diff --git a/BUILD.gn b/BUILD.gn
index 6b1d5d17b4..848dc6a59a 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -2,6 +2,7 @@
 import("//third_party/v8/gni/v8.gni")
 import("//third_party/v8/snapshot_toolchain.gni")
 import("//build_extra/flatbuffers/flatbuffer.gni")
+import("//build_extra/flatbuffers/rust/rust_flatbuffer.gni")
 import("//build_extra/deno.gni")
 import("//build_extra/rust/rust.gni")
 
@@ -10,8 +11,8 @@ group("all") {
   deps = [
     ":deno",
     ":deno_ns",
-    ":handlers_test",
     ":test_cc",
+    ":test_rs",
   ]
 }
 
@@ -33,12 +34,29 @@ config("deno_config") {
   }
 }
 
+main_extern = [
+  "$rust_build:libc",
+  "$rust_build:log",
+  "$rust_build:url",
+  "//build_extra/flatbuffers/rust:flatbuffers",
+  ":msg_rs",
+
+  # Indirect rust depdendencies also need to be listed here:
+  # * Linking to `:handlers` or `:libdeno` isn't possible, because they
+  #   already contain some symbols exported by `handlers.rs`. These duplicate
+  #   symbols trip up the linker.
+  # * The `rust_test` and `rust_executable` templates only produce an object
+  #   file, and then invoke an external linker. Transitive rust depencenies
+  #   are not resolved in either step.
+  "$rust_build:idna",
+  "$rust_build:percent_encoding",
+  "$rust_build:unicode_bidi",
+  "$rust_build:unicode_normalization",
+]
+
 rust_executable("deno") {
   source_root = "src/main.rs"
-  extern = [
-    "$rust_build:libc",
-    "$rust_build:log",
-  ]
+  extern = main_extern
   deps = [
     ":libdeno",
   ]
@@ -50,43 +68,15 @@ rust_executable("deno") {
 # ns = no snapshot
 rust_executable("deno_ns") {
   source_root = "src/main.rs"
-  extern = [
-    "$rust_build:libc",
-    "$rust_build:log",
-  ]
+  extern = main_extern
   deps = [
     ":libdeno_nosnapshot",
   ]
 }
 
-rust_staticlib("handlers") {
-  source_root = "src/handlers.rs"
-  extern = [
-    "$rust_build:libc",
-    "$rust_build:url",
-    "$rust_build:log",
-  ]
-}
-
-rust_test("handlers_test") {
-  source_root = "src/handlers.rs"
-  extern = [
-    "$rust_build:libc",
-    "$rust_build:url",
-    "$rust_build:log",
-
-    # Indirect rust depdendencies also need to be listed here:
-    # * Linking to `:handlers` or `:libdeno` isn't possible, because they
-    #   already contain some symbols exported by `handlers.rs`. These duplicate
-    #   symbols trip up the linker.
-    # * The `rust_test` and `rust_executable` templates only produce an object
-    #   file, and then invoke an external linker. Transitive rust depencenies
-    #   are not resolved in either step.
-    "$rust_build:idna",
-    "$rust_build:percent_encoding",
-    "$rust_build:unicode_bidi",
-    "$rust_build:unicode_normalization",
-  ]
+rust_test("test_rs") {
+  source_root = "src/main.rs"
+  extern = main_extern
   deps = [
     ":deno_bindings",
   ]
@@ -100,8 +90,7 @@ executable("test_cc") {
   ]
   deps = [
     ":deno_base_test",
-    ":deno_bindings",
-    ":handlers",
+    ":deno_flatbuffer_builder",
     "//testing/gtest:gtest",
   ]
   configs += [ ":deno_config" ]
@@ -115,7 +104,6 @@ static_library("libdeno") {
   deps = [
     ":create_snapshot_deno",
     ":deno_bindings",
-    ":handlers",
   ]
   configs += [ ":deno_config" ]
 }
@@ -154,20 +142,30 @@ v8_source_set("deno_base_test") {
   configs = [ ":deno_config" ]
 }
 
-v8_source_set("deno_bindings") {
+v8_source_set("deno_flatbuffer_builder") {
   sources = [
     "src/flatbuffer_builder.cc",
     "src/flatbuffer_builder.h",
+  ]
+  deps = [
+    ":deno_base",
+  ]
+  public_deps = [
+    "build_extra/flatbuffers:flatbuffers",
+  ]
+  configs = [ ":deno_config" ]
+}
+
+v8_source_set("deno_bindings") {
+  sources = [
     "src/reply.cc",
     "src/reply.h",
   ]
   deps = [
     ":deno_base",
+    ":deno_flatbuffer_builder",
     ":msg_cpp",
   ]
-  public_deps = [
-    "build_extra/flatbuffers:flatbuffers",
-  ]
   configs = [ ":deno_config" ]
 }
 
