python网络编程——SocketServer/Twisted/paramiko模块

      在之前博客C/S架构的网络编程中，IO多路复用是将多个IO操作复用到1个服务端进程中进行处理，即无论有多少个客户端进行连接请求，服务端始终只有1个进程对客户端进行响应，这样的好处是节省了系统开销(select不适合单个客户端长会话操作，这样其它客户端连接请求就会一直等待，poll/epoll对select进行了改进)。下面介绍结合了IO多路复用和多进程(多线程)的SocketServer模块。

1 SocketServer模块

    SocketServer内部使用IO多路复用以及“多线程”和“多进程” ，从而实现并发处理多个客户端请求的Socket服务端。即：每个客户端请求连接到服务器时，Socket服务端都会创建一个“线程”或者“进程”专门负责处理当前客户端的所有请求。

    SocketServer与select/poll/epoll的本质区别：客户端第1次连接时，服务端就为该客户端创建一个线程或进程，此后服务端就利用此线程或进程与客户端进行通信，后续的数据传输几乎不要server端的直接参与。如果服务端创建的是进程，那么client1和client2同时向server端传输数据时是互不影响的；如果服务端创建的是线程(python中多线程，在同一时间只有一个线程在运行，底层会自动进行上下文切换，即python中不存在真正的多线程),那么client1和client2交替上传数据。

    知识回顾： python中的多线程，有一个GIL(全局解释器锁)限制在同一时刻只有1个线程在运行，底层自动进行上下文切换，保证多个线程轮流运行(cpu切片)，也就是python中不存在真正的多线程问题，伪多线程，实际多个线程不能真正实现并发处理。

   中间处理过程如图所示

        1.1 ThreadingTCPServer

                 ThreadingTCPServer实现的Soket服务器内部会为每个client创建一个 “线程”，该线程用来和客户端进行交互。

        1、ThreadingTCPServer基础

         使用ThreadingTCPServer要求:

          (1)创建一个继承自SocketServer.BaseRequestHandler的类   

          (2)类中必须定义一个名称为 handle 的方法

          (3)启动ThreadingTCPServer

#!/usr/bin/env python
# -*- coding:utf-8 -*-

import SocketServer

class MyServer(SocketServer.BaseRequestHandler):

    def handle(self):
        # print self.request,self.client_address,self.server
        conn = self.request
        conn.sendall('欢迎致电 10086，请输入1xxx,0转人工服务.')
        Flag = True
        while Flag:
            data = conn.recv(1024)
            if data == 'exit':
                Flag = False
            elif data == '0':
                conn.sendall('通过可能会被录音.balabala一大推')
            else:
                conn.sendall('请重新输入.')


if __name__ == '__main__':
    server = SocketServer.ThreadingTCPServer(('127.0.0.1',8009),MyServer)
    server.serve_forever()

#!/usr/bin/env python
# -*- coding:utf-8 -*-

import socket

ip_port = ('127.0.0.1',8009)
sk = socket.socket()
sk.connect(ip_port)
sk.settimeout(5)

while True:
    data = sk.recv(1024)
    print 'receive:',data
    inp = raw_input('please input:')
    sk.sendall(inp)
    if inp == 'exit':
        break

sk.close()

                2、ThreadingTCPServer源码剖析

             ThreadingTCPServer的类图关系如下：

      注：实际上在类的继承时，子类会继承父类的方法，所以我们在分析类的继承关系时，直接把父类的方法放到子类中，这样就直观些，在python中还有1点要注意的是子类到底是继承哪个父类的方法，因为python中存在多继承。

    内部调用流程为

启动服务端程序
1、执行TCPServer.__init__ 方法，创建服务端Socket对象并绑定IP和端口
2、执行BaseServer.__init__ 方法，将自定义的继承自SocketServer.BaseRequestHandler的类MyRequestHandle赋值给self.RequestHandlerClass
3、执行BaseServer.server_forever方法，While 循环一直监听是否有客户端请求到达 ...

当客户端连接到达服务器
4、执行ThreadingMixIn.process_request方法，创建一个“线程”用来处理请求
5、执行ThreadingMixIn.process_request_thread方法
6、执行BaseServer.finish_request方法，执行self.RequestHandlerClass()，即执行自定义MyRequestHandler的构造方法
  （自动调用基类BaseRequestHandler的构造方法，在该构造方法中又会调用MyRequestHandler的handle方法）

ThreadingTCPServer相关源码

class BaseServer:

    """Base class for server classes.

