Added comments, use 'global' and change prompt to "ftp.py> "
diff --git a/Demo/sockets/ftp.py b/Demo/sockets/ftp.py
index ff15642..f5bbdf5 100755
--- a/Demo/sockets/ftp.py
+++ b/Demo/sockets/ftp.py
@@ -4,6 +4,18 @@
# 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...
+#
+# How it works (assuming you've read the RFC):
+#
+# User commands are passed uninterpreted to the server. However, the
+# user never needs to send a PORT command. Rather, the client opens a
+# port right away and sends the appropriate PORT command to the server.
+# When a response code 150 is received, this port is used to receive
+# the data (which is written to stdout in this version), and when the
+# data is exhausted, a new port is opened and a corresponding PORT
+# command sent. In order to avoid errors when reusing ports quickly
+# (and because there is no s.getsockname() method in Python yet) we
+# cycle through a number of ports in the 50000 range.
import sys, posix, string
@@ -60,12 +72,12 @@
# (Cycle through a number of ports to avoid problems with reusing
# a port within a short time.)
#
-cycle = [0]
+nextport = 0
#
def newdataport(s, f):
- port = cycle[0]
- cycle[0] = (port+1) % 16
- port = port + FTP_DATA_PORT
+ global nextport
+ port = nextport + FTP_DATA_PORT
+ nextport = (nextport+1) % 16
r = socket(AF_INET, SOCK_STREAM)
r.bind(gethostbyname(gethostname()), port)
r.listen(0)
@@ -122,7 +134,7 @@
#
def getcommand():
try:
- return raw_input('ftp> ')
+ return raw_input('ftp.py> ')
except EOFError:
return ''