@@ -232,7 +230,6 @@ source_set("libdeno_nosnapshot") {
   deps = [
     ":bundle",
     ":deno_bindings",
-    ":handlers",
   ]
   configs += [ ":deno_config" ]
   bundle_outputs = get_target_outputs(":bundle")
@@ -274,6 +271,12 @@ ts_flatbuffer("msg_ts") {
   ]
 }
 
+rust_flatbuffer("msg_rs") {
+  sources = [
+    "src/msg.fbs",
+  ]
+}
+
 # Generates $target_gen_dir/snapshot_deno.cc
 create_snapshot("deno") {
   js = "$target_gen_dir/bundle/main.js"
diff --git a/build_extra/flatbuffers/rust/BUILD.gn b/build_extra/flatbuffers/rust/BUILD.gn
new file mode 100644
index 0000000000..25ba496eee
--- /dev/null
+++ b/build_extra/flatbuffers/rust/BUILD.gn
@@ -0,0 +1,5 @@
+import("//build_extra/rust/rust.gni")
+
+rust_component("flatbuffers") {
+  source_root = "//third_party/flatbuffers/rust/flatbuffers/src/lib.rs"
+}
diff --git a/build_extra/flatbuffers/rust/rust_flatbuffer.gni b/build_extra/flatbuffers/rust/rust_flatbuffer.gni
new file mode 100644
index 0000000000..f5280a8d3a
--- /dev/null
+++ b/build_extra/flatbuffers/rust/rust_flatbuffer.gni
@@ -0,0 +1,44 @@
+import("//build_extra/rust/rust.gni")
+
+# TODO(ry) "flatbuffer.gni" should be "flatbuffers.gni" we should be consistant
+# in our pluralization.
+import("//build_extra/flatbuffers/flatbuffer.gni")
+
+template("rust_flatbuffer") {
+  action_name = "${target_name}_gen"
+  source_set_name = target_name
+  compiled_action_foreach(action_name) {
+    tool = "$flatbuffers_build_location:flatc"
+
+    sources = invoker.sources
+    deps = []
+    out_dir = target_gen_dir
+
+    outputs = [
+      "$out_dir/{{source_name_part}}_generated.rs",
+    ]
+
+    args = [
+      "--rust",
+      "-o",
+      rebase_path(out_dir, root_build_dir),
+      "-I",
+      rebase_path("//", root_build_dir),
+    ]
+    args += [ "{{source}}" ]
+
+    # The deps may have steps that have to run before running flatc.
+    if (defined(invoker.deps)) {
+      deps += invoker.deps
+    }
+  }
+
+  rust_component(source_set_name) {
+    sources = get_target_outputs(":$action_name")
+    source_root = sources[0]
+    deps = [
+      ":$action_name",
+    ]
+    extern = [ "//build_extra/flatbuffers/rust:flatbuffers" ]
+  }
+}
diff --git a/build_extra/rust/rust.gni b/build_extra/rust/rust.gni
index 2fc8228376..f783126ed6 100644
--- a/build_extra/rust/rust.gni
+++ b/build_extra/rust/rust.gni
@@ -163,6 +163,7 @@ template("rust_component") {
                              "is_test",
                              "testonly",
                              "args",
+                             "deps",
                            ])
     if (!defined(invoker.crate_type)) {
       crate_type = "rlib"
diff --git a/js/main.ts b/js/main.ts
index 818e6aa126..7c6fc7dc57 100644
--- a/js/main.ts
+++ b/js/main.ts
@@ -16,10 +16,11 @@ function assignCmdId(): number {
 
 function startMsg(cmdId: number): Uint8Array {
   const builder = new flatbuffers.Builder();
-  const msg = fbs.Start.createStart(builder, 0);
+  fbs.Start.startStart(builder);
+  const startOffset = fbs.Start.endStart(builder);
   fbs.Base.startBase(builder);
   fbs.Base.addCmdId(builder, cmdId);
-  fbs.Base.addMsg(builder, msg);
+  fbs.Base.addMsg(builder, startOffset);
   fbs.Base.addMsgType(builder, fbs.Any.Start);
   builder.finish(fbs.Base.endBase(builder));
   return builder.asUint8Array();
diff --git a/js/msg_generated.ts b/js/msg_generated.ts
index af40bf1484..83d75490f2 100644
--- a/js/msg_generated.ts
+++ b/js/msg_generated.ts
@@ -197,11 +197,21 @@ __init(i:number, bb:flatbuffers.ByteBuffer):Start {
   return this;
 };
 
