g++: error: unrecognized '-std=c++17' (what is g++ version and how to install)

I am working on RHEL 7.5 and trying to compile a uWebSocket (This exaple) code. I clone the project and open it. When I start make on Makefile I got this error;

BroadcastingEchoServer uSockets/*.o -lz;
g++: error: unrecognized command line option '-std=c++17'
make: [examples] Error 1>

The main problem is -std=c++17 is not recognized. How can I control what c++ version I have (that 17 in the end) and how can I install required version.

gcc --version

gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-39)
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Thanks