Using terminal screen sharing with Unix Screen

Screen can be used to share a screen between two users-

screen -R screen-test


That opens a screen, now allow multiuser access in the screen session via the command CTRL-A :multiuser on (all 'screen' commands start with the screen escape sequence, CTRL-A).

CTRL-A
:multiuser on


Next, the host must grant permission to the remote user to access the screen session using the command CTRL-A :acladd user_name where user_name is the remote user's login ID.

CTRL-A
:acladd username


The remote user can now connect to the hosts 'screen' session. The syntax to connect to another user's screen session is screen -x host_username/sessionname.

screen -x username/screen-test


Thanks to Ubuntu Community.