Python自动化 【第八篇】:Python基础-Socket编程进阶
本节内容:
- Socket语法及相关
- SocketServer实现多并发
1. Socket语法及相关
sk = socket.socket(socket.AF_INET,socket.SOCK_STREAM,0)
参数一:地址簇
socket.AF_INET IPv4(默认)
socket.AF_INET6 IPv6
socket.AF_UNIX 只能够用于单一的Unix系统进程间通信
参数二:类型
socket.SOCK_STREAM 流式socket , for TCP (默认)
socket.SOCK_DGRAM 数据报式socket
, for UDP
socket.SOCK_RAW 原始套接字,普通的套接字无法处理ICMP、IGMP等网络报文,而SOCK_RAW可以;其次,SOCK_RAW也可以处理特殊的IPv4报文;此外,利用原始套接字,可以通过IP_HDRINCL套接字选项由用户构造IP头。
socket.SOCK_RDM 是一种可靠的UDP形式,即保证交付数据报但不保证顺序。SOCK_RAM用来提供对原始协议的低级访问,在需要执行某些特殊操作时使用,如发送ICMP报文。SOCK_RAM通常仅限于高级用户或管理员运行的程序使用。
socket.SOCK_SEQPACKET 可靠的连续数据包服务
参数三:协议
0 (默认)与特定的地址家族相关的协议,如果是 0 ,则系统就会根据地址格式和套接类别,自动选择一个合适的协议
- sk.bind(address) 将套接字绑定到地址。address地址的格式取决于地址族。在AF_INET下,以元组(host,port)的形式表示地址。
- sk.listen(backlog) 开始监听传入连接。backlog指定在拒绝连接之前,可以挂起的最大连接数量。backlog等于5,表示内核已经接到了连接请求,但服务器还没有调用accept进行处理的连接个数最大为5。这个值不能无限大,因为要在内核中维护连接队列。
- sk.setblocking(bool) 是否阻塞(默认True),如果设置False,那么accept和recv时一旦无数据,则报错。
- sk.accept() 接受连接并返回(conn,address),其中conn是新的套接字对象,可以用来接收和发送数据。address是连接客户端的地址。接收TCP 客户的连接(阻塞式)等待连接的到来。
- sk.connect(address) 连接到address处的套接字。一般,address的格式为元组(hostname,port),如果连接出错,返回socket.error错误。
- sk.connect_ex(address) 同上,只不过会有返回值,连接成功时返回 0 ,连接失败时候返回编码,例如:10061
- sk.close() 关闭套接字
- sk.recv(bufsize[,flag]) 接受套接字的数据。数据以字符串形式返回,bufsize指定最多可以接收的数量。flag提供有关消息的其他信息,通常可以忽略。
- sk.recvfrom(bufsize[.flag]) 与recv()类似,但返回值是(data,address)。其中data是包含接收数据的字符串,address是发送数据的套接字地址。
- sk.send(string[,flag]) 将string中的数据发送到连接的套接字。返回值是要发送的字节数量,该数量可能小于string的字节大小。即:可能未将指定内容全部发送。
- sk.sendall(string[,flag]) 将string中的数据发送到连接的套接字,但在返回之前会尝试发送所有数据。成功返回None,失败则抛出异常。内部通过递归调用send,将所有内容发送出去。
- sk.sendto(string[,flag],address) 将数据发送到套接字,address是形式为(ipaddr,port)的元组,指定远程地址。返回值是发送的字节数。该函数主要用于UDP协议。
- sk.settimeout(timeout) 设置套接字操作的超时期,timeout是一个浮点数,单位是秒。值为None表示没有超时期。一般,超时期应该在刚创建套接字时设置,因为它们可能用于连接的操作(如 client 连接最多等待5s )
- sk.getpeername() 返回连接套接字的远程地址。返回值通常是元组(ipaddr,port)。
- sk.getsockname() 返回套接字自己的地址。通常是一个元组(ipaddr,port)
- sk.fileno() 套接字的文件描述符
2. SocketServer实现多并发
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。
+------------+
| BaseServer |
+------------+
|
v
+-----------+ +------------------+
| TCPServer |------->| UnixStreamServer |
+-----------+ +------------------+
|
v
+-----------+ +--------------------+
| UDPServer |------->| UnixDatagramServer |
SocketServer简化了网络服务器的编写。它有4个类:TCPServer,UDPServer,UnixStreamServer,UnixDatagramServer。
这4个类是同步进行处理的,另外通过ForkingMixIn和ThreadingMixIn类来支持异步。
创建socketserver的步骤:
- 自己创建一个请求处理类,并且这个类要继承BaseRequestHandler,并且重写父类里的handle方法
- 必须实例化TCPserver,并且传递server ip和 你上面创建的请求处理类给这个TCPserver
- server.handle_request() #只处理一个请求 (不建议用); server.serve_forever() #处理多个请求 ,永远执行。
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:
- import SocketServer
- class MyTCPserver(SocketServer.BaseRequestHandler):
- def handle(self):
- pass
- if __name__ == '__main__':
