Initial revision

Demo/sockets/ftp.py

@@ -0,0 +1,132 @@
+# A simple FTP client.
+#
+# The information to write this program was gathered from RFC 959,
+# but this is not a complete implementation!  Yet it shows how a simple
+# FTP client can be built, and you are welcome to extend it to suit
+# it to your needs...
+
+
+import sys, posix, string
+from socket import *
+
+
+BUFSIZE = 1024
+
+# Default port numbers used by the FTP protocol.
+#
+FTP_PORT = 21
+FTP_DATA_PORT = FTP_PORT - 1
+
+# Change the data port to something not needing root permissions.
+#
+FTP_DATA_PORT = FTP_DATA_PORT + 50000
+
+
+# Main program (called at the end of this file).
+#
+def main():
+	hostname = sys.argv[1]
+	control(hostname)
+
+
+# Control process (user interface and user protocol interpreter).
+#
+def control(hostname):
+	#
+	# Create control connection
+	#
+	s = socket(AF_INET, SOCK_STREAM)
+	s.connect(hostname, FTP_PORT)
+	f = s.makefile('r') # Reading the replies is easier from a file...
+	#
+	# Control loop
+	#
+	r = None
+	while 1:
+		code = getreply(f)
+		if code in ('221', 'EOF'): break
+		if code == '150':
+			getdata(r)
+			code = getreply(f)
+			r = None
+		if not r:
+			r = newdataport(s, f)
+		cmd = getcommand()
+		if not cmd: break
+		s.send(cmd + '\r\n')
+
+
+# Create a new data port and send a PORT command to the server for it.
+# (Cycle through a number of ports to avoid problems with reusing
+# a port within a short time.)
+#
+cycle = [0]
+#
+def newdataport(s, f):
+	port = cycle[0]
+	cycle[0] = (port+1) % 16
+	port = port + FTP_DATA_PORT
+	r = socket(AF_INET, SOCK_STREAM)
+	r.bind(gethostbyname(gethostname()), port)
+	r.listen(0)
+	sendportcmd(s, f, port)
+	return r
+
+
+# Send an appropriate port command.
+#
+def sendportcmd(s, f, port):
+	hostname = gethostname()
+	hostaddr = gethostbyname(hostname)
+	hbytes = string.splitfields(hostaddr, '.')
+	pbytes = [`port/256`, `port%256`]
+	bytes = hbytes + pbytes
+	cmd = 'PORT ' + string.joinfields(bytes, ',')
+	s.send(cmd + '\r\n')
+	code = getreply(f)
+
+
+# Process an ftp reply and return the 3-digit reply code (as a string).
+# The reply should be a line of text starting with a 3-digit number.
+# If the 4th char is '-', it is a multi-line reply and is
+# terminate by a line starting with the same 3-digit number.
+# Any text while receiving the reply is echoed to the file.
+#
+def getreply(f):
+	line = f.readline()
+	if not line: return 'EOF'
+	print line,
+	code = line[:3]
+	if line[3:4] == '-':
+		while 1:
+			line = f.readline()
+			if not line: break # Really an error
+			print line,
+			if line[:3] == code: break
+	return code
+
+
+# Get the data from the data connection.
+#
+def getdata(r):
+	print '(accepting data connection)'
+	conn, host = r.accept()
+	print '(data connection accepted)'
+	while 1:
+		data = conn.recv(BUFSIZE)
+		if not data: break
+		sys.stdout.write(data)
+	print '(end of data connection)'
+
+# Get a command from the user.
+#
+def getcommand():
+	try:
+		return raw_input('ftp> ')
+	except EOFError:
+		return ''
+
+
+# Call the main program.
+#
+main()