1、Socket

socket起源于Unix,而Unix/Linux基本哲学之一就是“一切皆文件”,对于文件用【打开】【读写】【关闭】模式来操作。socket就是该模式的一个实现,socket即是一种特殊的文件,一些socket函数就是对其进行的操作(读/写IO、打开、关闭)

基本上,Socket 是任何一种计算机网络通讯中最基础的内容。例如当你在浏览器地址栏中输入 时,你会打开一个套接字,然后连接到 并读取响应的页面然后然后显示出来。而其他一些聊天客户端如 gtalk 和 skype 也是类似。任何网络通讯都是通过 Socket 来完成的。

Python 官方关于 Socket 的函数请看 http://docs.python.org/library/socket.html

2、Python提供了两个基本的socket模块

第一个是 Socket,它提供了标准的 BSD Sockets API。

第二个是 SocketServer, 它提供了服务器中心类,可以简化网络服务器的开发。

下面讲的是Socket模块功能

2.1 Socket 类型

套接字格式:

socket(family,type[,protocal]) 使用给定的地址族、套接字类型、协议编号(默认为0)来创建套接字。socket类型描述

socket.AF_UNIX只能够用于单一的Unix系统进程间通信

socket.AF_INET服务器之间网络通信

socket.AF_INET6IPv6

socket.SOCK_STREAM流式socket , for TCP

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_SEQPACKET可靠的连续数据包服务

创建TCP Socket:s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)

创建UDP Socket:s=socket.socket(socket.AF_INET,socket.SOCK_DGRAM)

2.2 Socket 函数

注意点:

1)TCP发送数据时,已建立好TCP连接,所以不需要指定地址。UDP是面向无连接的,每次发送要指定是发给谁。

2)服务端与客户端不能直接发送列表,元组,字典。需要字符串化repr(data)。socket函数描述

服务端socket函数

s.bind(address)将套接字绑定到地址, 在AF_INET下,以元组(host,port)的形式表示地址.

s.listen(backlog)开始监听TCP传入连接。backlog指定在拒绝连接之前,操作系统可以挂起的最大连接数量。该值至少为1,大部分应用程序设为5就可以了。

s.accept()接受TCP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。

客户端socket函数

s.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。

s.connect_ex(adddress)功能与connect(address)相同,但是成功返回0,失败返回errno的值。

公共socket函数

s.recv(bufsize[,flag])接受TCP套接字的数据。数据以字符串形式返回,bufsize指定要接收的最大数据量。flag提供有关消息的其他信息,通常可以忽略。

s.send(string[,flag])发送TCP数据。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。

s.sendall(string[,flag])完整发送TCP数据。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。

s.recvfrom(bufsize[.flag])接受UDP套接字的数据。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。

s.sendto(string[,flag],address)发送UDP数据。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。

s.close()关闭套接字。

s.getpeername()返回连接套接字的远程地址。返回值通常是元组(ipaddr,port)。

s.getsockname()返回套接字自己的地址。通常是一个元组(ipaddr,port)

s.setsockopt(level,optname,value)设置给定套接字选项的值。

s.getsockopt(level,optname[.buflen])返回套接字选项的值。

s.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connect())

s.gettimeout()返回当前超时期的值,单位是秒,如果没有设置超时期,则返回None。

s.fileno()返回套接字的文件描述符。

s.setblocking(flag)如果flag为0,则将套接字设为非阻塞模式,否则将套接字设为阻塞模式(默认值)。非阻塞模式下,如果调用recv()没有发现任何数据,或send()调用无法立即发送数据,那么将引起socket.error异常。

s.makefile()创建一个与该套接字相关连的文件

2.3 socket编程思路

TCP服务端:

(1)创建套接字,绑定套接字到本地IP与端口# socket.socket(socket.AF_INET,socket.SOCK_STREAM) , server.bind()

(2)开始监听连接# server.listen()

(3)进入循环,不断接受客户端的连接请求# server.accept()

(4)然后接收传来的数据,并发送给对方数据# server.recv() , server.sendall()

(5)传输完毕后,关闭套接字# server.close()

TCP客户端:

(1)创建套接字,连接远端地址# socket.socket(socket.AF_INET,socket.SOCK_STREAM) , client.connect()

(2)连接后发送数据和接收数据# client.sendall(), client.recv()

(3)传输完毕后,关闭套接字# client.close()