    Methods for the caller:

    - __init__(server_address, RequestHandlerClass)
    - serve_forever(poll_interval=0.5)
    - shutdown()
    - handle_request()  # if you do not use serve_forever()
    - fileno() -> int   # for select()

    Methods that may be overridden:

    - server_bind()
    - server_activate()
    - get_request() -> request, client_address
    - handle_timeout()
    - verify_request(request, client_address)
    - server_close()
    - process_request(request, client_address)
    - shutdown_request(request)
    - close_request(request)
    - handle_error()

    Methods for derived classes:

    - finish_request(request, client_address)

    Class variables that may be overridden by derived classes or
    instances:

    - timeout
    - address_family
    - socket_type
    - allow_reuse_address

    Instance variables:

    - RequestHandlerClass
    - socket

    """

    timeout = None

    def __init__(self, server_address, RequestHandlerClass):
        """Constructor.  May be extended, do not override."""
        self.server_address = server_address
        self.RequestHandlerClass = RequestHandlerClass
        self.__is_shut_down = threading.Event()
        self.__shutdown_request = False

    def server_activate(self):
        """Called by constructor to activate the server.

        May be overridden.

        """
        pass

    def serve_forever(self, poll_interval=0.5):
        """Handle one request at a time until shutdown.

        Polls for shutdown every poll_interval seconds. Ignores
        self.timeout. If you need to do periodic tasks, do them in
        another thread.
        """
        self.__is_shut_down.clear()
        try:
            while not self.__shutdown_request:
                # XXX: Consider using another file descriptor or
                # connecting to the socket to wake this up instead of
                # polling. Polling reduces our responsiveness to a
                # shutdown request and wastes cpu at all other times.
                r, w, e = _eintr_retry(select.select, [self], [], [],
                                       poll_interval)
                if self in r:
                    self._handle_request_noblock()
        finally:
            self.__shutdown_request = False
            self.__is_shut_down.set()

    def shutdown(self):
        """Stops the serve_forever loop.

        Blocks until the loop has finished. This must be called while
        serve_forever() is running in another thread, or it will
        deadlock.
        """
        self.__shutdown_request = True
        self.__is_shut_down.wait()

    # The distinction between handling, getting, processing and
    # finishing a request is fairly arbitrary.  Remember:
    #
    # - handle_request() is the top-level call.  It calls
    #   select, get_request(), verify_request() and process_request()
    # - get_request() is different for stream or datagram sockets
    # - process_request() is the place that may fork a new process
    #   or create a new thread to finish the request
    # - finish_request() instantiates the request handler class;
    #   this constructor will handle the request all by itself

    def handle_request(self):
        """Handle one request, possibly blocking.

        Respects self.timeout.
        """
        # Support people who used socket.settimeout() to escape
        # handle_request before self.timeout was available.
        timeout = self.socket.gettimeout()
        if timeout is None:
            timeout = self.timeout
        elif self.timeout is not None:
            timeout = min(timeout, self.timeout)
        fd_sets = _eintr_retry(select.select, [self], [], [], timeout)
        if not fd_sets[0]:
            self.handle_timeout()
            return
        self._handle_request_noblock()

    def _handle_request_noblock(self):
        """Handle one request, without blocking.

        I assume that select.select has returned that the socket is
        readable before this function was called, so there should be
        no risk of blocking in get_request().
        """
        try:
            request, client_address = self.get_request()
        except socket.error:
            return
        if self.verify_request(request, client_address):
            try:
                self.process_request(request, client_address)
            except:
                self.handle_error(request, client_address)
                self.shutdown_request(request)

    def handle_timeout(self):
        """Called if no new request arrives within self.timeout.

        Overridden by ForkingMixIn.
        """
        pass

    def verify_request(self, request, client_address):
        """Verify the request.  May be overridden.

        Return True if we should proceed with this request.

        """
        return True

    def process_request(self, request, client_address):
        """Call finish_request.

        Overridden by ForkingMixIn and ThreadingMixIn.

        """
        self.finish_request(request, client_address)
        self.shutdown_request(request)

    def server_close(self):
        """Called to clean-up the server.

