检索文件时出现错误 运行 FTP.retrbinary
Getting an error running FTP.retrbinary to retrieve a file
我正在使用 pythons ftplib 尝试从远程服务器检索文件（练习项目）。我在发送文件时没有遇到任何问题，但在尝试检索时遇到错误。我正在使用 python 3. 这是我的代码：
from ftplib import FTP
user = 'myusername'
passw = 'mypassw'
url = input('FTP url: ').lower().strip()
ftp = FTP(url) #connect to the host, default port
ftp.login(user, passw) # enters login info
def getfile():
ftp.retrlines('LIST') # List directory contents
filename = input('Name of file: ')
localfile = open(filename, 'wb')
ftp.retrbinary('RETR' + filename, localfile.write, 1024)
localfile.close()
getfile()
这是我得到的错误：
Traceback (most recent call last):
File "C:\Users\User\Desktop\School\python\ftpget.py", line 16, in <module>
getfile()
File "C:\Users\User\Desktop\School\python\ftpget.py", line 13, in getfile
ftp.retrbinary('RETR' + filename, localfile.write, 1024)
File "C:\Python34\lib\ftplib.py", line 441, in retrbinary
with self.transfercmd(cmd, rest) as conn:
File "C:\Python34\lib\ftplib.py", line 398, in transfercmd
return self.ntransfercmd(cmd, rest)[0]
File "C:\Python34\lib\ftplib.py", line 364, in ntransfercmd
resp = self.sendcmd(cmd)
File "C:\Python34\lib\ftplib.py", line 272, in sendcmd
return self.getresp()
File "C:\Python34\lib\ftplib.py", line 245, in getresp
raise error_perm(resp)
ftplib.error_perm: 500 ?
知道导致错误的原因吗？
如果响应的状态代码以“5”开头，ftplib 会引发错误。这意味着服务器正在返回 5xx 错误：
0.5.1 500 Internal Server Error
The server encountered an unexpected condition which prevented it from
fulfilling the request.
10.5.2 501 Not Implemented
The server does not support the functionality required to fulfill the
request. This is the appropriate response when the server does not
recognize the request method and is not capable of supporting it for
any resource.
10.5.3 502 Bad Gateway
The server, while acting as a gateway or proxy, received an invalid
response from the upstream server it accessed in attempting to fulfill
the request.
10.5.4 503 Service Unavailable
The server is currently unable to handle the request due to a
temporary overloading or maintenance of the server. The implication is
that this is a temporary condition which will be alleviated after some
delay. If known, the length of the delay MAY be indicated in a
Retry-After header. If no Retry-After is given, the client SHOULD
handle the response as it would for a 500 response.
Note: The existence of the 503 status code does not imply that a
server must use it when becoming overloaded. Some servers may wish
to simply refuse the connection.
10.5.5 504 Gateway Timeout
The server, while acting as a gateway or proxy, did not receive a
timely response from the upstream server specified by the URI (e.g.
HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
to access in attempting to complete the request.
Note: Note to implementors: some deployed proxies are known to
return 400 or 500 when DNS lookups time out.
10.5.6 505 HTTP Version Not Supported
The server does not support, or refuses to support, the HTTP protocol
version that was used in the request message. The server is indicating
that it is unable or unwilling to complete the request using the same
major version as the client, as described in section 3.1, other than
with this error message. The response SHOULD contain an entity
describing why that version is not supported and what other protocols
are supported by that server.
根据 ftp docs:
FTP.retrbinary(command, callback[, maxblocksize[, rest]])
Retrieve a
file in binary transfer mode. command should be an appropriate RETR
command: 'RETR filename'.
但是你写了这个：
ftp.retrbinary('RETR' + filename, localfile.write, 1024)
这将产生如下内容：
ftp.retrbinary('RETRdog.jpg', localfile.write, 1024)
您需要在'RETR'之后添加一个space。
使用 python
创建您自己的 ftp 服务器
顺便说一下，您可以编写一个简短的 python 程序来充当 ftp 服务器。首先安装模块 pyftpdlib:
$ pip3.4 install pyftpdlib #See note on 3.4 below
如果你的系统上只有一个版本的python，你可以只写：
$ pip install pyftpdlib
如果您的计算机上有多个版本的 python，请用正确的版本号替换 3.4。您指定的版本号是 pyftpdlib 模块将安装的 python 版本。
这是 ftp 服务器在 python 中的样子：
from pyftpdlib.authorizers import DummyAuthorizer
from pyftpdlib.handlers import FTPHandler
from pyftpdlib.servers import FTPServer
my_authorizer = DummyAuthorizer()
my_authorizer.add_user(
username = '7stud',
password = '1234',
homedir = '.',
perm='elrw' #permissions: 'e'->change dir, 'l'->list files, 'r'->retrieve files, 'w'->store a file to the server
)
my_handler = FTPHandler
my_handler.authorizer = my_authorizer
port = 2121
my_handler.banner = "You connected to my ftp server on port: {}".format(port)
address = ('localhost', port)
server = FTPServer(address, my_handler)
server.max_cons = 256
server.max_cons_per_ip = 5
server.serve_forever()
pyftpdlib 文档和教程 here。
add_user() 和权限描述 here。
然后，您可以为您的服务器创建一个目录：
$ mkdir ftp_server
$ cd ftp_server
$ touch my_ftp_server.py
将上面的代码放入文件my_ftp_server.py。然后在ftp_server目录下添加一些你要练习'downloading'的文件。然后通过运行ningmy_ftp_server.py.