+/**
+ * @param {flatbuffers.ByteBuffer} bb
+ * @param {Start=} obj
+ * @returns {Start}
+ */
+static getRootAsStart(bb:flatbuffers.ByteBuffer, obj?:Start):Start {
+  return (obj || new Start).__init(bb.readInt32(bb.position()) + bb.position(), bb);
+};
+
 /**
  * @returns {number}
  */
 unused():number {
-  return this.bb!.readInt8(this.bb_pos);
+  var offset = this.bb!.__offset(this.bb_pos, 4);
+  return offset ? this.bb!.readInt8(this.bb_pos + offset) : 0;
 };
 
 /**
@@ -209,7 +219,7 @@ unused():number {
  * @returns {boolean}
  */
 mutate_unused(value:number):boolean {
-  var offset = this.bb!.__offset(this.bb_pos, 0);
+  var offset = this.bb!.__offset(this.bb_pos, 4);
 
   if (offset === 0) {
     return false;
@@ -219,15 +229,28 @@ mutate_unused(value:number):boolean {
   return true;
 };
 
+/**
+ * @param {flatbuffers.Builder} builder
+ */
+static startStart(builder:flatbuffers.Builder) {
+  builder.startObject(1);
+};
+
 /**
  * @param {flatbuffers.Builder} builder
  * @param {number} unused
+ */
+static addUnused(builder:flatbuffers.Builder, unused:number) {
+  builder.addFieldInt8(0, unused, 0);
+};
+
+/**
+ * @param {flatbuffers.Builder} builder
  * @returns {flatbuffers.Offset}
  */
-static createStart(builder:flatbuffers.Builder, unused: number):flatbuffers.Offset {
-  builder.prep(1, 1);
-  builder.writeInt8(unused);
-  return builder.offset();
+static endStart(builder:flatbuffers.Builder):flatbuffers.Offset {
+  var offset = builder.endObject();
+  return offset;
 };
 
 }
@@ -735,11 +758,21 @@ __init(i:number, bb:flatbuffers.ByteBuffer):Exit {
   return this;
 };
 
+/**
+ * @param {flatbuffers.ByteBuffer} bb
+ * @param {Exit=} obj
+ * @returns {Exit}
+ */
+static getRootAsExit(bb:flatbuffers.ByteBuffer, obj?:Exit):Exit {
+  return (obj || new Exit).__init(bb.readInt32(bb.position()) + bb.position(), bb);
+};
+
 /**
  * @returns {number}
  */
 code():number {
-  return this.bb!.readInt32(this.bb_pos);
+  var offset = this.bb!.__offset(this.bb_pos, 4);
+  return offset ? this.bb!.readInt32(this.bb_pos + offset) : 0;
 };
 
 /**
@@ -747,7 +780,7 @@ code():number {
  * @returns {boolean}
  */
 mutate_code(value:number):boolean {
-  var offset = this.bb!.__offset(this.bb_pos, 0);
+  var offset = this.bb!.__offset(this.bb_pos, 4);
 
   if (offset === 0) {
     return false;
@@ -757,15 +790,28 @@ mutate_code(value:number):boolean {
   return true;
 };
 
+/**
+ * @param {flatbuffers.Builder} builder
+ */
+static startExit(builder:flatbuffers.Builder) {
+  builder.startObject(1);
+};
+
 /**
  * @param {flatbuffers.Builder} builder
  * @param {number} code
+ */
+static addCode(builder:flatbuffers.Builder, code:number) {
+  builder.addFieldInt32(0, code, 0);
+};
+
+/**
+ * @param {flatbuffers.Builder} builder
  * @returns {flatbuffers.Offset}
  */
-static createExit(builder:flatbuffers.Builder, code: number):flatbuffers.Offset {
-  builder.prep(4, 4);
-  builder.writeInt32(code);
-  return builder.offset();
+static endExit(builder:flatbuffers.Builder):flatbuffers.Offset {
+  var offset = builder.endObject();
+  return offset;
 };
 
