| # 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... |
| # |
| # 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 |
| 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.) |
| # |
| nextport = 0 |
| # |
| def newdataport(s, f): |
| global nextport |
| port = nextport + FTP_DATA_PORT |
| nextport = (nextport+1) % 16 |
| r = socket(AF_INET, SOCK_STREAM) |
| r.bind(gethostbyname(gethostname()), port) |
| r.listen(1) |
| 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 and line[3:4] != '-': 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: |
| while 1: |
| line = raw_input('ftp.py> ') |
| if line: return line |
| except EOFError: |
| return '' |
| |
| |
| # Call the main program. |
| # |
| main() |