Python異步Socket編程

異步網絡據說能極大的提高網絡server的連接速度,所以打算寫一個專題,來學習和了解異步網絡.因為Python有個非常出名的異步Lib:Twisted,所以就用Python來完成. 

OK,首先寫一個pythone socket的server段,對開放三個端口:10000,10001,10002.krondo的例子中是每個server綁定一個端口,測試的時候需要分別開3個shell,分別運行.這太麻煩了,就分別用三個Thread來運行這些services. 

import optparse
import os
import socket
import time
from threading import Thread
import StringIO

txt = '''1111
2222
3333
4444
'''

def server(listen_socket):
    while True:
        buf = StringIO.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()
                        break
                    sock.sendall(line)  # this is a blocking call
                    print 'send bytes to client:%s' % line
                    #sock.close()
                except socket.error:
                    sock.close()
                    break
                time.sleep(1)  #server和client連接后，server會故意每發送一個單詞后等待一秒鍾后再發送另一個單詞


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 = (str('127.0.0.1'), port)
        listen_socket.bind(addres)
        listen_socket.listen(5)
        print "start listen at:%s" % (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的話,CPU會被Python完全占用了
        pass

下面是一個client,沒有才用異步網絡,連接這個三個端口的server: 

import socket


if __name__ == '__main__':
    ports = [10000, 10001, 10002]
    for port in ports:
        address = (str('127.0.0.1'), port)
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        sock.connect(address)
        poem = ''
        while True:
            data = sock.recv(4)
            if not data:
                sock.close()
                break
            poem += data
        print poem

下面用異步的client來讀取，代碼如下： 

import datetime, errno, optparse, select, socket

def connect(port):
    """Connect to the given server and return a non-blocking socket."""
    address = (str('127.0.0.1'), port)
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect(address)
    sock.setblocking(0)
    return sock

def format_address(address):
    host, port = address
    return '%s:%s' % (host or '127.0.0.1', port)

if __name__ == '__main__':
    ports = [10000, 10001, 10002]
    start = datetime.datetime.now()

    sockets = map(connect, ports)
    poems = dict.fromkeys(sockets, '') # socket -> accumulated poem

    # socket -> task numbers
    sock2task = dict([(s, i + 1) for i, s in enumerate(sockets)])
    sockets = list(sockets) # make a copy

    while sockets:
        #運用select來確保那些可讀取的異步socket可以立即開始讀取IO
        #OS不停的搜索目前可以read的socket，有的話就返回rlist
        rlist, _, _ = select.select(sockets, [], [])
        for sock in rlist:
            data = ''
            while True:
                try:
                    new_data = sock.recv(1024)
                except socket.error, e:
                    if e.args[0] == errno.EWOULDBLOCK:
                        break
                    raise
                else:
                    if not new_data:
                        break
                    else:
                        print new_data
                        data += new_data

            task_num = sock2task[sock]
            if not data:
                sockets.remove(sock)
                sock.close()
                print 'Task %d finished' % task_num
            else:
                addr_fmt = format_address(sock.getpeername())
                msg = 'Task %d: got %d bytes of poetry from %s'
                print  msg % (task_num, len(data), addr_fmt)

            poems[sock] += data

    elapsed = datetime.datetime.now() - start
    print 'Got poems in %s' %  elapsed

結果只需要4秒就完成了讀取任務。效率是剛才同步socket的三倍。對客戶端的異步改造主要有兩點： 

• 同步模式下，客戶端分別創建socket；而在異步模式下，client開始就創建了所有的socket。
• 通過“sock.setblocking(0)”設置socket為異步模式。
• 通過Unix系統的select倆返回可讀取IO
• 最為核心的是26行和29行。尤其是29行的select操作返回待讀取socket的列表。