 }
@@ -795,11 +841,21 @@ __init(i:number, bb:flatbuffers.ByteBuffer):TimerStart {
   return this;
 };
 
+/**
+ * @param {flatbuffers.ByteBuffer} bb
+ * @param {TimerStart=} obj
+ * @returns {TimerStart}
+ */
+static getRootAsTimerStart(bb:flatbuffers.ByteBuffer, obj?:TimerStart):TimerStart {
+  return (obj || new TimerStart).__init(bb.readInt32(bb.position()) + bb.position(), bb);
+};
+
 /**
  * @returns {number}
  */
 id():number {
-  return this.bb!.readUint32(this.bb_pos);
+  var offset = this.bb!.__offset(this.bb_pos, 4);
+  return offset ? this.bb!.readUint32(this.bb_pos + offset) : 0;
 };
 
 /**
@@ -807,7 +863,7 @@ id():number {
  * @returns {boolean}
  */
 mutate_id(value:number):boolean {
-  var offset = this.bb!.__offset(this.bb_pos, 0);
+  var offset = this.bb!.__offset(this.bb_pos, 4);
 
   if (offset === 0) {
     return false;
@@ -821,7 +877,8 @@ mutate_id(value:number):boolean {
  * @returns {boolean}
  */
 interval():boolean {
-  return !!this.bb!.readInt8(this.bb_pos + 4);
+  var offset = this.bb!.__offset(this.bb_pos, 6);
+  return offset ? !!this.bb!.readInt8(this.bb_pos + offset) : false;
 };
 
 /**
@@ -829,7 +886,7 @@ interval():boolean {
  * @returns {boolean}
  */
 mutate_interval(value:boolean):boolean {
-  var offset = this.bb!.__offset(this.bb_pos, 4);
+  var offset = this.bb!.__offset(this.bb_pos, 6);
 
   if (offset === 0) {
     return false;
@@ -843,7 +900,8 @@ mutate_interval(value:boolean):boolean {
  * @returns {number}
  */
 delay():number {
-  return this.bb!.readInt32(this.bb_pos + 8);
+  var offset = this.bb!.__offset(this.bb_pos, 8);
+  return offset ? this.bb!.readInt32(this.bb_pos + offset) : 0;
 };
 
 /**
@@ -861,20 +919,44 @@ mutate_delay(value:number):boolean {
   return true;
 };
 
+/**
+ * @param {flatbuffers.Builder} builder
+ */
+static startTimerStart(builder:flatbuffers.Builder) {
+  builder.startObject(3);
+};
+
 /**
  * @param {flatbuffers.Builder} builder
  * @param {number} id
+ */
+static addId(builder:flatbuffers.Builder, id:number) {
+  builder.addFieldInt32(0, id, 0);
+};
+
+/**
+ * @param {flatbuffers.Builder} builder
  * @param {boolean} interval
+ */
+static addInterval(builder:flatbuffers.Builder, interval:boolean) {
+  builder.addFieldInt8(1, +interval, +false);
+};
+
+/**
+ * @param {flatbuffers.Builder} builder
  * @param {number} delay
+ */
+static addDelay(builder:flatbuffers.Builder, delay:number) {
+  builder.addFieldInt32(2, delay, 0);
+};
+
+/**
+ * @param {flatbuffers.Builder} builder
  * @returns {flatbuffers.Offset}
  */
-static createTimerStart(builder:flatbuffers.Builder, id: number, interval: boolean, delay: number):flatbuffers.Offset {
-  builder.prep(4, 12);
-  builder.writeInt32(delay);
-  builder.pad(3);
-  builder.writeInt8(+interval);
-  builder.writeInt32(id);
-  return builder.offset();
+static endTimerStart(builder:flatbuffers.Builder):flatbuffers.Offset {
+  var offset = builder.endObject();
+  return offset;
 };
 
 }
@@ -904,11 +986,21 @@ __init(i:number, bb:flatbuffers.ByteBuffer):TimerReady {
   return this;
 };
 
+/**
+ * @param {flatbuffers.ByteBuffer} bb
+ * @param {TimerReady=} obj
+ * @returns {TimerReady}
+ */
+static getRootAsTimerReady(bb:flatbuffers.ByteBuffer, obj?:TimerReady):TimerReady {
+  return (obj || new TimerReady).__init(bb.readInt32(bb.position()) + bb.position(), bb);
+};
+
 /**
  * @returns {number}
  */
 id():number {
-  return this.bb!.readUint32(this.bb_pos);
+  var offset = this.bb!.__offset(this.bb_pos, 4);
+  return offset ? this.bb!.readUint32(this.bb_pos + offset) : 0;
 };
 
