Python 使用socket实现ftp 客服端

之前先了解ftp协议，然后解释代码

连接到ftp服务器，得到一个socket（这是一个连接到ftp命令端口socket）
发送必要request
第一步 Connect到服务器后，ftp_socket.recv(1024) 到服务器的欢迎消息(1 中的socket)，不要问为什么，ftp协议规定的，应该是。*注意的是，后面ftp_socket每一次的请求后，都要recv一次，不管你是否全部接受到了都要recv一次，不然可能后面接受不到一些消息。个人觉着这可能是ftp协议的规定：每一次request，都会给client一个response。如果 client没有接受这个response，那么下次的request不会被服务器接受，所以client的recv就会卡住！
第二步就像代码中直到 #LIST 都是用的命令端口。而使用数据端口时，就是用命令端口 ftp_socket.send("PASV ")
new_port = ftp_socket.recv(1024) 使用命令 PASV 请求一个动态的数据端口。
解释我理解的动态数据端口：即你每一次请求到一个数据端口后，你只能使用一次。比如：[ INFO] 2014-11-29 22:25:44,682 [admin] [127.0.0.1] SENT: 227 Entering Passive Mode (127,0,0,1,204,82) 这是ftp服务器端发送的请求(apache ftpserver)，明显括号中是你的ip（我的是本机），然后两个数字。通过查询，你要请求的数据端口：（a,b,c,d,x,y) new_port = x*250+y
剩下的部分就很简单了。在代码中再有点解释（后面附server端log）
最后还应该用发送一个quit命令，告诉server 我的请求完毕了。这里忘了。
一点补充：看到server端log可以发现，服务器每一次的SEND 我们都应该recv一次

#download a folder's files

import socket

class ParseUrl():

"""docstring for ParseUrl"""

def __init__(self, url):

self.url = url

self.method = ""

self.host = ""

self.port =""

def get_method(self):

method_url = self.url

self.method = method_url.split(":")[0]

print "Request Method:",self.method

return self.method

def get_host(self):

temp_pos = self.url.find("://")

temp_url = self.url[temp_pos+3:]

self.host = temp_url[:temp_url.find(":")]

print "Request Host:",self.host

return self.host

def get_port(self):

tem_url = self.url.split(":")[2]

if tem_url.find("/"):

tem_url = tem_url[:tem_url.find("/")]

print "Request Port:",tem_url

self.port = tem_url

return self.port

def parse(self):

temp_methd = self.get_method()

temp_host = self.get_host()

temp_port = self.get_port()

return temp_methd,temp_host,temp_port

def main():

#ftp url

request_url = "ftp://localhost:2121/"

parse_url = ParseUrl(request_url)

method,host,port = parse_url.parse()

print "method,host,port",method,host,port

#get connection to ftp server

ftp_socket = socket.socket(socket.AF_INET,socket.SOCK_STREAM)

ftp_socket.connect((host,int(port)))

user = "admin "

password = "admin "

print ftp_socket.recv(1024) #这个地方是用来接收欢迎消息

ftp_socket.send("USER "+user)

print ftp_socket.recv(1024)

ftp_socket.send("PASS "+password)

print ftp_socket.recv(1024)

ftp_socket.send("CWD ")

print ftp_socket.recv(1024)

ftp_socket.send("TYPE ASCII ")

print ftp_socket.recv(1024)

ftp_socket.send("SIZE my.txt ")

temp_size = ftp_socket.recv(1024)

file_size = int(temp_size.split(" ")[1])

print file_size

#LIST

ftp_socket.send("PASV ")

new_port = ftp_socket.recv(1024)

print new_port

before_port = ""

temp_port =""

if new_port.startswith("227"):

temp_port = new_port.split(",")[5]

before_port = new_port.split(",")[4]

temp_port = temp_port.replace(") ","")

#get the server's new port

new_request_port = int(before_port)*256+int(temp_port)

# connect to the server's new port

ftp_data_socket = socket.socket(socket.AF_INET,socket.SOCK_STREAM)

ftp_data_socket.connect((host,new_request_port))

ftp_socket.send("LIST ")

print ftp_data_socket.recv(1024).decode("utf-8")

ftp_socket.recv(1024)

