diff --git a/lib/futu.ex b/lib/futu.ex
index 7a135d8..fe9cb6e 100644
--- a/lib/futu.ex
+++ b/lib/futu.ex
@@ -131,10 +131,11 @@ defmodule Futu do
     rescue
       e in MatchError ->
         case e do
-          %{message: "TCP timeout"} ->
-            request(pid, module, opts)
+          # %{message: "TCP timeout"} ->
+          #   request(pid, module, opts)
 
           %{term: {:error, "Message size exceed"}} ->
+            Logger.warn("Message size exceed")
             GenServer.stop(pid)
             {:error, "Message size exceed, proto_id: #{module.proto_id}"}
 
@@ -151,7 +152,7 @@ defmodule Futu do
     end
   end
 
-  defp wait_until_free(pid) do
+  def wait_until_free(pid) do
     case GenServer.call(pid, :is_occupied) do
       true ->
         :timer.sleep(100)
diff --git a/lib/futu/gen_server/heartbeat.ex b/lib/futu/gen_server/heartbeat.ex
index 5cf47d8..6a5b656 100644
--- a/lib/futu/gen_server/heartbeat.ex
+++ b/lib/futu/gen_server/heartbeat.ex
@@ -21,6 +21,7 @@ defmodule Futu.GenServer.HeartBeat do
 
   def handle_info({:heartbeat, tcp_pid, interval}, state) do
     msg = Futu._heartbeat()
+    Futu.wait_until_free(tcp_pid)
     GenServer.cast(tcp_pid, {:send_heartbeat, msg})
     schedule_heartbeat(tcp_pid, interval)
     {:noreply, state}
diff --git a/lib/futu/gen_server/tcp.ex b/lib/futu/gen_server/tcp.ex
index d9a57df..412898d 100644
--- a/lib/futu/gen_server/tcp.ex
+++ b/lib/futu/gen_server/tcp.ex
@@ -27,14 +27,19 @@ defmodule Futu.GenServer.TCP do
     host_charlist = String.to_charlist(host)
 
     {:ok, socket} =
-      :gen_tcp.connect(host_charlist, port, [:binary, active: true, keepalive: true])
+      :gen_tcp.connect(host_charlist, port, [
+        :binary,
+        active: true,
+        keepalive: true,
+        buffer: 1024 * 1024
+      ])
 
     {:ok, %{socket: socket, from: nil, is_occupied: false, msg: "", proto_id: nil}}
   end
 
   def handle_call({:send, msg, proto_id}, from, state) do
     :ok = :gen_tcp.send(state.socket, msg)
-    new_state = %{state | from: from, msg: "", proto_id: proto_id}
+    new_state = %{state | from: from, msg: "", proto_id: proto_id, is_occupied: true}
 
     {:noreply, new_state}
   end
@@ -57,9 +62,11 @@ defmodule Futu.GenServer.TCP do
   end
 
   def handle_info({:tcp, _socket, msg}, state) do
+    print_message(msg)
+
     case Response.get_proto_id(msg) do
       {:ok, 1004} ->
-        {:noreply, state}
+        {:noreply, reset_state(state)}
 
       {:ok, 2218} ->
         {:noreply, state}
@@ -104,7 +111,7 @@ defmodule Futu.GenServer.TCP do
             {:noreply, reset_state(new_state)}
 
           true ->
-            {:noreply, %{new_state | is_occupied: true}}
+            {:noreply, new_state}
         end
     end
   end
@@ -118,4 +125,32 @@ defmodule Futu.GenServer.TCP do
   defp reset_state(state) do
     %{state | msg: "", proto_id: nil, is_occupied: false}
   end
+
+  defp is_message_head?(packet) do
+    case Response.get_proto_id(packet) do
+      {:ok, _proto_id} -> true
+      _ -> false
+    end
+  end
+
+  defp print_message(message) do
+    payload = inspect(:binary.bin_to_list(message), limit: :infinity)
+    Logger.info("is head?: #{inspect(is_message_head?(message))}")
+    Logger.info("message: #{payload}")
+    Logger.info("length: #{byte_size(message)}")
+
+    case Response.get_proto_id(message) do
+      {:ok, proto_id} ->
+        Logger.info("proto_id: #{proto_id}")
+
+        body_size = Response.get_body_size(message)
+        total_msg_size = body_size + Response.header_length()
+        Logger.info("supposed length: #{total_msg_size}")
+
+      _ ->
+        nil
+    end
+
+    Logger.info("-------------------------------------------------")
+  end
 end