基于python select.select模块通信的实例讲解

readable, writable, exceptional = select.select(inputs, outputs, inputs)

# 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()