[I need help..] two-way communication with LoRa, GPS, Yun.rev2

I'm really trying to make two-way communication system using LoRa.
What client will send to server is GPS data(latitude, longitude)

I'd like to make the system like this.
Dragino LoRa GPS Tracker : 13 Steps (with Pictures) - Instructables

this site says client and server consist of like this as below

  1. Client Side: Arduino + [Lora/GPS Shield] (868Mhz).
  2. Server Side: Arduino + [Lora Shield] (868Mhz) + Yun Shield + USB flash.

I made client side exactly the same as I mentioned above.
But I made server side that consists of [Yun.rev2] + [Lora Shield] (868Mhz)
The reason why I use [Yun.rev2] is ... [Yun.rev2] can be a Arduino as well as Yun shield.

And I connected [Yun.rev2] with my notebook successfully.
I checked server side's port related to [Yun.rev2] which is 서버에 연결되어 있는 포트 이름
and selected 서버보드이름 as server side's board
and 클라이언트에 연결되어 있는 포트이름, 클라이언트보드이름 for client side.

my code for client as below
클라이언트 코드

my code for server as below
서버 코드

but I think there's some error.
We've got this on Serial Monitor

Actually, we want to get this on server's serial monitor
image

I'm having trouble in finding error. Please help novice

@chelwoon_moon, your topic has been moved to a more suitable location on the forum. Introductory Tutorials is for tutorials that e.g. you write, not for questions. Feel free to write a tutorial once you have solved your problem :wink:

Note: we can't see your code

Also note that your post contains stuff that is not in English.