WebSocket++ Makefile.txt error - Linux

最近因為研究網路websocket 下載github上的專案 websocketpp
https://github.com/zaphoyd/websocketpp
欲測試裡面examples/echo_server 利用
Makefile.txt 下 cmake . 發生錯誤
目前還在研究Linux系統，以下是錯誤訊息
jay@jay-D830MT:~$ cd websocketpp/examples/echo_server
jay@jay-D830MT:~/websocketpp/examples/echo_server$ ls
CMakeCache.txt CMakeLists.txt echo_server.cpp
CMakeFiles echo_handler.hpp SConscript
jay@jay-D830MT:~/websocketpp/examples/echo_server$ cmake .
CMake Error at CMakeLists.txt:5 (init_target):
Unknown CMake command "init_target".


CMake Warning (dev) in CMakeLists.txt:
No cmake_minimum_required command is present. A line of code such as

cmake_minimum_required(VERSION 3.5)

should be added at the top of the file. The version specified may be lower
if you wish to support older CMake versions for this project. For more
information run "cmake --help-policy CMP0000".
This warning is for project developers. Use -Wno-dev to suppress it.

-- Configuring incomplete, errors occurred!
See also
"/home/jay/websocketpp/examples/echo_server/CMakeFiles/CMakeOutput.log".

根據錯誤內容有log 檔在CMakeOutput.log
CMakeLists.txt:5 (init_target): 這裡頭有問題

請問有人可以幫忙測試看看問題在哪邊嗎？

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