Some introductory codes for Yue Wu's summer project at the University of Nottingham

Server commands

Check active screen sessions
```
screen -ls
```
create a new screen
```
screen -S session_name
```
detach the screen session (within the session)
```
ctrl + a + d
```
detach the screen session (from outside the session)
```
screen -XS session_name detach
```
reattach the screen session
```
screen -r session_name
```
kill a screen session
```
screen -X -S session_name quit
```