        May be overridden.

        """
        pass

    def finish_request(self, request, client_address):
        """Finish one request by instantiating RequestHandlerClass."""
        self.RequestHandlerClass(request, client_address, self)

    def shutdown_request(self, request):
        """Called to shutdown and close an individual request."""
        self.close_request(request)

    def close_request(self, request):
        """Called to clean up an individual request."""
        pass

    def handle_error(self, request, client_address):
        """Handle an error gracefully.  May be overridden.

        The default is to print a traceback and continue.

        """
        print '-'*40
        print 'Exception happened during processing of request from',
        print client_address
        import traceback
        traceback.print_exc() # XXX But this goes to stderr!
        print '-'*40

class TCPServer(BaseServer):

    """Base class for various socket-based server classes.

    Defaults to synchronous IP stream (i.e., TCP).

    Methods for the caller:

    - __init__(server_address, RequestHandlerClass, bind_and_activate=True)
    - serve_forever(poll_interval=0.5)
    - shutdown()
    - handle_request()  # if you don't use serve_forever()
    - fileno() -> int   # for select()

    Methods that may be overridden:

    - server_bind()
    - server_activate()
    - get_request() -> request, client_address
    - handle_timeout()
    - verify_request(request, client_address)
    - process_request(request, client_address)
    - shutdown_request(request)
    - close_request(request)
    - handle_error()

    Methods for derived classes:

    - finish_request(request, client_address)

    Class variables that may be overridden by derived classes or
    instances:

    - timeout
    - address_family
    - socket_type
    - request_queue_size (only for stream sockets)
    - allow_reuse_address

    Instance variables:

    - server_address
    - RequestHandlerClass
    - socket

    """

    address_family = socket.AF_INET

    socket_type = socket.SOCK_STREAM

    request_queue_size = 5

    allow_reuse_address = False

    def __init__(self, server_address, RequestHandlerClass, bind_and_activate=True):
        """Constructor.  May be extended, do not override."""
        BaseServer.__init__(self, server_address, RequestHandlerClass)
        self.socket = socket.socket(self.address_family,
                                    self.socket_type)
        if bind_and_activate:
            try:
                self.server_bind()
                self.server_activate()
            except:
                self.server_close()
                raise

    def server_bind(self):
        """Called by constructor to bind the socket.

        May be overridden.

        """
        if self.allow_reuse_address:
            self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        self.socket.bind(self.server_address)
        self.server_address = self.socket.getsockname()

    def server_activate(self):
        """Called by constructor to activate the server.

        May be overridden.

        """
        self.socket.listen(self.request_queue_size)

    def server_close(self):
        """Called to clean-up the server.

        May be overridden.

        """
        self.socket.close()

    def fileno(self):
        """Return socket file number.

        Interface required by select().

        """
        return self.socket.fileno()

    def get_request(self):
        """Get the request and client address from the socket.

        May be overridden.

        """
        return self.socket.accept()

    def shutdown_request(self, request):
        """Called to shutdown and close an individual request."""
        try:
            #explicitly shutdown.  socket.close() merely releases
            #the socket and waits for GC to perform the actual close.
            request.shutdown(socket.SHUT_WR)
        except socket.error:
            pass #some platforms may raise ENOTCONN here
        self.close_request(request)

    def close_request(self, request):
        """Called to clean up an individual request."""
        request.close()

class ThreadingMixIn:
    """Mix-in class to handle each request in a new thread."""

    # Decides how threads will act upon termination of the
    # main process
    daemon_threads = False

    def process_request_thread(self, request, client_address):
        """Same as in BaseServer but as a thread.

        In addition, exception handling is done here.

        """
        try:
            self.finish_request(request, client_address)
            self.shutdown_request(request)
        except:
            self.handle_error(request, client_address)
            self.shutdown_request(request)

    def process_request(self, request, client_address):
        """Start a new thread to process the request."""
        t = threading.Thread(target = self.process_request_thread,
                             args = (request, client_address))
        t.daemon = self.daemon_threads
        t.start()

复制代码

class ThreadingTCPServer(ThreadingMixIn, TCPServer): 
        pass

RequestHandler相关源码

class BaseRequestHandler:

    """Base class for request handler classes.

