Telling a client to display across the network in this way does not address any of the
three remote access challenges (Section 13.7): no attempt is made to reduce network
bandwidth or latency requirements, no authentication is performed, and the data can
be readily intercepted on the network.
SUSE uses KDM as the default display manager and has configured it
so that the local X servers accept connections only through Unix
domain sockets and not through TCP/IP. This prevents the use of
remote clients. To enable remote connections, remove the -nolisten
tcp options from /opt/kde3/share/config/kdm and restart KDM.
13.3 Enabling Remote Sessions
Display managers??”such as XDM, GDM, and KDM??”manage local X displays, but
are also capable of managing remote displays through a protocol called X Display
Manager Control Protocol (XDMCP).
XDMCP enables a user to remotely log in to a server using a graphical authentication
dialog. After the user has logged in, a normal session is started (including the
window manager, desktop environment, and so forth), as though the user was using
a local X server.
XDMCP uses both TCP and UDP on port 177. It is disabled by default in most distributions
and must be enabled before remote session can be used; the procedure to
enable it varies according to the display manager in use.
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