异步select

server coding:

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

import select
import socket
import sys
import Queue

# Create a TCP/IP socket
server = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
server.setblocking(False)

# Bind the socket to the port
server_address = ('localhost',1000)
print >>sys.stderr, 'starting up on %s port %s'%server_address
server.bind(server_address)

# Listen for incoming connections
server.listen(5)

# Sockets from which we expect to read
inputs = [server]

# Sockets to which we expect to write
outputs = []

# Outgoing message queues (socket:Queue)
message_queues = {}

while True:
    # Wait for at least one of the sockets to be ready for processing
    print >>sys.stderr, '
waiting for the next event'
    #分别筛选出可接收消息的sockets、等待发送消息的sockets、和中途出错的sockets。
    #其中exceptional为了把所有可接收消息的sockets都遍历到，所以要从inputs列表中读取。
    readable, writable, exceptional = select.select(inputs,outputs,inputs)

    # Handle inputs
    for s in readable:
        #第一种情况，创建一个待接收消息的socket放入inputs
        if s is server:
            # A "readable" server socket is ready to accept a connection
            connection, client_address = s.accept()
            print >>sys.stderr, 'new connection from', client_address
            connection.setblocking(0)
            inputs.append(connection)
            
            # Give the connection a queue for data we want to send
            message_queues[connection] = Queue.Queue()
            
        #第二种情况，在后续循环中，已经添加到inputs中的sockets已经不是readable了，所以
        #要进行接收消息，消息存在message_queues中，并把该socket添加到outputs。
        else:
            data = s.recv(1024)
            if data:
                # A readable client socket has data
                print >>sys.stderr, 'receieved "%s" from %s'%(data.upper(),s.getpeername())
                message_queues[s].put(data)
                # Add output channel for response，添加到待发送消息列表
                if s not in outputs:
                    outputs.append(s)
        
            #第三种情况就是这个客户端已经断开了，
            #所以你再通过recv()接收到的数据就为空了，
            #所以这个时候你就可以把这个跟客户端的连接关闭了。
            else:
                print >>sys.stderr, 'closing',client_address,'after reading no data'
                if s in outputs:
                    outputs.remove(s)#既然客户端都断开了，我就不用再给它返回数据了，所以这时候如果这个客户端的连接对象还在outputs列表中，就把它删掉
                inputs.remove(s)#inputs中也删除掉
                s.close()#把这个连接关闭掉
                
                 # Remove message queue
                del message_queues[s]
    
    # Handle outputs
    for s2 in writable:
        try:
            next_msg = message_queues[s2].get_nowait()
        #没有消息了
        except Queue.Empty:
            # No messages waiting so stop checking for writability.
            print >>sys.stderr,'output queue for',s2.getpeername(),'is empty'
            outputs.remove(s2)
        #发送消息
        else:
            print >>sys.stderr, 'sending "%s" to %s'%(next_msg,s2.getpeername())
            s2.send(next_msg)
    
    # Handle "exceptional conditions"
    for s3 in exceptional:
        print >>sys.stderr, 'handling exceptional condition for ',s3.getpeername()
        # Stop listening for input on the connection
        inputs.remove(s3)
        if s3 in outputs:
            outputs.remove(s3)
        s3.close()
        
        #Remove message queue
        del message_queues[s3]

                
            

client coding

# -*- coding: utf-8 -*-
"""
Created on Sun Oct 23 14:49:20 2016

@author: fuzzier
"""

import sys
import socket

messages = ['This is the message.',
            'It will be sent',
            'in parts.'
            ]
server_address = ('localhost',1000)

# Create a TCP/IP socket，创建两个客户端
socks = [socket.socket(socket.AF_INET,socket.SOCK_STREAM),
         socket.socket(socket.AF_INET,socket.SOCK_STREAM)
         ]

# Connect the socket to the port where the server is listening
print >>sys.stderr, 'connecting to %s port %s'%server_address
for s in socks:
    s.connect(server_address)

for message in messages:
    
    # Send messages on both sockets
    for s2 in socks:
        print >>sys.stderr, '%s:sending "%s"'%(s2.getsockname(),message)
        s2.send(message)
    
    #Read responses on both sockets
    for s3 in socks:
        data = s3.recv(1024)
        print >>sys.stderr, '%s: received "%s"' % (s3.getsockname(), data.upper())
        if not data:
            print >>sys.stderr,'closing socket',s3.getsockname()
            s3.close()

原理图：

运行结果：