Python 中的 socket 模块
本文参考PYTHON 网络编程 第一章import socket
help(socket)
Functions:
socket() -- create a new socket object
socketpair() -- create a pair of new socket objects [*]
fromfd() -- create a socket object from an open file descriptor [*]
gethostname() -- return the current hostname
gethostbyname() -- map a hostname to its IP number
gethostbyaddr() -- map an IP number or hostname to DNS info
getservbyname() -- map a service name and a protocol name to a port number
getprotobyname() -- map a protocol name (e.g. 'tcp') to a number
ntohs(), ntohl() -- convert 16, 32 bit int from network to host byte order
htons(), htonl() -- convert 16, 32 bit int from host to network byte order
inet_aton() -- convert IP addr string (123.45.67.89) to 32-bit packed format
inet_ntoa() -- convert 32-bit packed format IP to string (123.45.67.89)
ssl() -- secure socket layer support (only available if configured)
socket.getdefaulttimeout() -- get the default timeout value
socket.setdefaulttimeout() -- set the default timeout value
create_connection() -- connects to an address, with an optional timeout and optional source address.
简单的介绍一下这些函数的作用：
一、socket类方法(直接可以通过socket 类进行调用)
1、gethostbyname() -- map a hostname to its IP number
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In : import socket
In : socket.gethostname()
Out: 'God'
2、gethostbyname() -- map a hostname to its IP number
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In : import socket
In : hostname=socket.gethostname()
In : print hostname
God
In : socket.gethostbyname(hostname)
Out: '127.0.1.1'
In : socket.gethostbyname('www.baidu.com')
Out: '119.75.218.70'
3、gethostbyaddr() -- map an IP number or hostname to DNS info
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In : import socket
In : socket.gethostbyaddr('God')
Out: ('God', [], ['127.0.1.1'])
In : socket.gethostbyaddr('119.75.218.70')
---------------------------------------------------------------------------
herror Traceback (most recent call last)
<ipython-input-14-612b876e1ed4> in <module>()
----> 1 socket.gethostbyaddr('119.75.218.70')
herror: Host name lookup failure
gethostbyname 和 gethostbyaddr 两个函数时要依赖于DNS的(首先会从/etc/hosts获取结果，然后在到dns服务器中获取相应结果)。
4、协议名 、端口号相关
getservbyport() --Return the service name from a port number and protocol name.
getservbyname() -- map a service name and a protocol name to a port number
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In : import socket
In : socket.getservbyname('http')
Out: 80
In : socket.getservbyport(21)
Out: 'ftp'
注释：getservbyport 和 getservbyname 两种方法获取的信息应该时从/etc/services 中获取
5、IPV4 地址转换
inet_aton() -- convert IP addr string (123.45.67.89) to 32-bit packed format
inet_ntoa() -- convert 32-bit packed format IP to string (123.45.67.89)
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In : add = '127.0.0.1'
In : packed_addr = socket.inet_aton(add)
In : addr2 = socket.inet_ntoa(packed_addr)
In : addr == addr2
Out: True
inet_ntop(...)
inet_ntop(af, packed_ip) -> string formatted IP address
Convert a packed IP address of the given family to string format.
inet_pton(...)
inet_pton(af, ip) -> packed IP address string
Convert an IP address from string format to a packed string suitable for use with low-level network functions.
通常会使用 inet_pton 去判断一个地址的有效性。例如判断一个IPV6地址是否有效
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def validip6addr(address):
"""
Returns True if `address` is a valid IPv6 address.
