Currently if you want to start your development server at local i.e on port:8000 , but you are unable to start it so,you have start another setup on bench start(working setup) and another on bench serve --port .
Problem is That your system is running one setup unnecessarily and wasting RAM of your system also keep busying database with another setup,some time mysql crashes happens .
Solution:
1.goto path to frappe-bench cd /home/username/workspace/frappe-bench
2. Find PROFILE on current Directory
that file contains following things
redis_cache: redis-server config/redis_cache.conf
redis_socketio: redis-server config/redis_socketio.conf
redis_queue: redis-server config/redis_queue.conf
web: bench serve --port 8000
socketio: /usr/local/bin/node apps/frappe/socketio.js
watch: bench watch
schedule: bench schedule
worker_short: bench worker --queue short --quiet
worker_long: bench worker --queue long --quiet
worker_default: bench worker --queue default --quiet
3.you have to edit this file, by removing all –quiet keyword from this file and save it
4. then go to terminal and enter command lsof -i:8000
5.after that you are able to bench start