Python select.select模块通信全过程解析

# coding: utf-8
import select
import socket
import Queue
from time import sleep


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

# Bind the socket to the port
server_address = ('localhost', 8090)
print ('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
# 处理要发送的消息
outputs = []

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

while inputs:
 # Wait for at least one of the sockets to be ready for processing
 print ('waiting for the next event')
 # 开始select 监听, 对input_list 中的服务器端server 进行监听
 # 一旦调用socket的send, recv函数，将会再次调用此模块
 readable, writable, exceptional = select.select(inputs, outputs, inputs)

 # Handle inputs
 # 循环判断是否有客户端连接进来, 当有客户端连接进来时select 将触发
 for s in readable:
  # 判断当前触发的是不是服务端对象, 当触发的对象是服务端对象时,说明有新客户端连接进来了
  # 表示有新用户来连接
  if s is server:
   # A "readable" socket is ready to accept a connection
   connection, client_address = s.accept()
   print ('connection from', client_address)
   # this is connection not server
   connection.setblocking(0)
   # 将客户端对象也加入到监听的列表中, 当客户端发送消息时 select 将触发
   inputs.append(connection)

   # Give the connection a queue for data we want to send
   # 为连接的客户端单独创建一个消息队列，用来保存客户端发送的消息
   message_queues[connection] = Queue.Queue()
  else:
   # 有老用户发消息, 处理接受
   # 由于客户端连接进来时服务端接收客户端连接请求，将客户端加入到了监听列表中(input_list), 客户端发送消息将触发
   # 所以判断是否是客户端对象触发
   data = s.recv(1024)
   # 客户端未断开
   if data != '':
    # A readable client socket has data
    print ('received "%s" from %s' % (data, s.getpeername()))
    # 将收到的消息放入到相对应的socket客户端的消息队列中
    message_queues[s].put(data)
    # Add output channel for response
    # 将需要进行回复操作socket放到output 列表中, 让select监听
    if s not in outputs:
     outputs.append(s)
   else:
    # 客户端断开了连接, 将客户端的监听从input列表中移除
    # Interpret empty result as closed connection
    print ('closing', client_address)
    # Stop listening for input on the connection
    if s in outputs:
     outputs.remove(s)
    inputs.remove(s)
    s.close()

    # Remove message queue
    # 移除对应socket客户端对象的消息队列
    del message_queues[s]

 # Handle outputs
 # 如果现在没有客户端请求, 也没有客户端发送消息时, 开始对发送消息列表进行处理, 是否需要发送消息
 # 存储哪个客户端发送过消息
 for s in writable:
  try:
   # 如果消息队列中有消息,从消息队列中获取要发送的消息
   message_queue = message_queues.get(s)
   send_data = ''
   if message_queue is not None:
    send_data = message_queue.get_nowait()
   else:
    # 客户端连接断开了
    print "has closed "
  except Queue.Empty:
   # 客户端连接断开了
   print "%s" % (s.getpeername())
   outputs.remove(s)
  else:
   # print "sending %s to %s " % (send_data, s.getpeername)
   # print "send something"
   if message_queue is not None:
    s.send(send_data)
   else:
    print "has closed "
   # del message_queues[s]
   # writable.remove(s)
   # print "Client %s disconnected" % (client_address)

 # # Handle "exceptional conditions"
 # 处理异常的情况
 for s in exceptional:
  print ('exception condition on', s.getpeername())
  # Stop listening for input on the connection
  inputs.remove(s)
  if s in outputs:
   outputs.remove(s)
  s.close()

  # Remove message queue
  del message_queues[s]

 sleep(1)

# coding: utf-8
import socket


messages = ['This is the message ', 'It will be sent ', 'in parts ', ]

server_address = ('localhost', 8090)

# Create aTCP/IP socket

socks = [socket.socket(socket.AF_INET, socket.SOCK_STREAM), socket.socket(socket.AF_INET, socket.SOCK_STREAM), ]

# Connect thesocket to the port where the server is listening

print ('connecting to %s port %s' % server_address)
# 连接到服务器
for s in socks:
 s.connect(server_address)

for index, message in enumerate(messages):
 # Send messages on both sockets
 for s in socks:
  print ('%s: sending "%s"' % (s.getsockname(), message + str(index)))
  s.send(bytes(message + str(index)).decode('utf-8'))
 # Read responses on both sockets

for s in socks:
 data = s.recv(1024)
 print ('%s: received "%s"' % (s.getsockname(), data))
 if data != "":
  print ('closingsocket', s.getsockname())
  s.close()