    This class is instantiated for each request to be handled.  The
    constructor sets the instance variables request, client_address
    and server, and then calls the handle() method.  To implement a
    specific service, all you need to do is to derive a class which
    defines a handle() method.

    The handle() method can find the request as self.request, the
    client address as self.client_address, and the server (in case it
    needs access to per-server information) as self.server.  Since a
    separate instance is created for each request, the handle() method
    can define arbitrary other instance variariables.

    """

    def __init__(self, request, client_address, server):
        self.request = request
        self.client_address = client_address
        self.server = server
        self.setup()
        try:
            self.handle()
        finally:
            self.finish()

    def setup(self):
        pass

    def handle(self):
        pass

    def finish(self):
        pass

源码精简

import socket
import threading
import select

def process(request, client_address):
    print request,client_address
    conn = request
    conn.sendall('欢迎致电 10086，请输入1xxx,0转人工服务.')
    flag = True
    while flag:
        data = conn.recv(1024)
        if data == 'exit':
            flag = False
        elif data == '0':
            conn.sendall('通过可能会被录音.balabala一大推')
        else:
            conn.sendall('请重新输入.')

sk = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sk.bind(('127.0.0.1',8002))
sk.listen(5)

while True:
    r, w, e = select.select([sk,],[],[],1)
    print 'looping'
    if sk in r:
        print 'get request'
        request, client_address = sk.accept()
        t = threading.Thread(target=process, args=(request, client_address))
        t.daemon = False
        t.start()

sk.close()

    从精简代码可以看出，SocketServer的ThreadingTCPServer之所以可以同时处理请求得益于select和Threading两个东西，其实本质上就是在服务器端为每一个客户端创建一个线程，用于后续的数据处理，当前线程用来处理对应客户端的请求，所以可以支持同时n个客户端链接（长连接）。

      1.2 ForkingTCPServer

    ForkingTCPServer与ThreadingTCPServer的使用和执行流程基本一致，只不过在内部分别为请求者建立“进程”和“线程”。

    基本使用：

#!/usr/bin/env python
# -*- coding:utf-8 -*-

import SocketServer

class MyServer(SocketServer.BaseRequestHandler):

    def handle(self):
        # print self.request,self.client_address,self.server
        conn = self.request
        conn.sendall('欢迎致电 10086，请输入1xxx,0转人工服务.')
        Flag = True
        while Flag:
            data = conn.recv(1024)
            if data == 'exit':
                Flag = False
            elif data == '0':
                conn.sendall('通过可能会被录音.balabala一大推')
            else:
                conn.sendall('请重新输入.')


if __name__ == '__main__':
    server = SocketServer.ForkingTCPServer(('127.0.0.1',8009),MyServer)
    server.serve_forever()

#!/usr/bin/env python
# -*- coding:utf-8 -*-

import socket

ip_port = ('127.0.0.1',8009)
sk = socket.socket()
sk.connect(ip_port)
sk.settimeout(5)

while True:
    data = sk.recv(1024)
    print 'receive:',data
    inp = raw_input('please input:')
    sk.sendall(inp)
    if inp == 'exit':
        break

sk.close()

    以上ForkingTCPServer只是将 ThreadingTCPServer 实例中的代码：

server = SocketServer.ThreadingTCPServer(('127.0.0.1',8009),MyRequestHandler)

变更为：

server = SocketServer.ForkingTCPServer(('127.0.0.1',8009),MyRequestHandler)

    SocketServer的ThreadingTCPServer之所以可以同时处理请求得益于select和os.fork两个东西，其实本质上就是在服务器端为每一个客户端创建一个进程，用于后续数据处理，当前新创建的进程用来处理对应客户端的请求，所以，可以支持同时n个客户端链接（长连接）。

源码剖析参考 ThreadingTCPServer

2 Twisted模块

    使用传统的BIO（Blocking IO/阻塞IO）进行网络编程时，进行网络IO读写时都会阻塞当前线程，如果实现一个TCP服务器，都需要对每个客户端连接开启一个线程，而很多线程可能都在傻傻的阻塞住等待读写数据，系统资源消耗大。

