1 Filesystem, RCS and CVS client and server classes 2 ================================================= 3 4 *** See the security warning at the end of this file! *** 5 6 This directory contains various modules and classes that support 7 remote file system operations. 8 9 CVS stuff 10 --------- 11 12 rcvs Script to put in your bin directory 13 rcvs.py Remote CVS client command line interface 14 15 cvslib.py CVS admin files classes (used by rrcs) 16 cvslock.py CVS locking algorithms 17 18 RCS stuff 19 --------- 20 21 rrcs Script to put in your bin directory 22 rrcs.py Remote RCS client command line interface 23 24 rcsclient.py Return an RCSProxyClient instance 25 (has reasonable default server/port/directory) 26 27 RCSProxy.py RCS proxy and server classes (on top of rcslib.py) 28 29 rcslib.py Local-only RCS base class (affects stdout & 30 local work files) 31 32 FSProxy stuff 33 ------------- 34 35 sumtree.py Old demo for FSProxy 36 cmptree.py First FSProxy client (used to sync from the Mac) 37 FSProxy.py Filesystem interface classes 38 39 Generic client/server stuff 40 --------------------------- 41 42 client.py Client class 43 server.py Server class 44 45 security.py Security mix-in class (not very secure I think) 46 47 Other generic stuff 48 ------------------- 49 50 cmdfw.py CommandFrameWork class 51 (used by rcvs, should be used by rrcs as well) 52 53 54 Client/Server operation 55 ----------------------- 56 57 The Client and Server classes implement a simple-minded RPC protocol, 58 using Python's pickle module to transfer arguments, return values and 59 exceptions with the most generality. The Server class is instantiated 60 with a port number on which it should listen for requests; the Client 61 class is instantiated with a host name and a port number where it 62 should connect to. Once a client is connected, a TCP connection is 63 maintained between client and server. 64 65 The Server class currently handles only one connection at a time; 66 however it could be rewritten to allow various modes of operations, 67 using multiple threads or processes or the select() system call as 68 desired to serve multiple clients simultaneously (when using select(), 69 still handling one request at a time). This would not require 70 rewriting of the Client class. It may also be possible to adapt the 71 code to use UDP instead of TCP, but then both classes will have to be 72 rewritten (and unless extensive acknowlegements and request serial 73 numbers are used, the server should handle duplicate requests, so its 74 semantics should be idempotent -- shrudder). 75 76 Even though the FSProxy and RCSProxy modules define client classes, 77 the client class is fully generic -- what methods it supports is 78 determined entirely by the server. The server class, however, must be 79 derived from. This is generally done as follows: 80 81 from server import Server 82 from client import Client 83 84 # Define a class that performs the operations locally 85 class MyClassLocal: 86 def __init__(self): ... 87 def _close(self): ... 88 89 # Derive a server class using multiple inheritance 90 class MyClassServer(MyClassLocal, Server): 91 def __init__(self, address): 92 # Must initialize MyClassLocal as well as Server 93 MyClassLocal.__init__(self) 94 Server.__init__(self, address) 95 def _close(self): 96 Server._close() 97 MyClassLocal._close() 98 99 # A dummy client class 100 class MyClassClient(Client): pass 101 102 Note that because MyClassLocal isn't used in the definition of 103 MyClassClient, it would actually be better to place it in a separate 104 module so the definition of MyClassLocal isn't executed when we only 105 instantiate a client. 106 107 The modules client and server should probably be renamed to Client and 108 Server in order to match the class names. 109 110 111 *** Security warning: this version requires that you have a file 112 $HOME/.python_keyfile at the server and client side containing two 113 comma- separated numbers. The security system at the moment makes no 114 guarantees of actuallng being secure -- however it requires that the 115 key file exists and contains the same numbers at both ends for this to 116 work. (You can specify an alternative keyfile in $PYTHON_KEYFILE). 117 Have a look at the Security class in security.py for details; 118 basically, if the key file contains (x, y), then the security server 119 class chooses a random number z (the challenge) in the range 120 10..100000 and the client must be able to produce pow(z, x, y) 121 (i.e. z**x mod y). 122
