diff --git a/src/Tiny_httpd.ml b/src/Tiny_httpd.ml
index 2ab1aa29..735ad2c8 100644
--- a/src/Tiny_httpd.ml
+++ b/src/Tiny_httpd.ml
@@ -18,6 +18,33 @@ let _debug k =
        Printf.kfprintf (fun oc -> Printf.fprintf oc "\n%!") stdout fmt)
   )
 
+let output oc s i len =
+  let fd = Unix.descr_of_out_channel oc in
+  let rec fn i len =
+    try
+      let _,w,_ = Unix.select [] [fd] [] (-1.0) in
+      if w <> [] then
+        begin
+          let written = Unix.single_write fd s i len in
+          if written < len then
+            fn (i+written) (len-written)
+        end
+      else assert false
+    with Sys_blocked_io
+       | Unix.Unix_error((EAGAIN|EWOULDBLOCK),_,_) ->
+          fn i len
+       | Unix.Unix_error(EPIPE,_,_) | Sys_error _ ->
+          ()
+  in
+  fn i len
+
+let output_string oc str =
+  let buf = Bytes.unsafe_of_string str in
+  output oc buf 0 (String.length str)
+
+let fprintf oc format =
+  Printf.ksprintf (output_string oc) format
+
 module Buf_ = struct
   type t = {
     mutable bytes: bytes;
@@ -68,13 +95,16 @@ module Byte_stream = struct
 
   exception Timeout
 
-  let of_descr_ ?(timeout=(-1.0)) ~close fd : t =
+  let of_descr_ ?(is_sock=false) ?(timeout=(-1.0)) ~close fd : t =
     let i = ref 0 in
     let len = ref 0 in
-    let size = Unix.(getsockopt_int fd SO_RCVBUF) in
+    let size = if is_sock then
+                 Unix.(getsockopt_int fd SO_RCVBUF)
+               else
+                 0x4000
+    in
     let buf = Bytes.make size ' ' in
 
-    Unix.set_nonblock fd;
     { bs_fill_buf=(fun () ->
       if !i >= !len then (
         i := 0;
@@ -97,7 +127,8 @@ module Byte_stream = struct
       bs_close=close
     }
 
-  let of_descr ?timeout fd = of_descr_ ?timeout ~close:(fun() -> Unix.close fd) fd
+  let of_descr ?timeout fd = of_descr_ ~is_sock:true ?timeout
+                               ~close:(fun() -> Unix.close fd) fd
 
   let of_chan ic =
     let fd = Unix.descr_of_in_channel ic in
@@ -656,7 +687,7 @@ module Response = struct
     while !continue do
       (* next chunk *)
       let s, i, len = str.bs_fill_buf () in
-      Printf.fprintf oc "%x\r\n" len;
+      fprintf oc "%x\r\n" len;
       output oc s i len;
       str.bs_consume len;
       if len = 0 then (
@@ -667,7 +698,7 @@ module Response = struct
     ()
 
   let output_ (oc:out_channel) (self:t) : unit =
-    Printf.fprintf oc "HTTP/1.1 %d %s\r\n" self.code (Response_code.descr self.code);
+    fprintf oc "HTTP/1.1 %d %s\r\n" self.code (Response_code.descr self.code);
     let body, is_chunked = match self.body with
       | `String s when String.length s > 1024 * 500 ->
         (* chunk-encode large bodies *)
@@ -686,7 +717,7 @@ module Response = struct
     let self = {self with headers; body} in
     _debug (fun k->k "output response: %s"
                (Format.asprintf "%a" pp {self with body=`String "<…>"}));
-    List.iter (fun (k,v) -> Printf.fprintf oc "%s: %s\r\n" k v) headers;
+    List.iter (fun (k,v) -> fprintf oc "%s: %s\r\n" k v) headers;
     output_string oc "\r\n";
     begin match body with
       | `String "" | `Void -> ()
@@ -950,11 +981,11 @@ let add_route_server_sent_handler ?accept self route f =
 
     let send_event ?event ?id ?retry ~data () : unit =
       send_response_idempotent_();
-      _opt_iter event ~f:(fun e -> Printf.fprintf oc "data: %s\n" e);
-      _opt_iter id ~f:(fun e -> Printf.fprintf oc "id: %s\n" e);
-      _opt_iter retry ~f:(fun e -> Printf.fprintf oc "retry: %s\n" e);
+      _opt_iter event ~f:(fun e -> fprintf oc "data: %s\n" e);
+      _opt_iter id ~f:(fun e -> fprintf oc "id: %s\n" e);
+      _opt_iter retry ~f:(fun e -> fprintf oc "retry: %s\n" e);
       let l = String.split_on_char '\n' data in
-      List.iter (fun s -> Printf.fprintf oc "data: %s\n" s) l;
+      List.iter (fun s -> fprintf oc "data: %s\n" s) l;
       output_string oc "\n"; (* finish group *)
       flush oc
     in
@@ -997,10 +1028,8 @@ let find_map f l =
   in aux f l
 
 let handle_client_ (self:t) (client_sock:Unix.file_descr) : unit =
-  let write_sock = Unix.dup client_sock in
   let _ = Unix.set_nonblock client_sock in
-  let _ = Unix.clear_nonblock write_sock in
-  let oc = Unix.out_channel_of_descr write_sock in
+  let oc = Unix.out_channel_of_descr client_sock in
   let buf = Buf_.create() in
   let is = Byte_stream.of_descr client_sock in
   let continue = ref true in