 /**
@@ -916,7 +1008,7 @@ id():number {
  * @returns {boolean}
  */
 mutate_id(value:number):boolean {
-  var offset = this.bb!.__offset(this.bb_pos, 0);
+  var offset = this.bb!.__offset(this.bb_pos, 4);
 
   if (offset === 0) {
     return false;
@@ -930,7 +1022,8 @@ mutate_id(value:number):boolean {
  * @returns {boolean}
  */
 done():boolean {
-  return !!this.bb!.readInt8(this.bb_pos + 4);
+  var offset = this.bb!.__offset(this.bb_pos, 6);
+  return offset ? !!this.bb!.readInt8(this.bb_pos + offset) : false;
 };
 
 /**
@@ -938,7 +1031,7 @@ done():boolean {
  * @returns {boolean}
  */
 mutate_done(value:boolean):boolean {
-  var offset = this.bb!.__offset(this.bb_pos, 4);
+  var offset = this.bb!.__offset(this.bb_pos, 6);
 
   if (offset === 0) {
     return false;
@@ -948,18 +1041,36 @@ mutate_done(value:boolean):boolean {
   return true;
 };
 
+/**
+ * @param {flatbuffers.Builder} builder
+ */
+static startTimerReady(builder:flatbuffers.Builder) {
+  builder.startObject(2);
+};
+
 /**
  * @param {flatbuffers.Builder} builder
  * @param {number} id
+ */
+static addId(builder:flatbuffers.Builder, id:number) {
+  builder.addFieldInt32(0, id, 0);
+};
+
+/**
+ * @param {flatbuffers.Builder} builder
  * @param {boolean} done
+ */
+static addDone(builder:flatbuffers.Builder, done:boolean) {
+  builder.addFieldInt8(1, +done, +false);
+};
+
+/**
+ * @param {flatbuffers.Builder} builder
  * @returns {flatbuffers.Offset}
  */
-static createTimerReady(builder:flatbuffers.Builder, id: number, done: boolean):flatbuffers.Offset {
-  builder.prep(4, 8);
-  builder.pad(3);
-  builder.writeInt8(+done);
-  builder.writeInt32(id);
-  return builder.offset();
+static endTimerReady(builder:flatbuffers.Builder):flatbuffers.Offset {
+  var offset = builder.endObject();
+  return offset;
 };
 
 }
@@ -989,11 +1100,21 @@ __init(i:number, bb:flatbuffers.ByteBuffer):TimerClear {
   return this;
 };
 
+/**
+ * @param {flatbuffers.ByteBuffer} bb
+ * @param {TimerClear=} obj
+ * @returns {TimerClear}
+ */
+static getRootAsTimerClear(bb:flatbuffers.ByteBuffer, obj?:TimerClear):TimerClear {
+  return (obj || new TimerClear).__init(bb.readInt32(bb.position()) + bb.position(), bb);
+};
+
 /**
  * @returns {number}
  */
 id():number {
-  return this.bb!.readUint32(this.bb_pos);
+  var offset = this.bb!.__offset(this.bb_pos, 4);
+  return offset ? this.bb!.readUint32(this.bb_pos + offset) : 0;
 };
 
 /**
@@ -1001,7 +1122,7 @@ id():number {
  * @returns {boolean}
  */
 mutate_id(value:number):boolean {
-  var offset = this.bb!.__offset(this.bb_pos, 0);
+  var offset = this.bb!.__offset(this.bb_pos, 4);
 
   if (offset === 0) {
     return false;
@@ -1011,15 +1132,28 @@ mutate_id(value:number):boolean {
   return true;
 };
 
+/**
+ * @param {flatbuffers.Builder} builder
+ */
+static startTimerClear(builder:flatbuffers.Builder) {
+  builder.startObject(1);
+};
+
 /**
  * @param {flatbuffers.Builder} builder
  * @param {number} id
+ */
+static addId(builder:flatbuffers.Builder, id:number) {
+  builder.addFieldInt32(0, id, 0);
+};
+
+/**
+ * @param {flatbuffers.Builder} builder
  * @returns {flatbuffers.Offset}
  */
-static createTimerClear(builder:flatbuffers.Builder, id: number):flatbuffers.Offset {
-  builder.prep(4, 4);
-  builder.writeInt32(id);
-  return builder.offset();
+static endTimerClear(builder:flatbuffers.Builder):flatbuffers.Offset {
+  var offset = builder.endObject();
+  return offset;
 };
 
