MAN page from Old RedHat 5.X dxpc-3.7.0-1.i386.rpm

DXPC

Section: User Commands (1)
Updated: Septmber 7, 1997
Index

NAME

dxpc - Differential X Protocol Compressor

RELEASE

3.7.0

SYNOPSIS

Server Proxy mode:
dxpc[-s(1|2)][-p portnumber][-f|-k][-l filename][-w|clienthostname]

Client Proxy mode:
dxpc[-s(1|2)][-p portnumber][-d displaynum][-u][-t][-f|-k][-l filename][-w serverhostname]

DESCRIPTION

dxpc is an X protocol compressor designed to improve thespeed of X11 applications run over low-bandwidth links (such as dialupPPP connections).

dxpc must be run at both ends of a low-bandwidth link. On the hostwhere the real X server is, dxpc runs in "Server Proxy" mode. On thehost at the other end of the link, dxpc runs in "Client Proxy" mode.The Client Proxy dxpc must be started first. When the Server Proxydxpc is started, it connects to the Client Proxy. (Note that versionsof dxpc before 3.3.1 used the opposite convention.) If either of thetwo communicating dxpc instances is subsequently terminated, the otherone automatically shuts down.

The Client Proxy mimics an X server. X client applications connectto the Client Proxy using display "unix:8" (or "<hostname>:8"; dxpcsupports both UNIX domain and TCP sockets). The Client Proxy receivesX requests from the application, compresses them, and sends them tothe Server Proxy. The Server Proxy uncompresses the requests andsends them to the real X server. Similarly, the Server Proxy receivesX events, replies, and errors from the real X server. It compressesthese messages and sends them to the Client Proxy, which uncompressesthem and sends them to the client application.

The compression performance of dxpc depends upon the types of X applicationsbeing run. For many applications, dxpc achieves between 3:1 and 6:1compression of the X protocol traffic.

Options

-d displaynum: This option specifies the number of the X display that dxpc imitates.The default value is 8. (This option is ignored in Server Proxy mode.)
-f: This option tells dxpc to fork and run as a daemon process. All subsequentnon-error output is suppressed, including statistics reports. The daemoncan be killed by use of the -k option.
-k: This option tells dxpc to read a pid from the lockfile in the user's homedirectory and then send a SIGKILL to the old process. It does some errorchecking to try to ensure that the file contains a valid pid file (andnothing else). The pidfile will exist only if dxpc was started with the-f option.
-l: This option is used to tell dxpc to write messages and statistics to alogfile. Very useful with the -f option.
-p portnumber: This option specifies the TCP port number to be used for communication betweenthe Client Proxy and the Server Proxy. The default value is 4000.
-s(1|2): Print a report on dxpc's compression performance for an X application whenthe application exits. In Client Proxy mode, dxpc displays a report on thecompression of messages generated by the X client. In Server Proxy mode,dxpc displays a report on the compression of messages generated by the Xserver. The -s1 option yields a simple report that provides theoverall compression ratio. The -s2 option yields a far more detailedreport on the compression ratios achieved for all the individual messagetypes in the X protocol. The -s2 option is the "hacker option"; mostpeople will probably want the -s1 report instead.
-u -t: Normally, dxpc in Client Proxy mode imitates an X display, :8 by default,by listening on both a UNIX domain socket and a TCP socket. The -uoption tells it not to use the UNIX domain port, and the -t optiontells it not to use the TCP port. (These options are ignored in ServerProxy mode.)
-v: This option tells dxpc to print out its version number and copyrightmessage and exit.
-w: Use of this option swaps the connection sequence. That is, the client willinitiate the connection to the server. Thus, instead of starting theclient like dxpc -f and the server as dxpc -f workserver, youcan start the client as dxpc -w -f homepc and the server as dxpc-w -f. This option is intended to be useful for people running theclient proxy on a machine behind a firewall.
clienthostname: This argument must be used in Server Proxy mode to tell dxpc the hostname orIP address of the machine where other dxpc (the one in Client Proxy mode) isrunning. (Note that the presence of this argument is what puts dxpc in ServerProxy mode. If this argument is not used, dxpc runs in Client Proxy mode.)

EXAMPLES

Assume that you're running a real X server on the console of a localworkstation called homepc, and that you want to run some X applications ona remote system called workserver and have them display on the console ofthe local system.

On workserver, run

        $ export DISPLAY=homepc:0    $ dxpc -f    $ export DISPLAY=unix:8

On homepc, run

    $ export DISPLAY=unix:0    $ dxpc -f workserver

Now on workserver,

    $ xterm&    $ xemacs&    etc...

DXPC AND XAUTH

If you use X authorization, with a .Xauthority file on the workstationwhere your real X server runs, you'll need to set up a .Xauthority fileon the host where the ClientProxy runs. One way to do this is:

Copy your ~/.Xauthority file from the host where the real X serverruns to the host where the Client Proxy runs.

Run

    xauth list

to see the authorization keys. There should be one for yourreal X display. It will look something like this:

    <hostname>/unix:0   MIT-MAGIC-COOKIE-1   <hex string>

On the host where the Client Proxy is located, add a new entry tothe .Xauthority file with the display name of the fake X server (theDISPLAY where the Client Proxy is listening) and all of the othervalues from the entry for the real X display. The xauth "add"command can be used, like this:

    xauth add <hostname>/unix:8 MIT-MAGIC-COOKIE-1  <hex string>

where <hostname> is the name of the host where the Client Proxy is runningand <hex string> has the same value as the <hex string> obtained forthe real X display in step 2. Once you do this, you should beable to run X clients through dxpc successfully.

AUTHOR

Brian Pane

MAINTAINER

Zachary Vonler (lightbornAATTmail.utexas.edu)

ACKNOWLEDGMENTS

dxpc has adopted many good ideas from the HBX and FHBXsystems (http://www.cs.dartmouth.edu/~jmd/decs/DECSpage.html).

Thanks to all of the users of dxpc who have contributed feedback andsuggestions.

This document was created byman2html,using the manual pages.