基于python select.select模块通信的实例讲解_Python

要理解select.select模块其实主要就是要理解它的参数, 以及其三个返回值。

select()方法接收并监控3个通信列表，第一个是所有的输入的data,就是指外部发过来的数据，第2个是监控和接收所有要发出去的data(outgoing data),第3个监控错误信息在网上一直在找这个select.select的参数解释, 但实在是没有, 哎...自己硬着头皮分析了一下。

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

第一个参数就是服务器端的socket, 第二个是我们在运行过程中存储的客户端的socket, 第三个存储错误信息。

重点是在返回值, 第一个返回的是可读的list, 第二个存储的是可写的list, 第三个存储的是错误信息的list。

这个也不必深究, 看看代码自己分析下就能有大概理解。

网上所有关于select.select的代码都是差不多的, 但是有些不能运行, 或是不全。我自己重新写了一份能运行的程序, 做了很多注释, 好好看看就能搞懂

服务器端：

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

									# 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)

客户端：

									# 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()

写代码过程中遇到了两个问题, 一是如何判断客户端已经关闭了socket连接, 后来自己分析了下, 如果关闭了客户端socket, 那么此时服务器端接收到的data就是'', 加个这个判断。二是如果服务器端关闭了socket, 一旦在调用socket的相关方法都会报错, 不管socket是不是用不同的容器存储的(意思是说list_1存储了socket1, list_2存储了socket1, 我关闭了socket1, 两者都不能在调用这个socket了)

服务器端：

基于python select.select模块通信的实例讲解