First type the command:
ps -aux | grep redis
which will list the job(s) currently running on your server. In my case, I have
redis 628 0.1 0.0 29348 592 ? Ssl Oct25 23:15 /usr/bin/redis-server 127.0.0.1:6379
Second kill the job, in my case it has the number 628, so type:
sudo kill -9 628
Third, restart the redis service:
sudo service redis-server restart