>>> validip6addr('::')
True
>>> validip6addr('aaaa:bbbb:cccc:dddd::1')
True
>>> validip6addr('1:2:3:4:5:6:7:8:9:10')
False
>>> validip6addr('12:10')
False
"""
try:
socket.inet_pton(socket.AF_INET6, address)
except (socket.error, AttributeError):
return False
return True
6、主机字节序和网络字节序之间相互转换(这种需要转换的数据仅仅限制于数字)
编写低层网络应用时,或许需要处理通过电缆在两台设备之间传送的低层数据。在这种操作中,需要把主机操作系统发出的数据转换成网络格式,或者做逆向转换,因为这两种数据的表示
方式不一样。(数据在电缆中的表示方式和在计算机中的表示方式是不一样的)
ntohs(), ntohl() -- convert 16, 32 bit int from network to host byte order
htons(), htonl() -- convert 16, 32 bit int from host to network byte order
注意：以上四个函数的参数全部都为数字，返回结构也全部都为数字
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In : data = 1234
In : print 'data:%s\nntohs:%s\nntohl:%s' %(data,socket.ntohs(data),socket.ntohl(data))
data:1234
ntohs:53764
ntohl:3523477504
In : print 'data:%s\nhtons:%s\nhtonl:%s' %(data,socket.htons(data),socket.htonl(data))
data:1234
htons:53764
htonl:3523477504
以上所有的函数都属于socket 类方法，直接通过socket 类即可调用
二、socket 实例调用
1、创建一个socket 实例
socket(]]) -> socket object
Open a socket of the given type.The family argument specifies the address family; it defaults to AF_INET.The type argument specifies
whether this is a stream (SOCK_STREAM, this is the default) or datagram (SOCK_DGRAM) socket.The protocol argument defaults to 0,
specifying the default protocol.Keyword arguments are accepted.
根据上面的英文解释：
family 默认值为 AF_INET 通常为默认即可
type 选择SOCK_STREAM(TCP) 和 SOCK_DGRAM(UDP) ,默认值为SOCK_STREAM
proto 默认为0 ，通常我们不用关系
建立一个tcp 的 socket 实例
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In : import socket
In : s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
OK,有了socket 实例，就可以使用很多socket 实例的方法了。这些方法有那些呢?
|Methods of socket objects (keyword arguments not allowed):
|
|accept() -- accept a connection, returning new socket and client address
|bind(addr) -- bind the socket to a local address
|close() -- close the socket
|connect(addr) -- connect the socket to a remote address
|connect_ex(addr) -- connect, return an error code instead of an exception
|dup() -- return a new socket object identical to the current one [*]
|fileno() -- return underlying file descriptor
|getpeername() -- return remote address [*]
|getsockname() -- return local address
|getsockopt(level, optname[, buflen]) -- get socket options
|gettimeout() -- return timeout or None
|listen(n) -- start listening for incoming connections
|makefile(]) -- return a file object for the socket [*]
|recv(buflen[, flags]) -- receive data
|recv_into(buffer[, nbytes[, flags]]) -- receive data (into a buffer)
|recvfrom(buflen[, flags]) -- receive data and sender's address
|recvfrom_into(buffer[, nbytes, [, flags])
| -- receive data and sender's address (into a buffer)
|sendall(data[, flags]) -- send all data
|send(data[, flags]) -- send data, may not send all of it
|sendto(data[, flags], addr) -- send data to a given address
|setblocking(0 | 1) -- set or clear the blocking I/O flag
|setsockopt(level, optname, value) -- set socket options
|settimeout(None | float) -- set or clear the timeout
|shutdown(how) -- shut down traffic in one or both directions
2、设定并获取默认的套接字超时时间
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In : import socket
In : s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
In : s.gettimeout()# 此时gettimeout 返回None,说明这个socket 没有设置超时处理
In : s.settimeout(60)
In : s.gettimeout()
Out: 60.0
3、修改、查看套接字属性 setsockopt 和 getsockopt
通过socket 实例 s获取 的帮助如下:
help(s.setsockopt)
setsockopt(...) method of socket._socketobject instance
setsockopt(level, option, value)
Set a socket option.See the Unix manual for level and option.The value argument can either be an integer or a string.
help(s.getsockopt)
getsockopt(...) method of socket._socketobject instance
getsockopt(level, option[, buffersize]) -> value
Get a socket option.See the Unix manual for level and option. If a nonzero buffersize argument is given, the return value is a string of that length; otherwise it is an integer.
