# -*- coding: cp936 -*-
'''''
建立一个python server，监听指定端口，
如果该端口被远程连接访问，则获取远程连接，然后接收数据，
并且做出相应反馈。
'''
if __name__=="__main__":
    import socket
  print "Server is starting"
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.bind(('localhost', 8001)) #配置soket，绑定IP地址和端口号
    sock.listen(5) #设置最大允许连接数，各连接和server的通信遵循FIFO原则
    print "Server is listenting port 8001, with max connection 5"
    while True: #循环轮询socket状态，等待访问
        connection,address = sock.accept()
        try:
            connection.settimeout(50)
            #获得一个连接，然后开始循环处理这个连接发送的信息
            '''''
            如果server要同时处理多个连接，则下面的语句块应该用多线程来处理，
            否则server就始终在下面这个while语句块里被第一个连接所占用，
            无法去扫描其他新连接了，但多线程会影响代码结构，所以记得在连接数大于1时
            下面的语句要改为多线程即可。
            '''
            while True:
                buf = connection.recv(1024)
                print "Get value " +buf
                if buf == '1':
                  print "send welcome"
                  connection.send('welcome to server!')
                elif buf!='0':
                  connection.send('please go out!')
                  print "send refuse"
                else:
                  print "close"
                  break #退出连接监听循环
        except socket.timeout: #如果建立连接后，该连接在设定的时间内无数据发来，则time out
             print 'time out'
        print "closing one connection" #当一个连接监听循环退出后，连接可以关掉
        connection.close()

if __name__=="__main__":
    import socket
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect(('localhost', 8001))
    import time
    flag = '1'
    while True:
        time.sleep(3)
        print 'send to server with value: '+ flag
        sock.send(flag)
        print sock.recv(1024)
        flag = (flag=='1') and '2' or '1' #change to another type of value each time
    sock.close()

C:\Users\YanBo>D:\server.py
Server is starting
Server is listenting port 8001, with max connection 5

C:\Users\YanBo>D:\client.py
send to server with value: 1
welcome to server!
send to server with value: 2
please go out!
send to server with value: 1
welcome to server!
send to server with value: 2
please go out!
.....

Get value 1
send welcome
Get value 2
send refuse
.....

$ lsof -i:8001

yanbo@yanbo-linux64-01:~$ lsof -i:8001
COMMAND PID USER  FD  TYPE DEVICE SIZE/OFF NODE NAME
python 2413 yanbo  3u IPv4 12907   0t0 TCP localhost:8001 (LISTEN)
python 2413 yanbo  4u IPv4 12910   0t0 TCP localhost:8001->localhost:38609 (ESTABLISHED)
python 2469 yanbo  3u IPv4 12222   0t0 TCP localhost:38609->localhost:8001 (ESTABLISHED)