diff --git a/ocaml/Block.ml b/ocaml/Block.ml
index 29c9bf8..07f7030 100644
--- a/ocaml/Block.ml
+++ b/ocaml/Block.ml
@@ -120,13 +120,17 @@ let of_bytes b =
 
 
 let to_string b =
-  Printf.sprintf "%s %s # %s %s %s %d"
-  (Sample.to_string       b.value )
-  (Weight.to_float        b.weight       |> string_of_float)
-  (Property.to_string     b.property)
-  (Compute_node.to_string b.compute_node)
-  (string_of_int          b.pid)
-  (Block_id.to_int        b.block_id)
+  if Qmcchem_config.binary_io then
+    to_bytes b
+    |> Bytes.to_string
+  else
+    Printf.sprintf "%s %s # %s %s %s %d"
+      (Sample.to_string       b.value )
+      (Weight.to_float        b.weight       |> string_of_float)
+      (Property.to_string     b.property)
+      (Compute_node.to_string b.compute_node)
+      (string_of_int          b.pid)
+      (Block_id.to_int        b.block_id)
 
 
 let dir_name = lazy(
diff --git a/ocaml/Qmcchem_config.ml b/ocaml/Qmcchem_config.ml
index ac88031..98d6820 100644
--- a/ocaml/Qmcchem_config.ml
+++ b/ocaml/Qmcchem_config.ml
@@ -8,10 +8,10 @@ let root = lazy (
 
 (* PATH environment variable as a list of strings *)
 let path =  lazy (
-  let p = 
+  let p =
     try Sys.getenv "PATH" with
     | Not_found -> failwith "PATH environment variable is not set"
-  in 
+  in
   String.split_on_char ':' p
 )
 
@@ -23,8 +23,8 @@ let full_path exe =
   | [] -> None
   | head :: tail ->
     begin
-      let fp = 
-        Filename.concat head exe 
+      let fp =
+        Filename.concat head exe
       in
       if Sys.file_exists fp then
         Some fp
@@ -82,8 +82,8 @@ let hostname = lazy (
 )
 
 
-external get_ipv4_address_for_interface : string -> string =                                  
-  "get_ipv4_address_for_interface" 
+external get_ipv4_address_for_interface : string -> string =
+  "get_ipv4_address_for_interface"
 
 
 let ip_address = lazy (
@@ -106,7 +106,7 @@ let ip_address = lazy (
       end
   | Some interface ->
         let result = get_ipv4_address_for_interface interface in
-        if String.sub result 0 5 = "error" then                                               
+        if String.sub result 0 5 = "error" then
           Printf.sprintf "Unable to use network interface %s" interface
           |> failwith
         else
@@ -115,3 +115,5 @@ let ip_address = lazy (
 
 
 
+let binary_io = false
+
diff --git a/ocaml/Qmcchem_dataserver.ml b/ocaml/Qmcchem_dataserver.ml
index c189fee..46bb208 100644
--- a/ocaml/Qmcchem_dataserver.ml
+++ b/ocaml/Qmcchem_dataserver.ml
@@ -758,7 +758,8 @@ let run ?(daemon=true) ezfio_filename =
               | Some wall ->
                 begin
                   output_string !block_channel (Block.to_string wall);
-                  output_char   !block_channel '\n';
+                  if not Qmcchem_config.binary_io then
+                    output_char   !block_channel '\n';
                 end
               | _ -> ()
             end
@@ -767,7 +768,8 @@ let run ?(daemon=true) ezfio_filename =
               if (status = Status.Running) then
                 touch_worker b.Block.compute_node b.Block.pid ;
               output_string !block_channel (Block.to_string b);
-              output_char   !block_channel '\n';
+              if not Qmcchem_config.binary_io then
+                output_char   !block_channel '\n';
               recv_log (Block.to_string b)
             end
           | Message.Test
diff --git a/ocaml/qptypes_generator.ml b/ocaml/qptypes_generator.ml
index c3d0565..3e93818 100644
--- a/ocaml/qptypes_generator.ml
+++ b/ocaml/qptypes_generator.ml
@@ -344,7 +344,7 @@ let create_ezfio_handler () =
   let lines =
     input_lines "ezfio.ml"
     (* /!\ Change when ezfio.ml changes *)
-    |> List.mapi (fun i l -> if i > 444 then Some l else None)
+    |> List.mapi (fun i l -> if i > 442 then Some l else None)
     |> List.filter (fun x -> x <> None)
     |> List.map (fun x ->
         match x with
diff --git a/scripts/create_properties_ezfio.py b/scripts/create_properties_ezfio.py
index 8b80107..e7fb388 100755
--- a/scripts/create_properties_ezfio.py
+++ b/scripts/create_properties_ezfio.py
@@ -146,6 +146,10 @@ for p in properties_qmcvar:
   print >>file, """| %(P)s -> "%(P)s" """%{'P':p[1].capitalize(), 'p':p[1]}
 print >>file, """;;
 
+let of_bytes x = 
+   Bytes.to_string x
+   |> of_string
+
 let to_bytes x = 
    to_string x
    |> Bytes.of_string