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XEmacs / etc / gnuserv.1

.TH GNUSERV 1 "" "XEmacs Server"
.UC 4
.SH NAME
gnuserv, gnuclient, gnuattach, gnudoit \- Server and Clients for XEmacs
.SH SYNOPSIS
.B gnuclient
[-q] [[-h hostname] [-p port] [-r pathname]] [[+line] path] ...
.br
.B gnuattach
[[-h hostname] [-p port] [-r pathname]] [[+line] path] ...
.br
.B gnudoit 
[-q] [[-h hostname] [-p port]] [sexpr] ...
.br
.B gnuserv
.SH DESCRIPTION

.PP
\fIgnuclient\fP allows the user to request a running XEmacs process to edit
the named files or directories (typically in a newly created X frame).
.PP
\fIgnuattach\fP allows the user to request a running XEmacs process to edit
the named files or directories in the current TTY connection.  One typical
use for this is with a dialup connection to a machine on which an XEmacs
process is currently running.
.PP
\fIgnudoit\fP allows the user to request a running XEmacs process to
evaluate the given arguments inside a progn LISP form.
.PP
\fIgnuserv\fP is the server program that is set running by XEmacs to handle
all incoming and outgoing requests. It is not usually invoked directly, but is
started from XEmacs by loading the \fIgnuserv\fP package and evaluating 
the LISP form (gnuserv-start). 
.SH OPTIONS
.TP 8
.BI \-q
This option informs both \fIgnuclient\fP and \fIgnudoit\fP to exit once
connection has been made with the XEmacs process.  Normally \fIgnuclient\fP
waits until all of the files on the command line have been finished with
(their buffers killed) by the XEmacs process, and \fIgnudoit\fP normally
waits around for evaluation of its arguments by the XEmacs process, and
prints the results or error conditions.  This option does not exist for
\fIgnuattach\fP because it does not make sense -- XEmacs and the shell
would fight for input and would screw up each other's output.
.TP 8
.BI \-h " hostname"
Used only with Internet-domain sockets, this option specifies the host
machine which should be running \fIgnuserv\fP.  If this option is not
specified then the value of the environment variable GNU_HOST is used
if set.  If no hostname is specified, and the GNU_HOST variable is not
set, an internet connection will not be attempted.  N\.B.: \fIgnuserv\fP
does NOT allow internet connections unless the GNU_SECURE variable has
been specified and points at a file listing all trusted hosts. (See
SECURITY below.)

.br
Note that an internet address may be specified instead of a hostname which can
speed up connections to the server by quite a bit, especially if the client
machine is running YP.

.br
Note also that a hostname of \fBunix\fP can be used to specify that
the connection to the server should use a Unix-domain socket (if
supported) rather than an Internet-domain socket.
.TP 8
.BI \-p " port"
Used only with Internet-domain sockets, this option specifies the
service port used to communicate between server and clients.  If this
option is not specified, then the value of the environment variable
GNU_PORT is used, if set, otherwise a service called ``gnuserv'' is
looked up in the services database.  Finally, if no other value can be
found for the port, then a default port is used which is usually 21490
+ uid.
.br
Note that since \fIgnuserv\fP doesn't allow command-line options, the port for
it will have to be specified via one of the alternative methods.
.TP 8
.BI \-r " pathname"
Used only with Internet-domain sockets, the pathname argument may be
needed to inform XEmacs how to reach the root directory of a remote
machine.  \fIgnuclient\fP and \fIgnuattach\fP prepend this string to
each path argument given.  For example, if you were trying to edit a
file on a client machine called otter, whose root directory was
accessible from the server machine via the path /net/otter, then this
argument should be set to '/net/otter'.  If this option is omitted,
then the value is taken from the environment variable GNU_NODE, if
set, or the empty string otherwise.
.TP 8
.BI "path"
This is the path of the file to be edited.  If the file is a directory, then
the directory browsers dired or monkey are usually invoked instead.
.TP 8
.BI "sexpr"
This is part of an XEmacs LISP expression to evaluate.  All the sexprs are
concatenated together and wrapped in a progn form before sending to
XEmacs.  If no sexpr is supplied on the  \fIgnudoit\fP commandline,
\fIgnudoit\fP will read the sexpr to be evaluated from standard input.

.PP
.SH SETUP
\fIgnuserv\fP is packaged standardly with recent versions of XEmacs.
Therefore, you should be able to start the server simply by evaluating
the XEmacs Lisp form (gnuserv-start), or equivalently by typing
`M-x gnuserv-start'.
.SH EXAMPLE
.RS 4
gnudoit -q '(mh-smail)'
.br
gnuclient -h cuckoo -r /ange@otter: /tmp/*
.br
gnuattach ../src/listproc.c
.RE