启动服务器
在另一个终端 window 中，将目录切换到包含您的 python 程序的目录：
$ cd python_programs
然后对您的 ftp 客户端程序做一些小改动：
from ftplib import FTP
def getfile(conn): #It's good practice not to refer to global variables in your functions.
#Instead, pass in any values your function needs as arguments.
conn.retrlines('LIST') # List directory contents
filename = input('Name of file: ')
localfile = open(filename, 'wb')
ftp_command = 'RETR {}'.format(filename)
conn.retrbinary(ftp_command, localfile.write, 1024)
localfile.close()
user = '7stud'
passw = '1234'
port = 2121
url = input('FTP url: ').lower().strip()
ftp = FTP()
ftp.connect(url, port)
ftp.login(user, passw)
getfile(ftp)
ftp.quit()
这是您的 ftp 客户端程序的示例 运行：
~/python_programs$ python3.4 ftp_client.py
FTP url: localhost
drwxr-xr-x 4 7stud staff 136 Feb 11 09:07 cgi-bin
-rw-r--r-- 1 7stud staff 3446 Jun 08 2013 client_socket.py
-rw-r--r-- 1 7stud staff 680 Feb 15 03:03 ftp_server.py
-rw-r--r-- 1 7stud staff 721 Feb 12 03:01 http_server.py
-rw-r--r-- 1 7stud staff 498 Jan 01 07:10 index.html
-rw-r--r-- 1 7stud staff 68 Jan 01 05:03 oneliner.py
-rw-r--r-- 1 7stud staff 954 Feb 11 09:05 socket_server.py
-rw-r--r-- 1 7stud staff 0 Feb 15 02:50 test.png
Name of file: test.png
~/python_programs$ ls *.png
bar_freq.png example.png test.png
~/python_programs$
我正在使用 pythons ftplib 尝试从远程服务器检索文件（练习项目）。我在发送文件时没有遇到任何问题，但在尝试检索时遇到错误。我正在使用 python 3. 这是我的代码：
from ftplib import FTP
user = 'myusername'
passw = 'mypassw'
url = input('FTP url: ').lower().strip()
ftp = FTP(url) #connect to the host, default port
ftp.login(user, passw) # enters login info
def getfile():
ftp.retrlines('LIST') # List directory contents
filename = input('Name of file: ')
localfile = open(filename, 'wb')
ftp.retrbinary('RETR' + filename, localfile.write, 1024)
localfile.close()
getfile()
这是我得到的错误：
Traceback (most recent call last):
File "C:\Users\User\Desktop\School\python\ftpget.py", line 16, in <module>
getfile()
File "C:\Users\User\Desktop\School\python\ftpget.py", line 13, in getfile
ftp.retrbinary('RETR' + filename, localfile.write, 1024)
File "C:\Python34\lib\ftplib.py", line 441, in retrbinary
with self.transfercmd(cmd, rest) as conn:
File "C:\Python34\lib\ftplib.py", line 398, in transfercmd
return self.ntransfercmd(cmd, rest)[0]
File "C:\Python34\lib\ftplib.py", line 364, in ntransfercmd
resp = self.sendcmd(cmd)
File "C:\Python34\lib\ftplib.py", line 272, in sendcmd
return self.getresp()
File "C:\Python34\lib\ftplib.py", line 245, in getresp
raise error_perm(resp)
ftplib.error_perm: 500 ?
知道导致错误的原因吗？
ftplib 会引发错误。这意味着服务器正在返回 5xx 错误：
0.5.1 500 Internal Server Error
The server encountered an unexpected condition which prevented it from fulfilling the request.
10.5.2 501 Not Implemented
The server does not support the functionality required to fulfill the request. This is the appropriate response when the server does not recognize the request method and is not capable of supporting it for any resource.
10.5.3 502 Bad Gateway
The server, while acting as a gateway or proxy, received an invalid response from the upstream server it accessed in attempting to fulfill the request.
