  Unix.SOCK_STREAM 0
+              in
+              s, true (* Because we're creating the socket ourselves *)
+          in
+          Unix.set_nonblock sock;
+          Unix.setsockopt_optint sock Unix.SO_LINGER None;
+          if should_bind then (
+            let inet_addr = Unix.inet_addr_of_string self.addr in
+            Unix.setsockopt sock Unix.SO_REUSEADDR true;
+            Unix.bind sock (Unix.ADDR_INET (inet_addr, self.port));
+            let n_listen = 2 * self.max_connections in
+            Unix.listen sock n_listen
+          );
+
+          self.sock <- Some sock;
+
+          let tcp_server =
+            {
+              TH.IO.TCP_server.stop = (fun () -> self.running <- false);
+              running = (fun () -> self.running);
+              active_connections =
+                (fun () -> Sem_.num_acquired self.sem_max_connections);
+              endpoint =
+                (fun () ->
+                  let addr, port = get_addr_ sock in
+                  Unix.string_of_inet_addr addr, port);
+            }
+          in
+          after_init tcp_server;
+
+          (* how to handle a single client *)
+          let handle_client_ (client_sock : Unix.file_descr)
+              (client_addr : Unix.sockaddr) : unit =
+            Log.debug (fun k ->
+                k "t[%d]: serving new client on %s"
+                  (Thread.id @@ Thread.self ())
+                  (TH.Util.show_sockaddr client_addr));
+
+            if self.masksigpipe && not Sys.win32 then
+              ignore (Unix.sigprocmask Unix.SIG_BLOCK [ Sys.sigpipe ] : _ list);
+            Unix.set_nonblock client_sock;
+            Unix.setsockopt client_sock Unix.TCP_NODELAY true;
+            Unix.(setsockopt_float client_sock SO_RCVTIMEO self.timeout);
+            Unix.(setsockopt_float client_sock SO_SNDTIMEO self.timeout);
+
+            Pool.with_resource self.slice_pool @@ fun ic_buf ->
+            Pool.with_resource self.slice_pool @@ fun oc_buf ->
+            let closed = Atomic.make false in
+
+            let oc =
+              new Out.of_unix_fd
+                ~close_noerr:true ~closed ~buf:oc_buf client_sock
+            in
+            let ic =
+              In.of_unix_fd ~close_noerr:true ~closed ~buf:ic_buf client_sock
+            in
+            handle.handle ~client_addr ic oc
+          in
+
+          Unix.set_nonblock sock;
+          while self.running do
+            match EV.accept sock with
+            | client_sock, client_addr ->
+              (* limit concurrency *)
+              Sem_.acquire self.sem_max_connections;
+              (* Block INT/HUP while cloning to avoid children handling them.
+                 When thread gets them, our Unix.accept raises neatly. *)
+              if not Sys.win32 then
+                ignore Unix.(sigprocmask SIG_BLOCK Sys.[ sigint; sighup ]);
+              self.new_thread (fun () ->
+                  try
+                    handle_client_ client_sock client_addr;
+                    Log.debug (fun k ->
+                        k "t[%d]: done with client on %s, exiting"
+                          (Thread.id @@ Thread.self ())
+                        @@ TH.Util.show_sockaddr client_addr);
+                    shutdown_silent_ client_sock;
+                    close_silent_ client_sock;
+                    Sem_.release self.sem_max_connections
+                  with e ->
+                    let bt = Printexc.get_raw_backtrace () in
+                    shutdown_silent_ client_sock;
+                    close_silent_ client_sock;
+                    Sem_.release self.sem_max_connections;
+                    Log.error (fun k ->
+                        k
+                          "@[<v>Handler: uncaught exception for client %s:@ \
+                           %s@ %s@]"
+                          (TH.Util.show_sockaddr client_addr)
+                          (Printexc.to_string e)
+                          (Printexc.raw_backtrace_to_string bt)));
+              if not Sys.win32 then
+                ignore Unix.(sigprocmask SIG_UNBLOCK Sys.[ sigint; sighup ])
+            | exception e ->
+              Log.error (fun k ->
+                  k "Unix.accept raised an exception: %s" (Printexc.to_string e))
+          done;
+
+          (* Wait for all threads to be done: this only works if all threads are done. *)
+          Unix.close sock;
+          (* TODO? *)
+          (* Sem_.acquire self.sem_max_connections.max self.sem_max_connections; *)
+          ());
+    }
+end
+
+open struct
+  let get_max_connection_ ?(max_connections = 2048) () : int =
+    let max_connections = max 4 max_connections in
+    max_connections
+
+  let clear_slice (slice : Slice.t) =
+    Bytes.fill slice.bytes 0 (Bytes.length slice.bytes) '\x00';
+    slice.off <- 0;
+    slice.len <- 0
+end
+
+let create ?(masksigpipe = not Sys.win32) ?max_connections ?(timeout = 0.0)
+    ?buf_size ?(get_time_s = Unix.gettimeofday) ?(addr = "127.0.0.1")
+    ?(port = 8080) ?sock ?middlewares ~new_thread () : TH.Server.t =
+  let max_connections = get_max_connection_ ?max_connections () in
+  let server =
+    {
+      Unix_tcp_server_.addr;
+      new_thread;
+      buf_pool =
+        Pool.create ~clear:Buf.clear_and_zero
+          ~mk_item:(fun () -> Buf.create ?size:buf_size ())
+          ();
+      slice_pool =
+        Pool.create ~clear:clear_slice
+          ~mk_item:
+            (let buf_size = Option.value buf_size ~default:4096 in
+             fun () -> Slice.create buf_size)
+          ();
+      running = true;
+      port;
+      sock;
+      max_connections;
+      sem_max_connections = Sem_.create max_connections;
+      masksigpipe;
+      timeout;
+    }
+  in
+  let tcp_server_builder = Unix_tcp_server_.to_tcp_server server in
+  let module B = struct
+    let init_addr () = addr
+    let init_port () = port
+    let get_time_s = get_time_s
+    let tcp_server () = tcp_server_builder
+  end in
+  let backend = (module B : TH.Server.IO_BACKEND) in
+  TH.Server.create_from ?buf_size ?middlewares ~backend ()
diff --git a/src/tiny_httpd/nanoev_tiny_httpd.mli b/src/tiny_httpd/nanoev_tiny_httpd.mli
new file mode 100644
index 0000000..f0cd9af
--- /dev/null
+++ b/src/tiny_httpd/nanoev_tiny_httpd.mli
@@ -0,0 +1,15 @@
+module TH = Tiny_httpd_core
+
+val create :
+  ?masksigpipe:bool ->
+  ?max_connections:int ->
+  ?timeout:float ->
+  ?buf_size:int ->
+  ?get_time_s:(unit -> float) ->
+  ?addr:string ->
+  ?port:int ->
+  ?sock:Unix.file_descr ->
+  ?middlewares:([ `Encoding | `Stage of int ] * TH.Server.Middleware.t) list ->
+  new_thread:((unit -> unit) -> unit) ->
+  unit ->
+  TH.Server.t
diff --git a/src/unix/nanoev_unix.ml b/src/unix/nanoev_unix.ml
index 5c29cf6..7d656c1 100644
--- a/src/unix/nanoev_unix.ml
+++ b/src/unix/nanoev_unix.ml
@@ -1,12 +1,14 @@
-(* module type BACKEND = Intf.BACKEND *)
+open struct
+  module Trace_ = Nanoev.Trace_
 
