diff --git a/src/Tiny_httpd.ml b/src/Tiny_httpd.ml
index 87e7890b..5213ef34 100644
--- a/src/Tiny_httpd.ml
+++ b/src/Tiny_httpd.ml
@@ -4,3 +4,4 @@ include Tiny_httpd_server
 module Util = Tiny_httpd_util
 module Dir = Tiny_httpd_dir
 module Html = Tiny_httpd_html
+module IO = Tiny_httpd_io
diff --git a/src/Tiny_httpd.mli b/src/Tiny_httpd.mli
index e7385567..607d7461 100644
--- a/src/Tiny_httpd.mli
+++ b/src/Tiny_httpd.mli
@@ -85,6 +85,10 @@ module Buf = Tiny_httpd_buf
 
 module Byte_stream = Tiny_httpd_stream
 
+(** {2 IO Abstraction} *)
+
+module IO = Tiny_httpd_io
+
 (** {2 Main Server Type} *)
 
 (** @inline *)
diff --git a/src/Tiny_httpd_io.ml b/src/Tiny_httpd_io.ml
new file mode 100644
index 00000000..8d36a2a4
--- /dev/null
+++ b/src/Tiny_httpd_io.ml
@@ -0,0 +1,85 @@
+(** IO abstraction.
+
+    We abstract IO so we can support classic unix blocking IOs
+    with threads, and modern async IO with Eio.
+
+    {b NOTE}: experimental.
+
+    @since NEXT_RELEASE
+*)
+
+module In_channel = struct
+  type t = {
+    input: bytes -> int -> int -> int;
+        (** Read into the slice. Returns [0] only if the
+        channel is closed. *)
+    close: unit -> unit;
+  }
+
+  let of_in_channel ?(close_noerr = false) (ic : in_channel) : t =
+    {
+      input = (fun buf i len -> input ic buf i len);
+      close =
+        (fun () ->
+          if close_noerr then
+            close_in_noerr ic
+          else
+            close_in ic);
+    }
+
+  let of_unix_fd ?(close_noerr = false) (fd : Unix.file_descr) : t =
+    {
+      input = (fun buf i len -> Unix.read fd buf i len);
+      close =
+        (fun () ->
+          if close_noerr then (
+            try Unix.close fd with _ -> ()
+          ) else
+            Unix.close fd);
+    }
+
+  let[@inline] input (self : t) buf i len = self.input buf i len
+  let[@inline] close self : unit = self.close ()
+end
+
+module Out_channel = struct
+  type t = {
+    output: bytes -> int -> int -> unit;  (** Output slice *)
+    flush: unit -> unit;  (** Flush underlying buffer *)
+    close: unit -> unit;
+  }
+
+  let of_out_channel ?(close_noerr = false) (oc : out_channel) : t =
+    {
+      output = (fun buf i len -> output oc buf i len);
+      flush = (fun () -> flush oc);
+      close =
+        (fun () ->
+          if close_noerr then
+            close_out_noerr oc
+          else
+            close_out oc);
+    }
+
+  let[@inline] output (self : t) buf i len : unit = self.output buf i len
+
+  let[@inline] output_string (self : t) (str : string) : unit =
+    self.output (Bytes.unsafe_of_string str) 0 (String.length str)
+
+  let[@inline] close self : unit = self.close ()
+end
+
+(** A TCP server abstraction *)
+module TCP_server = struct
+  type conn_handler = {
+    handle: In_channel.t -> Out_channel.t -> unit;
+        (** Handle client connection *)
+  }
+
+  type t = {
+    listen: handle:conn_handler -> unit -> unit;
+        (** Blocking call to start listening for incoming connections.
+            Uses the connection handler to handle individual client connections. *)
+    endpoint: unit -> Unix.inet_addr * int;  (** Endpoint we listen on *)
+  }
+end
diff --git a/src/Tiny_httpd_stream.ml b/src/Tiny_httpd_stream.ml
index 66ce7aa3..3a100ebf 100644
--- a/src/Tiny_httpd_stream.ml
+++ b/src/Tiny_httpd_stream.ml
@@ -1,4 +1,5 @@
 module Buf = Tiny_httpd_buf
+module IO = Tiny_httpd_io
 
 let spf = Printf.sprintf
 
@@ -45,37 +46,32 @@ let make ?(bs = Bytes.create @@ (16 * 1024)) ?(close = ignore) ~consume ~fill ()
   in
   self
 
-let of_chan_ ?(buf_size = 16 * 1024) ~close ic : t =
+let of_input ?(buf_size = 16 * 1024) (ic : IO.In_channel.t) : t =
   make ~bs:(Bytes.create buf_size)
-    ~close:(fun _ -> close ic)
+    ~close:(fun _ -> IO.In_channel.close ic)
     ~consume:(fun self n ->
       self.off <- self.off + n;
       self.len <- self.len - n)
     ~fill:(fun self ->
       if self.off >= self.len then (
         self.off <- 0;
-        self.len <- input ic self.bs 0 (Bytes.length self.bs)
+        self.len <- IO.In_channel.input ic self.bs 0 (Bytes.length self.bs)
       ))
     ()
 