10.5.4 503 Service Unavailable
The server is currently unable to handle the request due to a temporary overloading or maintenance of the server. The implication is that this is a temporary condition which will be alleviated after some delay. If known, the length of the delay MAY be indicated in a Retry-After header. If no Retry-After is given, the client SHOULD handle the response as it would for a 500 response.
Note: The existence of the 503 status code does not imply that a server must use it when becoming overloaded. Some servers may wish to simply refuse the connection.10.5.5 504 Gateway Timeout
The server, while acting as a gateway or proxy, did not receive a timely response from the upstream server specified by the URI (e.g. HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed to access in attempting to complete the request.
Note: Note to implementors: some deployed proxies are known to return 400 or 500 when DNS lookups time out.10.5.6 505 HTTP Version Not Supported
The server does not support, or refuses to support, the HTTP protocol version that was used in the request message. The server is indicating that it is unable or unwilling to complete the request using the same major version as the client, as described in section 3.1, other than with this error message. The response SHOULD contain an entity describing why that version is not supported and what other protocols are supported by that server.
根据 ftp docs:
FTP.retrbinary(command, callback[, maxblocksize[, rest]])
Retrieve a file in binary transfer mode. command should be an appropriate RETR command: 'RETR filename'.
但是你写了这个：
ftp.retrbinary('RETR' + filename, localfile.write, 1024)
这将产生如下内容：
ftp.retrbinary('RETRdog.jpg', localfile.write, 1024)
您需要在'RETR'之后添加一个space。
使用 python
创建您自己的 ftp 服务器顺便说一下，您可以编写一个简短的 python 程序来充当 ftp 服务器。首先安装模块 pyftpdlib:
$ pip3.4 install pyftpdlib #See note on 3.4 below
如果你的系统上只有一个版本的python，你可以只写：
$ pip install pyftpdlib
如果您的计算机上有多个版本的 python，请用正确的版本号替换 3.4。您指定的版本号是 pyftpdlib 模块将安装的 python 版本。
这是 ftp 服务器在 python 中的样子：
from pyftpdlib.authorizers import DummyAuthorizer
from pyftpdlib.handlers import FTPHandler
from pyftpdlib.servers import FTPServer
my_authorizer = DummyAuthorizer()
my_authorizer.add_user(
username = '7stud',
password = '1234',
homedir = '.',
perm='elrw' #permissions: 'e'->change dir, 'l'->list files, 'r'->retrieve files, 'w'->store a file to the server
)
my_handler = FTPHandler
my_handler.authorizer = my_authorizer
port = 2121
my_handler.banner = "You connected to my ftp server on port: {}".format(port)
address = ('localhost', port)
server = FTPServer(address, my_handler)
server.max_cons = 256
server.max_cons_per_ip = 5
server.serve_forever()
pyftpdlib 文档和教程 here。
add_user() 和权限描述 here。
然后，您可以为您的服务器创建一个目录：
$ mkdir ftp_server
$ cd ftp_server
$ touch my_ftp_server.py
将上面的代码放入文件my_ftp_server.py。然后在ftp_server目录下添加一些你要练习'downloading'的文件。然后通过运行ningmy_ftp_server.py.
在另一个终端 window 中，将目录切换到包含您的 python 程序的目录：
$ cd python_programs
然后对您的 ftp 客户端程序做一些小改动：
from ftplib import FTP
def getfile(conn): #It's good practice not to refer to global variables in your functions.
#Instead, pass in any values your function needs as arguments.
conn.retrlines('LIST') # List directory contents
filename = input('Name of file: ')
localfile = open(filename, 'wb')
ftp_command = 'RETR {}'.format(filename)
conn.retrbinary(ftp_command, localfile.write, 1024)
localfile.close()
user = '7stud'
passw = '1234'
port = 2121
url = input('FTP url: ').lower().strip()
ftp = FTP()
ftp.connect(url, port)
ftp.login(user, passw)
getfile(ftp)
ftp.quit()
这是您的 ftp 客户端程序的示例 运行：
~/python_programs$ python3.4 ftp_client.py
FTP url: localhost
drwxr-xr-x 4 7stud staff 136 Feb 11 09:07 cgi-bin
-rw-r--r-- 1 7stud staff 3446 Jun 08 2013 client_socket.py
-rw-r--r-- 1 7stud staff 680 Feb 15 03:03 ftp_server.py
-rw-r--r-- 1 7stud staff 721 Feb 12 03:01 http_server.py
-rw-r--r-- 1 7stud staff 498 Jan 01 07:10 index.html
-rw-r--r-- 1 7stud staff 68 Jan 01 05:03 oneliner.py
-rw-r--r-- 1 7stud staff 954 Feb 11 09:05 socket_server.py
-rw-r--r-- 1 7stud staff 0 Feb 15 02:50 test.png
Name of file: test.png
~/python_programs$ ls *.png
bar_freq.png example.png test.png
~/python_programs$