 }
diff --git a/src/binding.rs b/src/binding.rs
index 72e8af996b..1ef376dff1 100644
--- a/src/binding.rs
+++ b/src/binding.rs
@@ -1,11 +1,9 @@
 // Copyright 2018 the Deno authors. All rights reserved. MIT license.
 #![allow(dead_code)]
-
 extern crate libc;
 use libc::c_char;
 use libc::c_int;
 use libc::c_void;
-use libc::uint32_t;
 
 #[repr(C)]
 pub struct DenoC {
@@ -14,10 +12,10 @@ pub struct DenoC {
 
 #[repr(C)]
 pub struct deno_buf {
-  alloc_ptr: *mut u8,
-  alloc_len: usize,
-  data_ptr: *mut u8,
-  data_len: usize,
+  pub alloc_ptr: *mut u8,
+  pub alloc_len: usize,
+  pub data_ptr: *mut u8,
+  pub data_len: usize,
 }
 
 type DenoRecvCb = unsafe extern "C" fn(d: *const DenoC, buf: deno_buf);
@@ -36,18 +34,4 @@ extern "C" {
     js_source: *const c_char,
   ) -> c_int;
   pub fn deno_handle_msg_from_js(d: *const DenoC, buf: deno_buf);
-  pub fn deno_reply_error(
-    d: *const DenoC,
-    cmd_id: uint32_t,
-    msg: *const c_char,
-  );
-  pub fn deno_reply_null(d: *const DenoC, cmd_id: uint32_t);
-  pub fn deno_reply_code_fetch(
-    d: *const DenoC,
-    cmd_id: uint32_t,
-    module_name: *const c_char,
-    filename: *const c_char,
-    source_code: *const c_char,
-    output_code: *const c_char,
-  );
 }
diff --git a/src/handlers.rs b/src/handlers.rs
index e8e197e60c..0f6ed094d4 100644
--- a/src/handlers.rs
+++ b/src/handlers.rs
@@ -1,20 +1,16 @@
 // Copyright 2018 the Deno authors. All rights reserved. MIT license.
-extern crate libc;
-#[macro_use]
-extern crate log;
-extern crate url;
-
+use binding::{deno_buf, deno_set_response, DenoC};
+use flatbuffers;
 use libc::c_char;
+use libc::uint32_t;
+use msg_generated::deno as msg;
 use std::ffi::CStr;
-use std::ffi::CString;
 use std::fs::File;
 use std::io::Read;
 use std::path::Path;
+use url;
 use url::Url;
 
-mod binding;
-use binding::{deno_reply_code_fetch, deno_reply_error, DenoC};
-
 // TODO(ry) SRC_DIR is just a placeholder for future caching functionality.
 static SRC_DIR: &str = "/Users/rld/.deno/src/";
 const ASSET_PREFIX: &str = "/$asset$/";
@@ -30,9 +26,14 @@ fn string_from_ptr(ptr: *const c_char) -> String {
   String::from(cstr.to_str().unwrap())
 }
 
-fn as_cstring(s: &String) -> CString {
-  CString::new(s.as_str()).unwrap()
+/*
+// reply_start partially implemented here https://gist.github.com/ry/297c83e0ac8722c045db1b097cdb6afc
+pub fn deno_handle_msg_from_js(d: *const DenoC, buf: deno_buf) {
+    let s = std::slice::from_raw_parts(buf.data_ptr, buf.data_len);
+    buf.data_ptr
+    get_root()
 }
+*/
 
 // Prototype: https://github.com/ry/deno/blob/golang/os.go#L56-L68
 #[allow(dead_code)]
@@ -183,6 +184,68 @@ fn test_resolve_module() {
   }
 }
 