    Twisted是用Python实现的基于事件驱动的网络引擎框架，功能非常丰富，基本包括了常用的网络组件,例如：网络协议、线程、数据库管理、网络操作、电子邮件等。

      编程框架，即别人预先定义好的一个框架（一个项目），如.net某个web框架有25个class，从BeginRequest依次执行类里的process方法。程序员自定义一个类添加到框架里，应用程序则从上到下运行，就会执行自定义代码。框架只知道这个类的列表，不关心具体内容，从上到下执行，类似于一个执行链，C#里叫委托链。也就是把代码类放到这个列表中，委托这个框架替你执行。

    事件驱动（not event），把自定义代码注册到框架中，框架代替你执行。或者框架提供几个接口，让你插入数据（python无接口概念，只有事件驱动）。委托不能为空，事件可以为空。通俗来讲，所谓事件驱动，就是说程序就像是一个报警器(reactor)，时刻等待着外部事件(event)，诸如有人入侵等，一旦有事件发生，程序就会触发一些特定的操作(callback)，注入拨打报警电话等。

    简而言之，事件驱动分为二个部分：第一，注册事件；第二，触发事件。

    自定义事件驱动框架如下：

#!/usr/bin/env python
# -*- coding:utf-8 -*-

#event_drive.py

event_list = []

def run():
    for event in event_list:
        obj = event()
        obj.execute()

class BaseHandler(object):
    """
    用户必须继承该类，从而规范所有类的方法（类似于接口的功能）
    """
    def execute(self):
        raise Exception('you must overwrite execute')

      程序员使用该自定义事件驱动框架

#!/usr/bin/env python
# -*- coding:utf-8 -*-

from source import event_drive

class MyHandler(event_drive.BaseHandler):

    def execute(self):
        print 'event-drive execute MyHandler'

event_drive.event_list.append(MyHandler)
event_drive.run()

执行过程：

1 导入自定义框架event_drive
2 自定义类MyClass,这个类必须继承event_drive中的BaseHandler类
3 MyClass类中重载execute方法
4 注册事件到框架的委托链，把自定义的类MyClass加入到事件列表event_list中（下面的Twisted框架是创建对象后改一个字段为类名也是同样的目的）
5 执行run方法

事件驱动只不过是框架规定了执行顺序，程序员在使用框架时，可以向原执行顺序中注册“事件”，从而在框架执行时可以出发已注册 的“事件”。

    基于事件驱动Twisted模块的Socket

   (1)由于twisted是第三方模块，默认没有安装，需要先安装 

cd Twisted-15.5.0
python setup.py build   #编译
python setup.py install #安装
上述安装方法适用于windows和linux的命令行安装，实际上也可以直接执行python setup.py install
注意：twisted依赖于zope和win32api模块，需要先安装依赖。

  （2）实例

#!/usr/bin/env python
# -*- coding:utf-8 -*-
 
from twisted.internet import protocol
from twisted.internet import reactor
 
class Echo(protocol.Protocol):   #继承protocol.py中的Protocol类
    def dataReceived(self, data): 
        self.transport.write(data)  #将收到的内容直接发送回去
 
def main():
    factory = protocol.ServerFactory()  #实例化
    factory.protocol = Echo   #将自定义类传给对象
 
    reactor.listenTCP(8000,factory)   #将端口和实例化对象作为参数传给reactor
    reactor.run()
 
if __name__ == '__main__':
    main()

import socket

ip_port=('127.0.0.1',8000)
sk=socket.socket()
sk.connect(ip_port)
sk.settimeout(5)
 
while True:
    inp=raw_input("please input:")
    sk.sendall(inp)
    print sk.recv(1024)
 
sk.close()

   源码类图关系

     实例执行流程

运行服务端程序
    创建Protocol的派生类Echo
    创建ServerFactory对象，并将Echo类封装到其protocol字段中
    执行reactor的listenTCP方法，内部使用tcp.Port创建socket server对象，并将该对象添加到了reactor的set类型的字段_read 中
    执行reactor的run方法，内部执行while循环，并通过select来监视_read中文件描述符是否有变化，循环中...