Socket编程之服务端代码:import socket # socket模块

import commands # 执行系统命令模块
HOST='127.0.0.1'
PORT=50007
server = socket.socket(socket.AF_INET,socket.SOCK_STREAM) # 定义socket类型,网络通信,TCP
server.bind((HOST,PORT)) # 套接字绑定的IP与端口
server.listen(1) # 开始TCP监听,1为最大等待连接数据
while True:
conn,addr=server.accept() # 接受TCP连接,并返回新的套接字与IP地址
print'Connected by',addr # 输出客户端的IP地址
while True:
data=conn.recv(1024) # 把接收的数据实例化
# commands.getstatusoutput执行系统命令(即shell命令),返回两个结果,第一个是状态,成功则为0,第二个是执行成功或失败的输出信息
cmd_status,cmd_result=commands.getstatusoutput(data)
# 如果输出结果长度为0,则告诉客户端完成。此用法针对于创建文件或目录,创建成功不会有输出信息
if len(cmd_result.strip()) ==0:
conn.sendall('Done.')
else:
conn.sendall(cmd_result) # 否则就把结果发给对端(即客户端)
conn.close() # 关闭连接
Socket编程之客户端代码:import socket
HOST='127.0.0.1'
PORT=50007
client=socket.socket(socket.AF_INET,socket.SOCK_STREAM) # 定义socket类型,网络通信,TCP
client.connect((HOST,PORT)) # 要连接的IP与端口
while 1:
cmd=raw_input("Please input cmd:") # 与人交互,输入命令
client.sendall(cmd) # 把命令发送给对端
data=client.recv(1024) # 把接收的数据定义为变量
print(data) # 输出变量
client.close() # 关闭连接

3、程序缺限

这是一个简单的socket通信,里面存在一些bug

问题1. 在客户端输入回车,会挂死。

问题2. 客户端断开后,服务器端会提示异常报错。

问题3. 服务端返回的数据大于1024,客户端显示不全,出现粘包问题。

问题4. 单进程,如果多个客户端连接,要排队,前一个断开,后一个客户端才能通信。

不想把代码写的太复杂,简单的说下解决方案:

问题1. 在客户端上判断输入为空,要求重新输入。

问题2. 添加异常处理

问题3. 在客户端上循环接收,直到接收完。但有没有完客户端是不知道的,需要服务端发一个结束符;或者是定制报头(比较好的方法)。

问题4. 在服务端导入SocketServer模块,使得每建立一个连接,就新创建一个线程。实现多个客户端与服务端通信。

后期会针对上面问题单独处理写出总结

4、I/O多路复用

I/O(input/output),即输入/输出端口。每个设备都会有一个专用的I/O地址,用来处理自己的输入输出信息首先什么是I/O?

I/O分为磁盘io和网络io,这里说的是网络io

IO多路复用:

I/O多路复用指:通过一种机制,可以监视多个描述符(socket),一旦某个描述符就绪(一般是读就绪或者写就绪),能够通知程序进行相应的读写操作。

Linux

Linux中的 select,poll,epoll 都是IO多路复用的机制。

Linux下网络I/O使用socket套接字来通信,普通I/O模型只能监听一个socket,而I/O多路复用可同时监听多个socket.

I/O多路复用避免阻塞在io上,原本为多进程或多线程来接收多个连接的消息变为单进程或单线程保存多个socket的状态后轮询处理.

Python

Python中有一个select模块,其中提供了:select、poll、epoll三个方法,分别调用系统的 select,poll,epoll 从而实现IO多路复用。Windows Python提供: select

Mac Python提供: select

Linux Python提供: select、poll、epoll

对于select模块操作的方法:

句柄列表11, 句柄列表22, 句柄列表33 = select.select(句柄序列1, 句柄序列2, 句柄序列3, 超时时间)

参数: 可接受四个参数(前三个必须)

返回值:三个列表

select方法用来监视文件句柄,如果句柄发生变化,则获取该句柄。

1. 当 参数1 序列中的句柄发生可读时(accetp和read),则获取发生变化的句柄并添加到 返回值1 序列中

2. 当 参数2 序列中含有句柄时,则将该序列中所有的句柄添加到 返回值2 序列中

3. 当 参数3 序列中的句柄发生错误时,则将该发生错误的句柄添加到 返回值3 序列中

4. 当 超时时间 未设置,则select会一直阻塞,直到监听的句柄发生变化

5. 当 超时时间 = 1时,那么如果监听的句柄均无任何变化,则select会阻塞 1 秒,之后返回三个空列表,如果监听的句柄有变化,则直接执行。import socket