-let ( let@ ) = ( @@ )
-let now_ : unit -> float = Unix.gettimeofday
+  let ( let@ ) = ( @@ )
+  let now_ : unit -> float = Unix.gettimeofday
+end
 
 (** Callback list *)
 type cbs =
   | Nil
-  | Sub : 'a * 'b * ('a -> 'b -> unit) * cbs -> cbs
+  | Sub : 'a * 'b * (closed:bool -> 'a -> 'b -> unit) * cbs -> cbs
 
 let[@inline] cb_is_empty = function
   | Nil -> true
@@ -42,6 +44,18 @@ type st = {
   lock: Mutex.t;
 }
 
+let rec perform_cbs ~closed = function
+  | Nil -> ()
+  | Sub (x, y, f, tail) ->
+    f ~closed x y;
+    perform_cbs ~closed tail
+
+let rec perform_cbs_closed ~closed = function
+  | Nil -> ()
+  | Sub (x, y, f, tail) ->
+    f ~closed x y;
+    perform_cbs_closed ~closed tail
+
 let leq_timer (Timer a) (Timer b) = a.deadline <= b.deadline
 
 let create_st () : st =
@@ -80,10 +94,12 @@ let clear (self : st) =
   ()
 
 let wakeup_from_outside (self : st) : unit =
-  if not (Atomic.exchange self.wakeup_triggered true) then (
+  if not (Atomic.exchange self.wakeup_triggered true) then
+    let@ _sp =
+      Trace_.with_span ~__FILE__ ~__LINE__ "nanoev.wakeup-from-outside"
+    in
     let b = Bytes.make 1 '!' in
     ignore (Unix.write self.wakeup_wr b 0 1 : int)
-  )
 
 let get_fd_ (self : st) fd : per_fd =
   match Hashtbl.find self.fds fd with
@@ -93,7 +109,27 @@ let get_fd_ (self : st) fd : per_fd =
     Hashtbl.add self.fds fd per_fd;
     per_fd
 
