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Guido van Rossumb83ec8f1992-05-19 13:52:02 +00001# A simple FTP client.
2#
3# The information to write this program was gathered from RFC 959,
4# but this is not a complete implementation! Yet it shows how a simple
5# FTP client can be built, and you are welcome to extend it to suit
6# it to your needs...
Guido van Rossumbfef4a01992-11-16 16:55:11 +00007#
8# How it works (assuming you've read the RFC):
9#
10# User commands are passed uninterpreted to the server. However, the
11# user never needs to send a PORT command. Rather, the client opens a
12# port right away and sends the appropriate PORT command to the server.
13# When a response code 150 is received, this port is used to receive
14# the data (which is written to stdout in this version), and when the
15# data is exhausted, a new port is opened and a corresponding PORT
16# command sent. In order to avoid errors when reusing ports quickly
17# (and because there is no s.getsockname() method in Python yet) we
18# cycle through a number of ports in the 50000 range.
Guido van Rossumb83ec8f1992-05-19 13:52:02 +000019
20
21import sys, posix, string
22from socket import *
23
24
25BUFSIZE = 1024
26
27# Default port numbers used by the FTP protocol.
28#
29FTP_PORT = 21
30FTP_DATA_PORT = FTP_PORT - 1
31
32# Change the data port to something not needing root permissions.
33#
34FTP_DATA_PORT = FTP_DATA_PORT + 50000
35
36
37# Main program (called at the end of this file).
38#
39def main():
40 hostname = sys.argv[1]
41 control(hostname)
42
43
44# Control process (user interface and user protocol interpreter).
45#
46def control(hostname):
47 #
48 # Create control connection
49 #
50 s = socket(AF_INET, SOCK_STREAM)
Jeremy Hyltona8d30d52000-08-25 15:38:41 +000051 s.connect((hostname, FTP_PORT))
Guido van Rossumb83ec8f1992-05-19 13:52:02 +000052 f = s.makefile('r') # Reading the replies is easier from a file...
53 #
54 # Control loop
55 #
56 r = None
57 while 1:
58 code = getreply(f)
59 if code in ('221', 'EOF'): break
60 if code == '150':
61 getdata(r)
62 code = getreply(f)
63 r = None
64 if not r:
65 r = newdataport(s, f)
66 cmd = getcommand()
67 if not cmd: break
68 s.send(cmd + '\r\n')
69
70
71# Create a new data port and send a PORT command to the server for it.
72# (Cycle through a number of ports to avoid problems with reusing
73# a port within a short time.)
74#
Guido van Rossumbfef4a01992-11-16 16:55:11 +000075nextport = 0
Guido van Rossumb83ec8f1992-05-19 13:52:02 +000076#
77def newdataport(s, f):
Guido van Rossumbfef4a01992-11-16 16:55:11 +000078 global nextport
79 port = nextport + FTP_DATA_PORT
80 nextport = (nextport+1) % 16
Guido van Rossumb83ec8f1992-05-19 13:52:02 +000081 r = socket(AF_INET, SOCK_STREAM)
Jeremy Hyltona8d30d52000-08-25 15:38:41 +000082 r.bind((gethostbyname(gethostname()), port))
Guido van Rossum749908b1994-02-28 09:25:38 +000083 r.listen(1)
Guido van Rossumb83ec8f1992-05-19 13:52:02 +000084 sendportcmd(s, f, port)
85 return r
86
87
88# Send an appropriate port command.
89#
90def sendportcmd(s, f, port):
91 hostname = gethostname()
92 hostaddr = gethostbyname(hostname)
93 hbytes = string.splitfields(hostaddr, '.')
94 pbytes = [`port/256`, `port%256`]
95 bytes = hbytes + pbytes
96 cmd = 'PORT ' + string.joinfields(bytes, ',')
97 s.send(cmd + '\r\n')
98 code = getreply(f)
99
100
101# Process an ftp reply and return the 3-digit reply code (as a string).
102# The reply should be a line of text starting with a 3-digit number.
103# If the 4th char is '-', it is a multi-line reply and is
104# terminate by a line starting with the same 3-digit number.
105# Any text while receiving the reply is echoed to the file.
106#
107def getreply(f):
108 line = f.readline()
109 if not line: return 'EOF'
110 print line,
111 code = line[:3]
112 if line[3:4] == '-':
113 while 1:
114 line = f.readline()
115 if not line: break # Really an error
116 print line,
Guido van Rossum4f9181e1995-01-12 12:42:09 +0000117 if line[:3] == code and line[3:4] != '-': break
Guido van Rossumb83ec8f1992-05-19 13:52:02 +0000118 return code
119
120
121# Get the data from the data connection.
122#
123def getdata(r):
124 print '(accepting data connection)'
125 conn, host = r.accept()
126 print '(data connection accepted)'
127 while 1:
128 data = conn.recv(BUFSIZE)
129 if not data: break
130 sys.stdout.write(data)
131 print '(end of data connection)'
132
133# Get a command from the user.
134#
135def getcommand():
136 try:
Guido van Rossum4f9181e1995-01-12 12:42:09 +0000137 while 1:
138 line = raw_input('ftp.py> ')
139 if line: return line
Guido van Rossumb83ec8f1992-05-19 13:52:02 +0000140 except EOFError:
141 return ''
142
143
144# Call the main program.
145#
146main()