import select
sk1 = socket.socket()
sk1.bind(("127.0.0.1",8001))
sk1.listen()
sk2 = socket.socket()
sk2.bind(("127.0.0.1",8002))
sk2.listen()
sk3 = socket.socket()
sk3.bind(("127.0.0.1",8003))
sk3.listen()
li = [sk1,sk2,sk3]
while True:
r_list,w_list,e_list = select.select(li,[],[],1) # r_list可变化的
for line in r_list:
conn,address = line.accept()
conn.sendall(bytes("Hello World !",encoding="utf-8"))
服务端sk1 = socket.socket()
sk1.bind(("127.0.0.1",8001))
sk1.listen()
inpu = [sk1,]
while True:
r_list,w_list,e_list = select.select(inpu,[],[],1)
for sk in r_list:
if sk == sk1:
conn,address = sk.accept()
inpu.append(conn)
else:
try:
ret = str(sk.recv(1024),encoding="utf-8")
sk.sendall(bytes(ret+"hao",encoding="utf-8"))
except Exception as ex:
inpu.remove(sk)
客户端import socket
obj = socket.socket()
obj.connect(('127.0.0.1',8001))
while True:
inp = input("Please(q\退出):\n>>>")
obj.sendall(bytes(inp,encoding="utf-8"))
if inp == "q":
break
ret = str(obj.recv(1024),encoding="utf-8")
print(ret)
服务端import socket
sk1 = socket.socket()
sk1.bind(("127.0.0.1",8001))
sk1.listen()
inputs = [sk1]
import select
message_dic = {}
outputs = []
while True:
r_list, w_list, e_list = select.select(inputs,[],inputs,1)
print("正在监听的socket对象%d" % len(inputs))
print(r_list)
for sk1_or_conn in r_list:
if sk1_or_conn == sk1:
conn,address = sk1_or_conn.accept()
inputs.append(conn)
message_dic[conn] = []
else:
try:
data_bytes = sk1_or_conn.recv(1024)
data_str = str(data_bytes,encoding="utf-8")
sk1_or_conn.sendall(bytes(data_str+"好",encoding="utf-8"))
except Exception as ex:
inputs.remove(sk1_or_conn)
else:
data_str = str(data_bytes,encoding="utf-8")
message_dic[sk1_or_conn].append(data_str)
outputs.append(sk1_or_conn)
for conn in w_list:
recv_str = message_dic[conn][0]
del message_dic[conn][0]
conn.sendall(bytes(recv_str+"好",encoding="utf-8"))
for sk in e_list:
inputs.remove(sk)
客户端import socket
obj = socket.socket()
obj.connect(('127.0.0.1',8001))
while True:
inp = input("Please(q\退出):\n>>>")
obj.sendall(bytes(inp,encoding="utf-8"))
if inp == "q":
break
ret = str(obj.recv(1024),encoding="utf-8")
print(ret)
5、socketserver

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服务端都会在服务器是创建一个“线程”或者“进程” 专门负责处理当前客户端的所有请求。

5.1 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。

ThreadingTCPServer基础

使用ThreadingTCPServer:创建一个继承自 SocketServer.BaseRequestHandler 的类

类中必须定义一个名称为 handle 的方法

启动ThreadingTCPServerimport socketserver

class Myserver(socketserver.BaseRequestHandler):
def handle(self):
conn = self.request
conn.sendall(bytes("你好,我是机器人",encoding="utf-8"))
while True:
ret_bytes = conn.recv(1024)
ret_str = str(ret_bytes,encoding="utf-8")
if ret_str == "q":
break
conn.sendall(bytes(ret_str+"你好我好大家好",encoding="utf-8"))
if __name__ == "__main__":
server = socketserver.ThreadingTCPServer(("127.0.0.1",8080),Myserver)
server.serve_forever()import socket
obj = socket.socket()
obj.connect(("127.0.0.1",8080))
ret_bytes = obj.recv(1024)
ret_str = str(ret_bytes,encoding="utf-8")
print(ret_str)
while True:
inp = input("你好请问您有什么问题? \n >>>")
if inp == "q":
obj.sendall(bytes(inp,encoding="utf-8"))
break
else:
obj.sendall(bytes(inp, encoding="utf-8"))
ret_bytes = obj.recv(1024)
ret_str = str(ret_bytes,encoding="utf-8")
print(ret_str)

2、ThreadingTCPServer源码剖析

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)

例如:

服务端import socketserver

class MyTcphandler(socketserver.BaseRequestHandler):
def handle(self):
print("建立的链接:",self.request)
print("客户端信息:%s:%s" % (self.client_address[0], self.client_address[1]))
while True: #通信循环
try:
client_data=self.request.recv(1024)
if not client_data: continue # 针对Linux的空
self.request.send(client_data.upper())
except Exception: # 针对Windows的空
break
if __name__ == '__main__':
#取代链接循环
server=socketserver.ThreadingTCPServer(('127.0.0.1',8080),MyTcphandler)
server.serve_forever()
客户端import socket
phone=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
phone.connect(('127.0.0.1',8080))
while True:
msg=input('>>: ').strip()
if not msg:continue
phone.send(msg.encode('utf-8'))
server_data=phone.recv(1024)
print(server_data.decode('utf-8'))
phone.close()
相对应的源码如下: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()
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

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)。