其中 setsockopt 和getsockopt 中的 level、option 参数需要查看uninx 帮助手册去和获得相关信息
man 7 socket 可以看到相应的相关信息，其中有一段如下信息：
Socket options
The socket options listed below can be set by using setsockopt(2) and read with getsockopt(2) with the socket level set to SOL_SOCKET for all sock‐ets.Unless otherwise noted, optval is a pointer to an int.
介绍了 level 为 SOL_SOCKET 以及响应的option 字段信息
Example： 设置socket 发送和接收的缓冲区大小
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In : import socket
In : s = socket.socket(socket.AF_INET,socket.SOL_SOCKET)
In : s.getsockopt(socket.SOL_SOCKET,socket.SO_RCVBUF)
Out: 87380
In : s.getsockopt(socket.SOL_SOCKET,socket.SO_SNDBUF)
Out: 16384
In : s.setsockopt(socket.SOL_SOCKET,socket.SO_RCVBUF,4096)
In : s.getsockopt(socket.SOL_SOCKET,socket.SO_RCVBUF)
Out: 8192
In : s.setsockopt(socket.SOL_SOCKET,socket.SO_SNDBUF,4096)
In : s.getsockopt(socket.SOL_SOCKET,socket.SO_SNDBUF)
Out: 8192
4、把套接字改成阻塞或非阻塞模式
默认情况下,TCP套接字处于阻塞模式中。也就是说,除非完成了某项操作,否则不会把控制权交还给程序
通过socket 实例 s获取 的帮助如下:
setblocking(...) method of socket._socketobject instance
setblocking(flag)
Set the socket to blocking (flag is true) or non-blocking (false).
setblocking(True) is equivalent to settimeout(None);
setblocking(False) is equivalent to settimeout(0.0)
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In : s = socket.socket(socket.AF_INET,socket.SOL_SOCKET)
In : s.setblocking(True)
5、重用套接字地址
不管连接是被有意还是无意关闭,有时你想始终在同一个端口上运行套接字服务器。某些情
况下,如果客户端程序需要一直连接指定的服务器端口,这么做就很有用,因为无需改变服务器
端口
Example:
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#! /usr/bin/env python
# _*_ coding: utf-8 _*_
import socket
import sys
def reuse_socket_addr():
sock = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
old_state = sock.getsockopt(socket.SOL_SOCKET,socket.SO_REUSEADDR)
print "Old sock state: %s" %old_state
sock.setsockopt(socket.SOL_SOCKET,socket.SO_REUSEADDR,1)
new_state =sock.getsockopt(socket.SOL_SOCKET,socket.SO_REUSEADDR)
print "New sock state: %s" %new_state
local_port = 8282
srv = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
# 此时 socket 没有开启从用
srv.setsockopt(socket.SOL_SOCKET,socket.SO_REUSEADDR,0)
srv.bind(('',local_port))
srv.listen(1)
print "Listening on port: %s " %local_port
while True:
try:
conn, addr = srv.accept()
print "Connected by %s:%s" %(addr,addr)
except KeyboardInterrupt:
break
except socket.error,msg:
print '%s' %msg
if __name__ == "__main__":
reuse_socket_addr()
运行后在另一个终端对8282 端口进行重复的 telnet 操作，看看会出现什么效果
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$ python testsocketreuse.py
Old sock state: 0
New sock state: 1
Listening on port: 8282
Connected by 127.0.0.1:52733
退出后再次执行测试的 testsocketreuse.py 脚本
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Old sock state: 0
New sock state: 1
Traceback (most recent call last):
File "testsocketreuse.py", line 33, in <module>
reuse_socket_addr()
File "testsocketreuse.py", line 19, in reuse_socket_addr
srv.bind(('',local_port))
File "/usr/lib/python2.7/socket.py", line 224, in meth
return getattr(self._sock,name)(*args)
socket.error: Address already in use
此时发现端口已经被重用，无法再次执行，需要等待重用的端口资源释放后此可以执行成功。
启用端口重用：
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# 此时 socket 没有开启从用
srv.setsockopt(socket.SOL_SOCKET,socket.SO_REUSEADDR,1)
此时，再反复的执行此脚本，则没有发生端口重用的现象。
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