Python Sockets 连接到 FTP 没有收到我所期望的

Question

我正在使用 python 套接字连接到 ftp.reiris.es，但在发送数据后我没有收到我期望的答案。我用我的代码和答案更好地解释了这一点： 这是我的代码（test.py）

#!/usr/bin/env python

import socket

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

print "Socket Created"

port = 21

host = "ftp.rediris.es"

ip = socket.gethostbyname(host)

print ip

print "ip of " +host+ " is " +ip

s.connect ((ip, port))

print "Socket Connected to "+host+" on ip "+ ip

message = "HELP\r\n"

s.sendall(message)

reply = s.recv(65565)

print reply

这是我运行代码时的答案：

 python test.py
Socket Created
130.206.1.5
ip of ftp.rediris.es is 130.206.1.5
Socket Connected to ftp.rediris.es on ip 130.206.1.5
220-  Bienvenido al FTP anónimo de RedIRIS.
220-Welcome to the RedIRIS anonymous FTP server.
220 Only anonymous FTP is allowed here

这是我所期望的：

telnet
telnet> open ftp.rediris.es 21
Trying 130.206.1.5...
Connected to zeppo.rediris.es.
Escape character is '^]'.
220-  Bienvenido al FTP anónimo de RedIRIS.
220-Welcome to the RedIRIS anonymous FTP server.
220 Only anonymous FTP is allowed here
HELP
214-The following SITE commands are recognized
 ALIAS
 CHMOD
 IDLE
 UTIME

我已经在通往 www.google.com 的端口 80 上尝试过这个，发送一个 GET / HTTP/1.1\r\n\r\n 并且完美地看到了标题。 发生什么了？我没有将命令直接发送到服务器吗？提前谢谢你

Answer 1

您可以在发送HELP 消息之前检查是否已收到220 Only anonymous FTP is allowed here 的最后一行，例如telnetlib 中的read_until。

像这样，它对我有用：

import socket

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print "Socket Created"
port = 21
host = "ftp.rediris.es"
ip = socket.gethostbyname(host)

print ip
print "ip of " +host+ " is " +ip

s.connect ((ip, port))
print "Socket Connected to "+host+" on ip "+ ip

reply = ''
while True:
    message = "HELP\r\n"
    reply += s.recv(1024)
    if not reply:
        break
    if '220 Only anonymous FTP is allowed here' in reply:
        s.sendall(message)
        break    
reply += s.recv(65535)
print reply

打印输出：

Socket Created
130.206.1.5
ip of ftp.rediris.es is 130.206.1.5
Socket Connected to ftp.rediris.es on ip 130.206.1.5
220-  Bienvenido al FTP anónimo de RedIRIS.
220-Welcome to the RedIRIS anonymous FTP server.
220 Only anonymous FTP is allowed here
214-The following SITE commands are recognized
 ALIAS
 CHMOD
 IDLE
 UTIME
214 Pure-FTPd - http://pureftpd.org/

话虽如此，但不完全确定您为什么没有选择更合适的模块，例如 ftplib 或 telnetlib。