参考： http://www.cnblogs.com/snailrun/p/3805188.html

异步网络据说能极大的提高网络server的连接速度,所以打算写一个专题,来学习和了解异步网络.因为Python有个非常出名的异步Lib:Twisted,所以就用Python来完成. 

OK,首先写一个pythone socket的server段,对开放三个端口:10000,10001,10002.krondo的例子中是每个server绑定一个端口,测试的时候需要分别开3个shell,分别运行.这太麻烦了,就分别用三个Thread来运行这些services. 

import optparse
import os
import socket
import time
from threading import Thread
from io import StringIOtxt = '''1111
2222
3333
4444
'''# 服务端程序处理过程
def server(listen_socket):while True:buf = StringIO(txt)sock, addr = listen_socket.accept()print('Somebody at %s wants poetry!' %(addr,))while True:try:line = buf.readline().strip()if not line:sock.close()breaksock.sendall(line.encode('utf8')) # this is a blocking callprint('send bytes to client: %s' %line)except socket.error:sock.close()breaktime.sleep(0.5) # server每发送一个单词后等待一会sock.close()print('\n')# 同时开启三个服务端线程，分别在三个端口监听
# 服务端程序为阻塞方式，只能一次服务于一个客户端
def main():ports = [10000, 10001, 10002]for port in ports:listen_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)listen_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)addres = ('127.0.0.1', port)listen_socket.bind(addres)listen_socket.listen(5)print("start listen at: %d" %port)worker = Thread(target = server, args = [listen_socket])worker.setDaemon(True)worker.start()if __name__ == '__main__':main()while True:time.sleep(0.1) # 如果不sleep的话, CPU会被Python完全占用了

下面是一个client, 用阻塞方式，先后连接这个三个端口的server: 

from socket import *# 建立三个客户端，分别连接三个不同的服务端程序, 接收服务端传过来的数据并打印
# 这三个客户端是阻塞方式通信的
if __name__ == '__main__':ports = [10000, 10001, 10002]for port in ports:address = ('127.0.0.1', port)sock = socket(AF_INET, SOCK_STREAM)sock.connect(address)poem = ''while True:data = sock.recv(4)if not data:sock.close()breakpoem += data.decode('utf8')print(poem)sock.close()

下面用异步的client来读取，代码如下：

import datetime, errno, optparse, select, socketdef connect(port):"""Connect to the given server and return a non-blocking socket."""address = ('127.0.0.1', port)sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)sock.connect(address)sock.setblocking(0)		# 设置为非阻塞模式return sockdef format_address(address):host, port = addressreturn '%s:%s' % (host or '127.0.0.1', port)if __name__ == '__main__':ports = [10000, 10001, 10002]start = datetime.datetime.now()sockets = list(map(connect, ports))poems = dict.fromkeys(sockets, '') # socket -> accumulated poemsock2task = dict([(s, i + 1) for i, s in enumerate(sockets)])while sockets:#运用select来确保那些可读取的异步socket可以立即开始读取IO#OS不停的搜索目前可以read的socket，有的话就返回rlistrlist, _, _ = select.select(sockets, [], [])for sock in rlist:data = ''while True:try:new_data = sock.recv(1024)new_data = new_data.decode('utf8')except socket.error as e:if e.args[0] == errno.EWOULDBLOCK:breakraiseelse:if not new_data:breakelse:print(new_data)data += new_datatask_num = sock2task[sock]if not data:print(poems[sock])	# 打印sock接收到的数据sockets.remove(sock)sock.close()print('Task %d finished\n' % task_num)else:addr_fmt = format_address(sock.getpeername())msg = 'Task %d: got %d bytes of poetry from %s\n'print(msg % (task_num, len(data), addr_fmt))poems[sock] += data		# 保存每个sock接收到的数据elapsed = datetime.datetime.now() - startprint('Got poems in %s' %elapsed)

结果只需要2秒就完成了读取任务。效率非常明显啊。对客户端的异步改造主要有两点： 

• • 同步模式下，客户端分别创建socket；而在异步模式下，client开始就创建了所有的socket。
  • 通过“sock.setblocking(0)”设置socket为异步模式。
  • 通过Unix系统的select来返回可读取socket信息
  • 最为核心的是8行和26行。尤其是26行的select操作返回待读取socket的列表。