客户端请求到达
    执行reactor的_doReadOrWrite方法，其内部通过反射调用tcp.Port类的doRead方法，内部accept客户端连接并创建Server对象实例（用于封装客户端socket信息）和创建Echo对象实例（用于处理请求），然后调用Echo对象实例的makeConnection方法，创建连接。
    执行tcp.Server类的doRead方法，读取数据，
    执行tcp.Server类的_dataReceived方法，如果读取数据内容为空（关闭链接），否则，出发Echo的dataReceived方法
    执行Echo的dataReceived方法

    从源码可以看出，上述实例本质上使用了事件驱动的方法 和 IO多路复用的机制来进行Socket的处理。

    Pycharm debug模式调试调用关系

    Twisted优点：

     1、使用基于事件驱动的编程模型，而不是多线程模型。

     2、跨平台：为主流操作系统平台暴露出的事件通知系统提供统一的接口。

     3、“内置电池”的能力：提供流行的应用层协议实现，因此Twisted马上就可为开发人员所用。

     4、符合RFC规范，已经通过健壮的测试套件证明了其一致性。

     5、能很容易的配合多个网络协议一起使用。

     6、可扩展。

       更多Twisted内容，请参考：

       http://www.cnblogs.com/c9com/archive/2013/01/05/2845552.html（Twisted reactor解剖）

       http://www.cnblogs.com/zhangjing0502/archive/2012/07/11/2586666.html（Twisted的网络通信模型）

       http://www.cnblogs.com/zhangjing0502/archive/2012/07/11/2586575.html(Python中reactor,factory,protocol)

       http://www.cnblogs.com/zhangjing0502/archive/2012/05/16/2504415.html(Twisted异步编程--Deferred)

       http://www.cnblogs.com/zhangjing0502/archive/2012/05/30/2526552.html（[Python-Twisted] Twisted入门之端口转发服务器）

       http://www.cnblogs.com/Rex7/p/4752581.html(跟踪 twisted 里deferred 的Callback)

3 paramiko模块

   linux运维中都需要对服务器进行配置，如果服务器数量较多，那么可以进行远程自动化批量操作。在python中的paramiko模块就是实现远程执行命令的模块。使用paramiko模块仅需要在本地安装相应的模块（pycrypto以及paramiko模块），对远程服务器没有配置要求，paramiko模块基于ssh协议，实现对远程服务器的相关操作，对于连接多台服务器，进行复杂的连接操作特别有帮助。

    3.1 paramiko安装

1 windows下的安装paramiko
(1)解压pycrypto-2.6.tar.gz源码到路径C:Python27Libsite-packages
(2)在windows控制台下进入目录pycrypto-2.6，依次执行python setup.py build和python setup.py install
   window是如果没有安装编译器，那么会报错，解决办法是安装VCForPython27.msi(Microsoft Visual C++ Compiler for Python 2.7)
   编译过程中会出现“Unable to find vcvarsall.bat”的错误，解决方法参考http://blog.csdn.net/donger_soft/article/details/44838109
   测试是否安装成功：在python命令行下输入:import pycrypto，检查是否报错
(3)解压paramiko-1.10.1.tar.gz源码到路径C:Python27Libsite-packages
(4)在windows控制台下进入目录paramiko-1.10.1，依次执行python setup.py build和python setup.py install
   测试是否安装成功：在python命令行下输入:import paramiko，检查是否报错

2 ubuntu下的安装paramiko
(1)先安装python-devel(前提是要安装编译器gcc)
(2)解压pycrypto-2.6.tar.gz源码,进入目录pycrypto-2.6，执行python setup.py build && python setup.py install
   测试是否安装成功：在python命令行下输入:import pycrypto，检查是否报错
(3)解压paramiko-1.10.1.tar.gz源码，进入目录paramiko-1.10.1，执行python setup.py build && python setup.py install
   测试是否安装成功：在python命令行下输入:import paramiko，检查是否报错

      3.2 paramiko使用

SSHClient方法

#!/usr/bin/env python
#-*- coding:utf-8 -*-

import paramiko

ssh = paramiko.SSHClient() #创建ssh对象
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy()) #允许连接不在know_hosts文件中的主机
ssh.connect(hostname='192.168.1.100',port=22,username='root',password='111111') #hostname='主机名'或'ip地址'
stdin,stdout,stderror = ssh.exec_command('df') #在远程服务器执行命令df

print stdout.read() #获取命令结果
print stderror.read() #如果命令执行错误，则返回标准错误输出
ssh.close() #关闭连接