+pub fn reply_code_fetch(
+  d: *const DenoC,
+  cmd_id: uint32_t,
+  module_name: &String,
+  filename: &String,
+  source_code: &String,
+  output_code: &String,
+) {
+  let mut builder = flatbuffers::FlatBufferBuilder::new();
+  let msg_args = msg::CodeFetchResArgs {
+    module_name: builder.create_string(module_name),
+    filename: builder.create_string(filename),
+    source_code: builder.create_string(source_code),
+    output_code: builder.create_string(output_code),
+    ..Default::default()
+  };
+  let msg = msg::CreateCodeFetchRes(&mut builder, &msg_args);
+  builder.finish(msg);
+  let args = msg::BaseArgs {
+    cmdId: cmd_id,
+    msg: Some(msg.union()),
+    msg_type: msg::Any::CodeFetchRes,
+    ..Default::default()
+  };
+  set_response_base(d, &mut builder, &args)
+}
+
+fn reply_error(d: *const DenoC, cmd_id: u32, msg: &String) {
+  let mut builder = flatbuffers::FlatBufferBuilder::new();
+  // println!("reply_error{}", msg);
+  let args = msg::BaseArgs {
+    cmdId: cmd_id,
+    error: builder.create_string(msg),
+    ..Default::default()
+  };
+  set_response_base(d, &mut builder, &args)
+}
+
+fn set_response_base(
+  d: *const DenoC,
+  builder: &mut flatbuffers::FlatBufferBuilder,
+  args: &msg::BaseArgs,
+) {
+  let base = msg::CreateBase(builder, &args);
+  builder.finish(base);
+  let data = builder.get_active_buf_slice();
+  // println!("buf slice {} {} {} {} {}", data[0], data[1], data[2], data[3], data[4]);
+  let buf = deno_buf {
+    // TODO(ry)
+    // The deno_buf / ImportBuf / ExportBuf semantics should be such that we do not need to yield
+    // ownership. Temporarally there is a hack in ImportBuf that when alloc_ptr is null, it will
+    // memcpy the deno_buf into V8 instead of doing zero copy.
+    alloc_ptr: 0 as *mut u8,
+    alloc_len: 0,
+    data_ptr: data.as_ptr() as *mut u8,
+    data_len: data.len(),
+  };
+  // println!("data_ptr {:p}", data_ptr);
+  // println!("data_len {}", data.len());
+  unsafe { deno_set_response(d, buf) }
+}
+
 // https://github.com/ry/deno/blob/golang/os.go#L100-L154
 #[no_mangle]
 pub extern "C" fn handle_code_fetch(
@@ -198,8 +261,7 @@ pub extern "C" fn handle_code_fetch(
   if result.is_err() {
     let err = result.unwrap_err();
     let errmsg = format!("{} {} {}", err, module_specifier, containing_file);
-    let errmsg_c = as_cstring(&errmsg);
-    unsafe { deno_reply_error(d, cmd_id, errmsg_c.as_ptr()) };
+    reply_error(d, cmd_id, &errmsg);
     return;
   }
   let (module_name, filename) = result.unwrap();
@@ -224,8 +286,7 @@ pub extern "C" fn handle_code_fetch(
     if result.is_err() {
       let err = result.unwrap_err();
       let errmsg = format!("{} {}", err, filename);
-      let errmsg_c = as_cstring(&errmsg);
-      unsafe { deno_reply_error(d, cmd_id, errmsg_c.as_ptr()) };
+      reply_error(d, cmd_id, &errmsg);
       return;
     }
     let mut f = result.unwrap();
@@ -233,24 +294,21 @@ pub extern "C" fn handle_code_fetch(
     if result.is_err() {
       let err = result.unwrap_err();
       let errmsg = format!("{} {}", err, filename);
-      let errmsg_c = as_cstring(&errmsg);
-      unsafe { deno_reply_error(d, cmd_id, errmsg_c.as_ptr()) };
+      reply_error(d, cmd_id, &errmsg);
       return;
     }
   }
 
   let output_code = String::new(); //load_output_code_cache(filename, source_code);
 
-  unsafe {
-    deno_reply_code_fetch(
-      d,
-      cmd_id,
-      as_cstring(&module_name).as_ptr(),
-      as_cstring(&filename).as_ptr(),
-      as_cstring(&source_code).as_ptr(),
-      as_cstring(&output_code).as_ptr(),
-    )
-  }
+  reply_code_fetch(
+    d,
+    cmd_id,
+    &module_name,
+    &filename,
+    &source_code,
+    &output_code,
+  )
 }
 
 fn is_remote(_module_name: &String) -> bool {
diff --git a/src/main.rs b/src/main.rs
index 2b0a72c917..f9f0172b6e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,12 +1,17 @@
 extern crate libc;
 #[macro_use]
 extern crate log;
+extern crate flatbuffers;
+extern crate msg_rs as msg_generated;
+extern crate url;
 
 use libc::c_int;
 use std::ffi::CStr;
 use std::ffi::CString;
 use std::ptr;
 
