Python 中的 socket 模块

ewsd12

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 [1]: import socket In [2]: socket.gethostname() Out[2]: 'God'

2、gethostbyname() -- map a hostname to its IP number

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In [6]: import socket In [8]: hostname=socket.gethostname() In [9]: print hostname God In [10]: socket.gethostbyname(hostname) Out[10]: '127.0.1.1' In [11]: socket.gethostbyname('www.baidu.com') Out[11]: '119.75.218.70'

3、gethostbyaddr() -- map an IP number or hostname to DNS info

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In [12]: import socket In [13]: socket.gethostbyaddr('God') Out[13]: ('God', [], ['127.0.1.1']) In [14]: 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: [Errno 2] 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 [1]: import socket In [2]: socket.getservbyname('http') Out[2]: 80 In [4]: socket.getservbyport(21) Out[4]: '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 [20]: add = '127.0.0.1' In [21]: packed_addr = socket.inet_aton(add) In [23]: addr2 = socket.inet_ntoa(packed_addr) In [24]: addr == addr2 Out[24]: 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 [11]: data = 1234 In [19]: print 'data:%s\nntohs:%s\nntohl:%s' %(data,socket.ntohs(data),socket.ntohl(data)) data:1234 ntohs:53764 ntohl:3523477504 In [20]: 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([family[, type[, proto]]]) -> 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

1 2	In [6]: import socket In [7]: 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([mode, [bufsize]]) -- 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 [6]: import socket In [7]: s=socket.socket(socket.AF_INET,socket.SOCK_STREAM) In [9]: s.gettimeout()  # 此时gettimeout 返回None,说明这个socket 没有设置超时处理 In [10]: s.settimeout(60) In [11]: s.gettimeout() Out[11]: 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 [1]: import socket In [3]: s = socket.socket(socket.AF_INET,socket.SOL_SOCKET) In [4]: s.getsockopt(socket.SOL_SOCKET,socket.SO_RCVBUF) Out[4]: 87380 In [5]: s.getsockopt(socket.SOL_SOCKET,socket.SO_SNDBUF) Out[5]: 16384 In [6]: s.setsockopt(socket.SOL_SOCKET,socket.SO_RCVBUF,4096) In [7]: s.getsockopt(socket.SOL_SOCKET,socket.SO_RCVBUF) Out[7]: 8192 In [8]: s.setsockopt(socket.SOL_SOCKET,socket.SO_SNDBUF,4096) In [9]: s.getsockopt(socket.SOL_SOCKET,socket.SO_SNDBUF) Out[9]: 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)

1 2	In [2]: s = socket.socket(socket.AF_INET,socket.SOL_SOCKET) In [3]: 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[0],addr[1])         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: [Errno 98] 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：

1 2	# 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。