antony@wakeman:~$ xeyes
debug1: client_input_channel_open: ctype x11 rchan 3 win 65536 max 16384
debug1: client_request_x11: request from 127.0.0.1 3330
debug1: channel 1: new [x11]
debug1: confirm x11
Xlib: connection to "localhost:10.0" refused by server
Xlib: Invalid MIT-MAGIC-COOKIE-1 keydebug1: channel 1: free: x11, nchannels 2

Error: Can't open display: localhost:10.0
antony@wakeman:~$