+mod handlers;
+pub use handlers::*;
 mod binding;
 use binding::{
   deno_delete, deno_execute, deno_handle_msg_from_js, deno_init,
diff --git a/src/msg.fbs b/src/msg.fbs
index b07da99cf4..cb1cf57a91 100644
--- a/src/msg.fbs
+++ b/src/msg.fbs
@@ -23,7 +23,7 @@ table Base {
   msg: Any;
 }
 
-struct Start {
+table Start {
   unused: int8;
 }
 
@@ -54,22 +54,22 @@ table CodeCache {
   output_code: string;
 }
 
-struct Exit {
+table Exit {
   code: int;
 }
 
-struct TimerStart {
+table TimerStart {
   id: uint;
   interval: bool;
   delay: int;
 }
 
-struct TimerReady {
+table TimerReady {
   id: uint;
   done: bool;
 }
 
-struct TimerClear {
+table TimerClear {
   id: uint;
 }
 
diff --git a/src/reply.cc b/src/reply.cc
index ffb0d493a0..435f76f74c 100644
--- a/src/reply.cc
+++ b/src/reply.cc
@@ -21,35 +21,6 @@
 
 extern "C" {
 
-void deno_reply_error(Deno* d, uint32_t cmd_id, const char* error_msg) {
-  // printf("deno_reply_error: %s\n", error_msg);
-  deno::FlatBufferBuilder builder;
-  auto error_msg_ = error_msg ? builder.CreateString(error_msg) : 0;
-  auto base = deno::CreateBase(builder, cmd_id, error_msg_);
-  builder.Finish(base);
-  deno_set_response(d, builder.ExportBuf());
-}
-
-void deno_reply_null(Deno* d, uint32_t cmd_id) {
-  deno_reply_error(d, cmd_id, nullptr);
-}
-
-void deno_reply_code_fetch(Deno* d, uint32_t cmd_id, const char* module_name,
-                           const char* filename, const char* source_code,
-                           const char* output_code) {
-  deno::FlatBufferBuilder builder;
-  auto module_name_ = builder.CreateString(module_name);
-  auto filename_ = builder.CreateString(filename);
-  auto source_code_ = builder.CreateString(source_code);
-  auto output_code_ = builder.CreateString(output_code);
-  auto code_fetch_res = deno::CreateCodeFetchRes(
-      builder, module_name_, filename_, source_code_, output_code_);
-  auto base = deno::CreateBase(builder, cmd_id, 0, deno::Any_CodeFetchRes,
-                               code_fetch_res.Union());
-  builder.Finish(base);
-  deno_set_response(d, builder.ExportBuf());
-}
-
 void deno_reply_start(Deno* d, uint32_t cmd_id, int argc, char* argv[],
                       char* cwd) {
   deno::FlatBufferBuilder builder;
diff --git a/src/reply.h b/src/reply.h
index 4b16204da3..8815abd52d 100644
--- a/src/reply.h
+++ b/src/reply.h
@@ -12,16 +12,6 @@
 #include "deno.h"
 
 extern "C" {
-
-void deno_reply_null(Deno* d, uint32_t cmd_id);
-void deno_reply_error(Deno* d, uint32_t cmd_id, const char* error_msg);
-
-void deno_reply_start(Deno* d, uint32_t cmd_id, int argc, char* argv[],
-                      char* cwd);
-void deno_reply_code_fetch(Deno* d, uint32_t cmd_id, const char* module_name,
-                           const char* filename, const char* source_code,
-                           const char* output_code);
-
 // Parse incoming messages with C++ Flatbuffers, call into rust handlers.
 void deno_handle_msg_from_js(Deno* d, deno_buf buf);
 }
diff --git a/tools/test.py b/tools/test.py
index e62efd0f6b..3edfa4e015 100755
--- a/tools/test.py
+++ b/tools/test.py
@@ -24,9 +24,9 @@ def main(argv):
     check_exists(test_cc)
     run([test_cc])
 
-    handlers_test = os.path.join(build_dir, "handlers_test" + executable_suffix)
-    check_exists(handlers_test)
-    run([handlers_test])
+    test_rs = os.path.join(build_dir, "test_rs" + executable_suffix)
+    check_exists(test_rs)
+    run([test_rs])
 
     deno_exe = os.path.join(build_dir, "deno" + executable_suffix)
     check_exists(deno_exe)