Filesystem, RCS and CVS client and server classes================================================= *** See the security warning at the end of this file! *** This directory contains various modules and classes that supportremote file system operations. CVS stuff--------- rcvs			Script to put in your bin directoryrcvs.py			Remote CVS client command line interface cvslib.py		CVS admin files classes (used by rrcs)cvslock.py		CVS locking algorithms RCS stuff--------- rrcs			Script to put in your bin directoryrrcs.py			Remote RCS client command line interface rcsclient.py		Return an RCSProxyClient instance			(has reasonable default server/port/directory) RCSProxy.py		RCS proxy and server classes (on top of rcslib.py) rcslib.py		Local-only RCS base class (affects stdout &			local work files) FSProxy stuff------------- sumtree.py		Old demo for FSProxycmptree.py		First FSProxy client (used to sync from the Mac)FSProxy.py		Filesystem interface classes Generic client/server stuff--------------------------- client.py		Client classserver.py		Server class security.py		Security mix-in class (not very secure I think) Other generic stuff------------------- cmdfw.py		CommandFrameWork class			(used by rcvs, should be used by rrcs as well)  Client/Server operation----------------------- The Client and Server classes implement a simple-minded RPC protocol,using Python's pickle module to transfer arguments, return values andexceptions with the most generality.  The Server class is instantiatedwith a port number on which it should listen for requests; the Clientclass is instantiated with a host name and a port number where itshould connect to.  Once a client is connected, a TCP connection ismaintained between client and server. The Server class currently handles only one connection at a time;however it could be rewritten to allow various modes of operations,using multiple threads or processes or the select() system call asdesired to serve multiple clients simultaneously (when using select(),still handling one request at a time).  This would not requirerewriting of the Client class.  It may also be possible to adapt thecode to use UDP instead of TCP, but then both classes will have to berewritten (and unless extensive acknowlegements and request serialnumbers are used, the server should handle duplicate requests, so itssemantics should be idempotent -- shrudder). Even though the FSProxy and RCSProxy modules define client classes,the client class is fully generic -- what methods it supports isdetermined entirely by the server.  The server class, however, must bederived from.  This is generally done as follows: 	from server import Server	from client import Client 	# Define a class that performs the operations locally	class MyClassLocal:		def __init__(self): ...		def _close(self): ... 	# Derive a server class using multiple inheritance	class MyClassServer(MyClassLocal, Server):		def __init__(self, address):			# Must initialize MyClassLocal as well as Server			MyClassLocal.__init__(self)			Server.__init__(self, address)		def _close(self):			Server._close()			MyClassLocal._close() 	# A dummy client class	class MyClassClient(Client): pass Note that because MyClassLocal isn't used in the definition ofMyClassClient, it would actually be better to place it in a separatemodule so the definition of MyClassLocal isn't executed when we onlyinstantiate a client. The modules client and server should probably be renamed to Client andServer in order to match the class names.  *** Security warning: this version requires that you have a file$HOME/.python_keyfile at the server and client side containing twocomma- separated numbers.  The security system at the moment makes noguarantees of actuallng being secure -- however it requires that thekey file exists and contains the same numbers at both ends for this towork.  (You can specify an alternative keyfile in $PYTHON_KEYFILE).Have a look at the Security class in security.py for details;basically, if the key file contains (x, y), then the security serverclass chooses a random number z (the challenge) in the range10..100000 and the client must be able to produce pow(z, x, y)(i.e. z**x mod y).