.SH SYSV IPC 
SysV IPC is used to communicate between \fIgnuclient\fP,
\fIgnuattach\fP, \fIgnudoit\fP and \fIgnuserv\fP if the symbol
SYSV_IPC is defined at the top of gnuserv.h. This is incompatible with
both Unix-domain and Internet-domain socket communication as described
below. A file called /tmp/gsrv??? is created as a key for the message
queue, and if removed will cause the communication between server and
client to fail until the server is restarted.
.SH UNIX-DOMAIN SOCKETS
A Unix-domain socket is used to communicate between \fIgnuclient\fP,
\fIgnuattach\fP, \fIgnudoit\fP and \fIgnuserv\fP if the symbol
UNIX_DOMAIN_SOCKETS is defined at the top of gnuserv.h.  A file called
/tmp/gsrvdir????/gsrv is created for communication and if deleted will
cause communication between server and client to fail.  Only the user
running gnuserv will be able to connect to the socket.
.SH INTERNET-DOMAIN SOCKETS
Internet-domain sockets are used to communicate between
\fIgnuclient\fP, \fIgnuattach\fP, \fIgnudoit\fP and \fIgnuserv\fP if
the symbol INTERNET_DOMAIN_SOCKETS is defined at the top of
gnuserv.h. Both Internet-domain and Unix-domain sockets can be used at
the same time. If a hostname is specified via -h or via the GNU_HOST
environment variable, \fIgnudoit\fP, \fIgnuclient\fP and
\fIgnuattach\fP establish connections using an internet domain
socket. If not, a local connection is attempted via either a
unix-domain socket or SYSV IPC."
.SH SECURITY
Using Internet-domain sockets, a more robust form of security is
needed that wasn't necessary with either Unix-domain sockets or SysV
IPC. Currently, two authentication protocols are supported to provide
this: MIT-MAGIC-COOKIE-1 (based on the X11 xauth(1) program) and a
simple host-based access control mechanism, hereafter called
GNUSERV-1. The GNUSERV-1 protocol is always available, whereas support
for MIT-MAGIC-COOKIE-1 may or may not have been enabled (via a #define
at the top of gnuserv.h) at compile-time.
.PP
\fIgnuserv\fP, using GNUSERV-1, performs a limited form of access
control at the machine level. By default no internet-domain socket is
opened.  If the variable GNU_SECURE can be found in \fIgnuserv\fP's
environment, and it names a readable filename, then this file is
opened and assumed to be a list of hosts, one per line, from which the
server will allow requests. Connections from any other host will be
rejected. Even the machine on which \fIgnuserv\fP is running is not
permitted to make connections via the internet socket unless its
hostname is explicitly specified in this file.  Note that a host may
be either a numeric IP address or a hostname, and that
.I any
user on an approved host may connect to your gnuserv and execute arbitrary
elisp (e.g., delete all your files).
If this file contains a lot of
hostnames then the server may take quite a time to start up.
.PP
When the MIT-MAGIC-COOKIE-1 protocol is enabled, an internet socket
\fIis\fP opened by default. \fIgnuserv\fP will accept a connection from
any host, and will wait for a "magic cookie" (essentially, a password)
to be presented by the client. If the client doesn't present the
cookie, or if the cookie is wrong, the authentication of the client is
considered to have failed. At this point. \fIgnuserv\fP falls back to
the GNUSERV-1 protocol; If the client is calling from a host listed in
the GNU_SECURE file, the connection will be accepted, otherwise it
will be rejected. 
.TP 4
.I  Using MIT-MAGIC-COOKIE-1 authentication
When the \fIgnuserv\fP server is started, it looks for a cookie
defined for display 999 on the machine where it is running. If the
cookie is found, it will be stored for use as the authentication
cookie. These cookies are defined in an authorization file (usually
~/.Xauthority) that is manipulated by the X11 xauth(1) program. For
example, a machine "kali" which runs an emacs that invokes
\fIgnuserv\fP should respond as follows (at the shell prompt) when set
up correctly.
.PP
.RS 8
kali% xauth list
.br
GS65.SP.CS.CMU.EDU:0  MIT-MAGIC-COOKIE-1  11223344
.br
KALI.FTM.CS.CMU.EDU:999  MIT-MAGIC-COOKIE-1  1234
.RE
.PP
.RS 4
In the above case, the authorization file defines two cookies. The
second one, defined for screen 999 on the server machine, is used for
gnuserv authentication. 
.PP
On the client machine's side, the authorization file must contain an
identical line, specifying the 
.I server's 
cookie. In other words, on a machine "foobar" which wishes to connect
to "kali,"  the `xauth list' output should contain the line:
.PP
.RS 4
KALI.FTM.CS.CMU.EDU:999  MIT-MAGIC-COOKIE-1  1234
.RE
.PP
For more information on authorization files, take a look at the
xauth(1X11) man page, or invoke xauth interactively (without any
arguments) and type "help" at the prompt. Remember that case in the
name of the authorization protocol (i.e.`MIT-MAGIC-COOKIE-1') 
.I is
significant!
.RE

.SH FILES
.PP
.TP 8
.B /tmp/gsrv???
(SYSV_IPC only)
.TP 8
.B /tmp/gsrvdir???/gsrv
(unix domain sockets only)
.TP 8
.B ~/.emacs
XEmacs customization file, see xemacs(1).
.SH SEE ALSO
.PP
.TP 8
xauth(1X11), Xsecurity(1X11)
.SH BUGS
.PP 
Ctrl-D's occurring in gnudoit input strings won't be handled correctly.
.PP 
NULs occurring in result strings don't get passed back to gnudoit properly.

.SH AUTHOR.
Andy Norman (ange@hplb.hpl.hp.com), based heavily upon
etc/emacsclient.c, etc/server.c and lisp/server.el from the GNU Emacs
18.52 distribution.  Various modifications from Bob Weiner (weiner@mot.com),
Darrell Kindred (dkindred@cmu.edu), Arup Mukherjee (arup@cmu.edu), and
Ben Wing (wing@666.com).
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