Python网络编程（一） 使用SocketServer.ForkingMixIn类的套接字服务器示例

实现方式是通过继承SocketServer.ForkingMixIn与SocketServer.TCPServer类，使用TCPServer类可以让套接字server端不需要手动实现创建套接字实例，绑定地址，进入监听模式等操作，继承ForkingMixIn类来处理异步客户端。

 

# socket test with ForkingMixIn class

import os
import socket
import SocketServer
import threading
# from multiprocessing import Process

SERVER_HOST = "localhost"
SERVER_PORT = 0 # indicat to use dyminic port
BUF_SIZE = 1024
ECHO_MSG = "Hello echo server"


class ForkingClient():
    """a client to use forking server """
    def __init__(self, ip, port):
        self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.sock.connect((ip, port))
    
    def run(self):
        """ client send infor to server """
        # get current client's ip 
        current_process_id = os.getpid()
        print "PID %s sending echo messages to server: %s" % \
            (current_process_id, ECHO_MSG)
        # use sock.send() to get length
        sent_data_length = self.sock.send(ECHO_MSG)
        print "%s characters sent so far..." % sent_data_length

        # get the server response
        s_response = self.sock.recv(BUF_SIZE)
        # disp the server response, split s_response
        print "PID %s received: %s" % ( current_process_id, s_response[5:] )

    def clientshutdown(self):
        self.sock.close()

# def server's handle mthd
class ForkingServerRequestHandler(SocketServer.BaseRequestHandler):
    def handle(self):
        # get echo from client, notice "request.recv()"
        data = self.request.recv(BUF_SIZE)
        current_process_id = os.getpid()
        s_response = '%s: %s' % ( current_process_id,  data)
        # send echo back to client
        print "Server sending back [current_process_id: data] %s" % \
            s_response
        # use .request.send() mthd
        self.request.send(s_response)
        # use return
        return

class ForkingServer(SocketServer.ForkingMixIn, SocketServer.TCPServer):
    """ just inherit everything from parents """
    pass

def main():
    # build the server like TCPServer initiate 
    server = ForkingServer( (SERVER_HOST, SERVER_PORT), ForkingServerRequestHandler)

    ip, port = server.server_address # get server's ip and port
    # serve_forever Handle requests until an explicit shutdown() request. 
    server_thread = threading.Thread(target=server.serve_forever)
    server_thread.setDaemon(True)

    # server start
    server_thread.start()
    #server_thread.join()
    print "Server loop runing PID: %s" % os.getpid()

    # build client and start

    client1 = ForkingClient(ip, port) # use server's ip and port
    client1.run()

    client2 = ForkingClient(ip, port)
    client2.run()

    # clean
    server.shutdown()
    client1.clientshutdown()
    client2.clientshutdown()
    server.socket.close()

if __name__ == '__main__':
    main()

 

注意点1：

初次在Windows上运行时报错如下， 在帮助文档查询到os.fork只能运行在unix平台：

报错如下：

File "C:\Python27\lib\SocketServer.py", line 556, in process_request:

pid = os.fork(）

AttributeError: 'module' object has no attribute 'fork'

os.fork()说明：  

Fork a child process. Return 0 in the child and the child’s process id in the parent. If an error occurs OSError is raised.Note that some platforms including FreeBSD <= 6.3, Cygwin and OS/2 EMX have known issues when using fork() from a thread.

Availability: Unix

注意点2：

在main块执行完SERVER和CLIENT的发送及接受后，SERVER执行了shutdown()后又执行socket.close()，为什么要这么做？

shutdown()关闭读写的连接并发送Fin/EOF 信号给所有的节点，而不管有多少进程连接在SERVER上，但是它不释放连接，所以再调用close()来释放