#!/usr/bin/env python
#-*- coding:utf-8 -*-

import paramiko

transport = paramiko.Transport(('192.168.7.100',22)) #创建transport对象
transport.connect(username='root',password='nihao123!')#调用连接方法connect

ssh = paramiko.SSHClient() #创建ssh对象
ssh._transport = transport #把上面创建的transport对象赋值给ssh对象中的_transport字段

stdin,stdout,stderr = ssh.exec_command('ifconfig') #执行命令ifconfig

print stdout.read()
print stderr.read()

transport.close()

  在上述两个实例中，其实实例1中connect内部封装了Transport，即：
   ssh = paramiko.SSHClient()
       t = self._transport = Transport(sock, gss_kex=gss_kex, gss_deleg_creds=gss_deleg_creds)
  注意：在操作文件时只能用实例2的方法

SFTPClient方法

#!/usr/bin/env python
#-*- coding:utf-8 -*-

import paramiko

private_key = paramiko.RSAKey.from_private_key_file('/root/.ssh/id_rsa')

ssh = paramiko.SSHClient()  #创建ssh对象
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy()) #允许连接不在know_host文件中的的主机
ssh.connect(hostname='192.168.1.100',port=22,username='root',pkey=private_key) #连接服务器
stdin,stdout,stderr = ssh.exec_command('ifconfig') #执行命令
print stdout.read() #获取命令执行结果
ssh.close()

'''
如果是运维人员这里不需要看
1、首先创建一个公钥和私钥
ssh-keygen
2、复制id_rsa.pub至要被远程执行命令的机器，并把id_rsa.pub里的内容增加至authorized_keys文件中
如果authorized_keys文件不存在创建即可
'''

#!/usr/bin/env python
#-*- coding:utf-8 -*-

import paramiko

private_key = paramiko.RSAKey.from_private_key_file('/root/.ssh/id_rsa')

transport = paramiko.Transport(('192.168.1.100',22))
transport.connect(username='root',pkey=private_key) #连接

sftp = paramiko.SFTPClient.from_transport(transport)#创建SFTPClient对象

sftp.put('test.zip','/tmp/test.zip')     #将test.zip上传到目标机器的/tmp/目录下，并命名为test.zip
sftp.get('/tmp/messages.log','test.log') #下载目标服务器/tmp/messages.log 到本地，并命名为test.log

transport.close()

   在远程服务器执行命令时，其实时间主要消耗在建立连接上了。

自定义类的，在连接后进行相应的上传下载操作，这样就可以在一次连接中进行其它操作，避免频繁的创建连接，关闭连接，减少资源消耗

#!/usr/bin/env python
#-*- coding:utf-8 -*-

import paramiko
import uuid

class DownUpLoad(object):
    def __init__(self,ip,port,user,passwd):
        self.hostname = ip
        self.port = port
        self.username = user
        self.password = passwd
        
    def create_file(self):
        file_name = str(uuid.uuid4())  #uuid.uuid4()会生成一个文件UUID，当作文件名
        with open(file_name,'wb') as f:
            f.write('This is test file！')
            return file_name

    def run(self):
        self.connect()
        self.upload()
        self.rename()
        self.close()

    def connect(self): #连接方法
        transport = paramiko.Transport((self.hostname, self.port)) #创建一个连接对象
        transport.connect(username=self.username, password=self.password)#调用transport对象中的连接方法
        self.__transport = transport #把transport赋值给__transport

    def close(self): #关闭连接
        self.__transport.close()

    def upload(self): #上传文件方法
        file_name = self.create_file() #创建文件
        sftp = paramiko.SFTPClient.from_transport(self.__transport) #创建基于transport连接的SFTPClient
        sftp.put(file_name,'/tmp/test.txt') #上传文件

    def rename(self): #执行命名方法
        ssh = paramiko.SSHClient() #建立ssh对象
        ssh._transport = self.__transport #替换ssh_transport字段为self.__transport
        stdin,stdout,stderr = ssh.exec_command('mv /tmp/test1 /tmp/test2') #执行命令
        print stdout.read() #读取执行命令

if __name__ == '__main__':
    ha = DownUpLoad()
    ha.run()

参考资料：

      http://www.cnblogs.com/wupeiqi/articles/5095821.html

      http://www.cnblogs.com/wupeiqi/articles/5040823.html

      http://www.cnblogs.com/luotianshuai/p/5111587.html

      http://www.cnblogs.com/luotianshuai/p/5131053.html