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lbxproxy - Low BandWidth X proxy


lbxproxy [:<display>] [option]


Applications that would like to take advantage of the Low Bandwidth extension to X (LBX) must make their connections to an lbxproxy. These applications need to know nothing about LBX, they simply connect to the lbxproxy as if were a regular server. The lbxproxy accepts client connections, multiplexes them over a single connection to the X server, and performs various optimizations on the X protocol to make it faster over low bandwidth and/or high latency connections.

With regard to authentication/authorization, lbxproxy simply passes along to the server the credentials presented by the client. Since X clients will connect to lbxproxy, it is important that the user's .Xauthority file contain entries with valid keys associated with the network ID of the proxy. lbxproxy does not get involved with how these entries are added to the .Xauthority file. The user is responsible for setting it up.

The lbxproxy program has various options, all of which are optional.

If :<display> is specified, the proxy will use the given display port when listening for connections. The display port is an offset from port 6000, identical to the way in which regular X display connections are specified. If no port is specified on the command line option, lbxproxy will default to port 63. If the port number that the proxy tries to listen on is in use, the proxy will attempt to use another port number. If the proxy is not using the Proxy Manager and the default port number cannot be used, the port number that is used will be written to stderr.

The other command line options that can be specified are:

Prints a brief help message about the command line options.
-display dpy
Specifies the address of the X server supporting the LBX extension. If this option is not specified, the display is obtained by the DISPLAY environment variable.
-motion count
A limited number of pointer motion events are allowed to be in flight between the server and the proxy at any given time. The maximum number of motion events that can be in flight is set with this option; the default is 8.
-maxservers number
The default behavior of lbxproxy is to manage a single server. However, lbxproxy can manage more than one server. The default maximum number of servers is 20. The number of servers can be overridden by setting the environment variable LBXPROXY_MAXSERVERS to the desired number. The order of precedence from highest to lowest: command line, environment variable, default number.
The default behavior of lbxproxy is to continue running as usual when it's last client exits. The -terminate option will cause lbxproxy to exit when the last client exits. The -reset option will cause lbxproxy to reset itself when the last client exits. Resetting causes lbxproxy to clean up it's state and reconnect to the server.
The default behavior of lbxproxy is to exit when its connection to the server is broken. The -reconnect option will cause lbxproxy to just reset instead (see -reset above) and attempt to reconnect to the server.
Causes all remaining arguments to be ignored.
Disables all LBX optimizations.
Disables stream compression.
Disables delta request substitutions.
Disables usage of tags.
Disables reencoding of graphics requests (not including image related requests).
Disables image compression.
Disables squishing of X events.
Disables short circuiting of InternAtom requests.
Disables reading of the atoms control file. See the section on "Atom Control" for more details.
-atomsfile file
Overrides the default AtomControl file. See the section on "Atom Control" for more details.
Disables GetWindowAttributes/GetGeometry grouping into one round trip.
Disables colormap grabbing.
Disables color name to RGB resolution in proxy.
-rgbfile path
Specifies an alternate RGB database for color name to RGB resolution.
Set the size of the proxy's tag cache (in bytes).
-zlevel level
Set the Zlib compression level (used for stream compression).
default is 6
1 = worst compression, fastest
9 = best compression, slowest
Report stream compression statistics every time the proxy resets or receives a SIGHUP signal.
Don't zero out unused pad bytes in X requests, replies, and events.
Allows cheating on X protocol for the sake of improved performance. The X protocol guarantees that any replies, events or errors generated by a previous request will be sent before those of a later request. This puts substantial restrictions on when lbxproxy can short circuit a request. The -cheaterrors option allows lbxproxy to violate X protocol rules with respect to errors. Use at your own risk.
The -cheatevents option allows lbxproxy to violate X protocol rules with respect to events as well as errors. Use at your own risk.

Atom Control

At startup, lbxproxy "pre-interns" a configurable list of atoms. This allows lbxproxy to intern a group of atoms in a single round trip and immediately store the results in its cache.

While running, lbxproxy uses heuristics to decide when to delay sending window property data to the server. The heuristics depend on the size of the data, the name of the property, and whether a window manager is running through the same lbxproxy.

Atom control is specified in the "AtomControl" file, set up during installation of lbxproxy, with command line overrides.

The file is a simple text file. There are three forms of lines: comments, length control, and name control. Lines starting with a '!' are treated as comments. A line of the form

z length

specifies the minimum length in bytes before property data will be delayed. A line of the form

options atomname

controls the given atom, where options is any combination of the following characters: 'i' means the atom should be pre-interned; and 'w' means data for properties with this name should be delayed only if a window manager is also running through the same lbxproxy.


When the authorization protocol XDM-AUTHORIZATION-1 is used:

A client must be on the same host as lbxproxy for the client to be authorized to connect to the server.

If a client is not on the same host as lbxproxy, the client will not be authorized to connect to the server.

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