#RETR

ftp_socket.send("PASV ")

new_port = ftp_socket.recv(1024)

print new_port

before_port = ""

temp_port =""

if new_port.startswith("227"):

temp_port = new_port.split(",")[5]

before_port = new_port.split(",")[4]

temp_port = temp_port.replace(") ","")

#get the server's new port

new_request_port = int(before_port)*256+int(temp_port)

# connect to the server's new port

ftp_data_socket = socket.socket(socket.AF_INET,socket.SOCK_STREAM)

ftp_data_socket.connect((host,new_request_port))

ftp_socket.send("RETR my.txt ")

file_content = ftp_data_socket.recv(file_size)

print file_content

download_file = open("my.txt","wb")

download_file.write(file_content)

download_file.close()

#print create_data_connection(ftp_socket,"LIST","",host)

if __name__ == '__main__':

main()

SERVEER LOG:

[ INFO] 2014-11-29 22:47:55,513 [] [127.0.0.1] CREATED

[ INFO] 2014-11-29 22:47:55,514 [] [127.0.0.1] OPENED

[ INFO] 2014-11-29 22:47:55,515 [] [127.0.0.1] SENT: 220 Service ready for new user.

[ INFO] 2014-11-29 22:47:55,516 [] [127.0.0.1] RECEIVED: USER admin

[ INFO] 2014-11-29 22:47:55,517 [admin] [127.0.0.1] SENT: 331 User name okay, need password for admin.

[ INFO] 2014-11-29 22:47:55,519 [admin] [127.0.0.1] RECEIVED: PASS *****

[ INFO] 2014-11-29 22:47:55,569 [admin] [127.0.0.1] Login success - admin

[ INFO] 2014-11-29 22:47:55,569 [admin] [127.0.0.1] SENT: 230 User logged in, proceed.

[ INFO] 2014-11-29 22:47:55,571 [admin] [127.0.0.1] RECEIVED: CWD

[ INFO] 2014-11-29 22:47:55,571 [admin] [127.0.0.1] SENT: 250 Directory changed to /

[ INFO] 2014-11-29 22:47:55,572 [admin] [127.0.0.1] RECEIVED: TYPE ASCII

[ INFO] 2014-11-29 22:47:55,573 [admin] [127.0.0.1] SENT: 200 Command TYPE okay.

[ INFO] 2014-11-29 22:47:55,574 [admin] [127.0.0.1] RECEIVED: SIZE my.txt

[ INFO] 2014-11-29 22:47:55,574 [admin] [127.0.0.1] SENT: 213 4813

[ INFO] 2014-11-29 22:47:55,575 [admin] [127.0.0.1] RECEIVED: PASV

[ INFO] 2014-11-29 22:47:55,576 [admin] [127.0.0.1] SENT: 227 Entering Passive Mode (127,0,0,1,213,199)

[ INFO] 2014-11-29 22:47:55,579 [admin] [127.0.0.1] RECEIVED: LIST

[ WARN] 2014-11-29 22:47:55,610 [admin] [127.0.0.1] Releasing unreserved passive port: 54727

[ INFO] 2014-11-29 22:47:55,610 [admin] [127.0.0.1] SENT: 150 File status okay; about to open data connection.

[ INFO] 2014-11-29 22:47:55,610 [admin] [127.0.0.1] SENT: 226 Closing data connection.

[ INFO] 2014-11-29 22:47:55,614 [admin] [127.0.0.1] RECEIVED: PASV

[ INFO] 2014-11-29 22:47:55,616 [admin] [127.0.0.1] SENT: 227 Entering Passive Mode (127,0,0,1,213,201)

[ INFO] 2014-11-29 22:47:55,619 [admin] [127.0.0.1] RECEIVED: RETR my.txt

[ INFO] 2014-11-29 22:47:55,621 [admin] [127.0.0.1] File downloaded /my.txt

[ WARN] 2014-11-29 22:47:55,622 [admin] [127.0.0.1] Releasing unreserved passive port: 54729

[ INFO] 2014-11-29 22:47:55,622 [admin] [127.0.0.1] SENT: 150 File status okay; about to open data connection.

[ INFO] 2014-11-29 22:47:55,622 [admin] [127.0.0.1] SENT: 226 Transfer complete.