-let of_chan = of_chan_ ~close:close_in
-let of_chan_close_noerr = of_chan_ ~close:close_in_noerr
+let of_chan_ ?buf_size ic ~close_noerr : t =
+  let inc = IO.In_channel.of_in_channel ~close_noerr ic in
+  of_input ?buf_size inc
 
-let of_fd_ ?(buf_size = 16 * 1024) ~close ic : t =
-  make ~bs:(Bytes.create buf_size)
-    ~close:(fun _ -> close ic)
-    ~consume:(fun self n ->
-      self.off <- self.off + n;
-      self.len <- self.len - n)
-    ~fill:(fun self ->
-      if self.off >= self.len then (
-        self.off <- 0;
-        self.len <- Unix.read ic self.bs 0 (Bytes.length self.bs)
-      ))
-    ()
+let of_chan ?buf_size ic = of_chan_ ?buf_size ic ~close_noerr:false
+let of_chan_close_noerr ?buf_size ic = of_chan_ ?buf_size ic ~close_noerr:true
 
-let of_fd = of_fd_ ~close:Unix.close
-let of_fd_close_noerr = of_fd_ ~close:(fun f -> try Unix.close f with _ -> ())
+let of_fd_ ?buf_size ~close_noerr ic : t =
+  let inc = IO.In_channel.of_unix_fd ~close_noerr ic in
+  of_input ?buf_size inc
+
+let of_fd ?buf_size fd : t = of_fd_ ?buf_size ~close_noerr:false fd
+let of_fd_close_noerr ?buf_size fd : t = of_fd_ ?buf_size ~close_noerr:true fd
 
 let rec iter f (self : t) : unit =
   self.fill_buf ();
@@ -90,6 +86,9 @@ let rec iter f (self : t) : unit =
 let to_chan (oc : out_channel) (self : t) =
   iter (fun s i len -> output oc s i len) self
 
+let to_chan' (oc : IO.Out_channel.t) (self : t) =
+  iter (fun s i len -> IO.Out_channel.output oc s i len) self
+
 let of_bytes ?(i = 0) ?len (bs : bytes) : t =
   (* invariant: !i+!len is constant *)
   let len =
@@ -298,19 +297,22 @@ let read_chunked ?(buf = Buf.create ()) ~fail (bs : t) : t =
       refill := false)
     ()
 
-(* print a stream as a series of chunks *)
-let output_chunked (oc : out_channel) (self : t) : unit =
+let output_chunked' (oc : IO.Out_channel.t) (self : t) : unit =
   let continue = ref true in
   while !continue do
     (* next chunk *)
     self.fill_buf ();
     let n = self.len in
-    Printf.fprintf oc "%x\r\n" n;
-    output oc self.bs self.off n;
+    IO.Out_channel.output_string oc (Printf.sprintf "%x\r\n" n);
+    IO.Out_channel.output oc self.bs self.off n;
     self.consume n;
     if n = 0 then continue := false;
-    output_string oc "\r\n"
+    IO.Out_channel.output_string oc "\r\n"
   done;
   (* write another crlf after the stream (see #56) *)
-  output_string oc "\r\n";
+  IO.Out_channel.output_string oc "\r\n";
   ()
+
+(* print a stream as a series of chunks *)
+let output_chunked (oc : out_channel) (self : t) : unit =
+  output_chunked' (IO.Out_channel.of_out_channel oc) self
diff --git a/src/Tiny_httpd_stream.mli b/src/Tiny_httpd_stream.mli
index b2966662..4fc7dbcd 100644
--- a/src/Tiny_httpd_stream.mli
+++ b/src/Tiny_httpd_stream.mli
@@ -36,6 +36,10 @@ val close : t -> unit
 val empty : t
 (** Stream with 0 bytes inside *)
 
+val of_input : ?buf_size:int -> Tiny_httpd_io.In_channel.t -> t
+(** Make a buffered stream from the given channel.
+    @since NEXT_RELEASE *)
+
 val of_chan : ?buf_size:int -> in_channel -> t
 (** Make a buffered stream from the given channel. *)
 
@@ -62,6 +66,10 @@ val to_chan : out_channel -> t -> unit
 (** Write the stream to the channel.
     @since 0.3 *)
 
+val to_chan' : Tiny_httpd_io.Out_channel.t -> t -> unit
+(** Write to the IO channel.
+    @since NEXT_RELEASE *)
+
 val make :
   ?bs:bytes ->
   ?close:(t -> unit) ->
@@ -111,3 +119,7 @@ val read_exactly :
 
 val output_chunked : out_channel -> t -> unit
 (** Write the stream into the channel, using the chunked encoding. *)
+
+val output_chunked' : Tiny_httpd_io.Out_channel.t -> t -> unit
+(** Write the stream into the channel, using the chunked encoding.
+    @since NEXT_RELEASE *)