- server = SocketServer.ThreadingTCPServer(('127.0.0.1',5566), MyTCPserver)
- server.serve_forever()
Threading TCP server
2)ThreadingTCPServer源码剖析
ThreadingTCPServer的类图关系如下:
内部调用流程为:
- 启动服务端程序
- 执行 TCPServer.__init__ 方法,创建服务端Socket对象并绑定 IP 和 端口
- 执行 BaseServer.__init__ 方法,将自定义的继承自SocketServer.BaseRequestHandler 的类 MyRequestHandle赋值给self.RequestHandlerClass
- 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
- 执行 ThreadingMixIn.process_request 方法,创建一个 “线程” 用来处理请求
- 执行 ThreadingMixIn.process_request_thread 方法
- 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:
BaseServer
- 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.
- """
- '-' * 40
- 'Exception happened during processing of request from',
- client_address
- import traceback
- traceback.print_exc() # XXX But this goes to stderr!
- '-' * 40
base server
TCPServer
- 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()
TCP server
ThreadingMixIn
- 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()
threading mix-in
ThreadingTCPServer
- class ThreadingTCPServer(ThreadingMixIn, TCPServer): pass
threading TCP server
RequestHandler相关源码:
- BaseRequestHandler
- 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
request handler
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,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)。
socketserver 实例:
server side:
- import socketserver
- class MyTCPHandler(socketserver.BaseRequestHandler):
- """
- The request handler class for our server.
- It is instantiated once per connection to the server, and must
- override the handle() method to implement communication to the
- client.
- """
- def handle(self):
- # self.request is the TCP socket connected to the client
- self.data = self.request.recv(1024).strip()
- print("{} wrote:".format(self.client_address[0]))
- print(self.data)
- # just send back the same data, but upper-cased
- self.request.sendall(self.data.upper())
- if __name__ == "__main__":
- HOST, PORT = "localhost", 9999
- # Create the server, binding to localhost on port 9999
- server = socketserver.ThreadingTCPServer((HOST, PORT), MyTCPHandler)
- # Activate the server; this will keep running until you
- # interrupt the program with Ctrl-C
- server.serve_forever()
server side
client side:
- import socket
- import sys
- HOST, PORT = "localhost", 9999
- data = " ".join(sys.argv[1:])
- # Create a socket (SOCK_STREAM means a TCP socket)
- sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
- try:
- # Connect to server and send data
- sock.connect((HOST, PORT))
- sock.sendall(bytes(data + "\n", "utf-8"))
- # Receive data from the server and shut down
- received = str(sock.recv(1024), "utf-8")
- finally:
- sock.close()
- print("Sent: {}".format(data))
- print("Received: {}".format(received))
client side
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