+let close self fd : unit =
+  let@ _sp = Trace_.with_span ~__FILE__ ~__LINE__ "nanoev.close" in
+  let r, w =
+    let@ self = with_lock_ self in
+    match Hashtbl.find self.fds fd with
+    | per_fd ->
+      Hashtbl.remove self.fds fd;
+      self.sub_up_to_date <- false;
+      if Atomic.get self.in_select then wakeup_from_outside self;
+      per_fd.r, per_fd.w
+    | exception Not_found ->
+      invalid_arg "File descriptor is not known to Nanoev"
+  in
+
+  (* call callbacks outside of the lock *)
+  perform_cbs_closed ~closed:true r;
+  perform_cbs_closed ~closed:true w;
+  ()
+
 let on_readable self fd x y f : unit =
+  let@ _sp = Trace_.with_span ~__FILE__ ~__LINE__ "nanoev.on-readable" in
   let@ self = with_lock_ self in
   let per_fd = get_fd_ self fd in
   per_fd.r <- Sub (x, y, f, per_fd.r);
@@ -101,6 +137,7 @@ let on_readable self fd x y f : unit =
   if Atomic.get self.in_select then wakeup_from_outside self
 
 let on_writable self fd x y f : unit =
+  let@ _sp = Trace_.with_span ~__FILE__ ~__LINE__ "nanoev.on-writable" in
   let@ self = with_lock_ self in
   let per_fd = get_fd_ self fd in
   per_fd.w <- Sub (x, y, f, per_fd.w);
@@ -108,6 +145,7 @@ let on_writable self fd x y f : unit =
   if Atomic.get self.in_select then wakeup_from_outside self
 
 let run_after_s self time x y f : unit =
+  let@ _sp = Trace_.with_span ~__FILE__ ~__LINE__ "nanoev.run-after-s" in
   let@ self = with_lock_ self in
   let deadline = now_ () +. time in
   Heap.insert self.timer (Timer { deadline; x; y; f });
@@ -115,6 +153,7 @@ let run_after_s self time x y f : unit =
 
 let recompute_if_needed (self : st) =
   if not self.sub_up_to_date then (
+    let@ _sp = Trace_.with_span ~__FILE__ ~__LINE__ "recompute-if-needed" in
     self.sub_up_to_date <- true;
     self.sub_r <- [];
     self.sub_w <- [];
@@ -132,13 +171,8 @@ let next_deadline_ (self : st) : float option =
   | exception Heap.Empty -> None
   | Timer t -> Some t.deadline
 
-let rec perform_cbs = function
-  | Nil -> ()
-  | Sub (x, y, f, tail) ->
-    f x y;
-    perform_cbs tail
-
 let step (self : st) : unit =
+  let@ _sp = Trace_.with_span ~__FILE__ ~__LINE__ "nanoev.unix.step" in
   (* gather the subscriptions and timeout *)
   let timeout, sub_r, sub_w =
     let@ self = with_lock_ self in
@@ -154,6 +188,14 @@ let step (self : st) : unit =
   (* enter [select] *)
   Atomic.set self.in_select true;
   let r_reads, r_writes, _ =
+    let@ _sp =
+      Trace_.with_span ~__FILE__ ~__LINE__ "select" ~data:(fun () ->
+          [
+            "timeout", `Float timeout;
+            "reads", `Int (List.length sub_r);
+            "writes", `Int (List.length sub_w);
+          ])
+    in
     Unix.select (self.wakeup_rd :: sub_r) sub_w [] timeout
   in
   Atomic.set self.in_select false;
@@ -176,8 +218,10 @@ let step (self : st) : unit =
 
    List.iter
      (fun fd ->
-       let per_fd = Hashtbl.find self.fds fd in
-       ready_r := per_fd :: !ready_r)
+       if fd != self.wakeup_rd then (
+         let per_fd = Hashtbl.find self.fds fd in
+         ready_r := per_fd :: !ready_r
+       ))
      r_reads;
    List.iter
      (fun fd ->
@@ -188,19 +232,27 @@ let step (self : st) : unit =
   (* call callbacks *)
   List.iter
     (fun fd ->
-      perform_cbs fd.r;
+      perform_cbs ~closed:false fd.r;
       fd.r <- Nil)
     !ready_r;
   List.iter
     (fun fd ->
-      perform_cbs fd.w;
+      perform_cbs ~closed:false fd.w;
       fd.w <- Nil)
     !ready_w;
 
   ()
 
 let ops : st Nanoev.Impl.ops =
-  { step; on_readable; on_writable; run_after_s; wakeup_from_outside; clear }
+  {
+    step;
+    close;
+    on_readable;
+    on_writable;
+    run_after_s;
+    wakeup_from_outside;
+    clear;
+  }
 
 include Nanoev
 
diff --git a/tests/unix/dune b/tests/unix/dune
index 8679c90..3ee6379 100644
--- a/tests/unix/dune
+++ b/tests/unix/dune
@@ -1,4 +1,3 @@
-
 (tests
-  (names t1)
-  (libraries nanoev nanoev.unix threads))
+ (names t1)
+ (libraries nanoev nanoev.unix threads))
diff --git a/tests/unix/t1.ml b/tests/unix/t1.ml
index 79e76ff..810087d 100644
--- a/tests/unix/t1.ml
+++ b/tests/unix/t1.ml
@@ -15,7 +15,11 @@ let () =
   let ev = E.create () in
   ignore (Thread.create loop ev : Thread.t);
   let rd, wr = mkpipe () in
-  E.on_readable ev rd () () (fun () () -> print_endline "can read");
+  E.on_readable ev rd () () (fun ~closed () () ->
+      if closed then
+        print_endline "closed!"
+      else
+        print_endline "can read");
   Thread.delay 0.05;
   print_endline "writing";
   ignore