hostname:displaynumber.screennumber
This information is used by the application to determine
how it should connect to the server and which screen it should use by default
(on displays with multiple monitors): hostname The hostname
specifies the name of the machine to which the display is physically connected.
If the hostname is not given, the most efficient way of communicating to
a server on the same machine will be used. displaynumber
The phrase "display" is usually used to refer to collection
of monitors that share a common keyboard and pointer (mouse, tablet, etc.).
Most workstations tend to only have one keyboard, and therefore, only one
display. Larger, multi-user systems, however, will frequently have several
displays so that more than one person can be doing graphics work at once.
To avoid confusion, each display on a machine is assigned
a displaynumber (beginning at 0) when the X server for that
display is started. The display number must always be given in a display
name.
screennumber
Some displays share a single keyboard and pointer among
two or more monitors. Since each monitor has its own set of windows, each
screen is assigned a screen number (beginning at 0) when
the X server for that display is started. If the screen number is not given,
then screen 0 will be used.
On POSIX systems, the default display name is stored in
your DISPLAY environment variable. This variable is set automatically
by the xterm terminal emulator. However, when you log into
another machine on a network, you'll need to set DISPLAY by hand to point
to your display. For example,
% setenv DISPLAY myws:0 $ DISPLAY=myws:0;
export DISPLAY
The xon script can be used to start an X program
on a remote machine; it automatically sets the DISPLAY variable correctly.
Finally, most X programs accept a command line option of -display
displayname
to temporarily override the contents of DISPLAY. This is most commonly
used to pop windows on another person's screen or as part of a "remote
shell" command to start an xterm pointing back to your display.
For example,
% xeyes -display joesws:0 -geometry 1000x1000+0+0
% rsh big xterm -display myws:0 -ls </dev/null &
X servers listen for connections on a variety of different
communications channels (network byte streams, shared memory, etc.). Since
there can be more than one way of contacting a given server, The hostname
part of the display name is used to determine the type of channel (also
called a transport layer) to be used. X servers generally support the following
types of connections:
local
The hostname part of the display name should be the empty
string.
For example:
:0, :1, and :0.1.
The most efficient local transport will be chosen.
TCP/IP
The hostname part of the display name should be the server
machine's IP address name. Full Internet names, abbreviated names, and
IP addresses are all allowed. For example:
expo.lcs.mit.edu:0,
expo:0,
18.30.0.212:0,
bigmachine:1,
and hydra:0.1. DECnet The hostname part of
the display name should be the server machine's nodename followed by two
colons instead of one.
For example:
myws::0,
big::1,
and hydra::0.1.
