I remembered one more think.
Remote net.box convents nils to box.NULLs but your approach with {...} ignores it.
Please, change pairs({...}) to select(). Also it's interesting to see following cases: uuid and decimal (but only for 2.3+)
Notice that net.box:call can't send and receive functions.

`function() return uuid() end` returns an error  in this implementation:
```
- error: '[string "return require(''uuid'')():__serialize()"]:1: ''struct tt_uuid''
     has no member named ''__serialize'''
```

But remote net.box returns:
```
- error: unsupported Lua type 'cdata'

``` Also please see  https://github.com/tarantool/tarantool/issues/4602

It seems that correct way is to use msgpack.decode(msgpack.encode()), but it will lead to performance degradation
so the problem should be discussed more closely.

>Четверг,  7 ноября 2019, 17:27 +03:00 от Maria Khaydich <maria.khaydich@tarantool.org>:
>
>Thank you for the comment!
>I’ve checked the behavior and previous version does not indeed cover the case with box.NULL. Suitable fix and tests were added. 
> 
>>Четверг, 7 ноября 2019, 17:08 +03:00 от Бабин Олег < olegrok@tarantool.org >:
>> 
>>Maria, thanks for your patch!
>>
>>But as I see you don't consider the case of box.NULL that has 'cdata' type, but doesn't have
>>__serialize metamethod.
>>
>>It will lead to an error:
>>```
>>- error: '[string "return x:__serialize()"]:1: ''void *'' has no member named ''__serialize'''
>>...
>>```
>>>Четверг, 7 ноября 2019, 16:47 +03:00 от Maria < maria.khaydich@tarantool.org >:
>>>
>>>+ if type(res) == 'cdata' then
>>>+ results[n] = res:__serialize()
>>>+ end
>>
>>-- 
>>Oleg Babin
> 
> 
>--
>Maria Khaydich
> 
-- 
Oleg Babin