停止和等待算法的Python实现

Question

我正在尝试实现一个停止和等待算法.我在发件人实施超时时遇到问题.在等待来自接收方的ACK时,我正在使用recvfrom()函数.然而,这使程序空闲,我无法按照超时重新传输.

这是我的代码:

import socket

import time

mysocket=socket.socket(socket.AF_INET,socket.SOCK_DGRAM)


while True:


   ACK= " "

    userIn=raw_input()
    if not userIn : break
    mysocket.sendto(userIn, ('127.0.0.01', 88))     
    ACK, address = mysocket.recvfrom(1024)    #the prog. is idle waiting for ACK
    future=time.time()+0.5   
    while True:
            if time.time() > future:
                    mysocket.sendto(userIn, ('127.0.0.01', 88))
                    future=time.time()+0.5
            if (ACK!=" "):
                    print ACK
                    break 
mysocket.close()

Answer 1

默认情况下，套接字会阻塞。使用套接字函数 setblocking() 或 settimeout() 来控制此行为。

如果你想自己安排时间。

mysocket.setblocking(0)
ACK, address = mysocket.recvfrom(1024)

但我会做类似的事情

import socket

mysocket = socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
mysocket.settimeout(0.5)
dest = ('127.0.0.01', 88)

user_input = raw_input()

while user_input:
    mysocket.sendto(user_input, dest)     
    acknowledged = False
    # spam dest until they acknowledge me (sounds like my kids)
    while not acknowledged:
        try:
            ACK, address = mysocket.recvfrom(1024)
            acknowledged = True
        except socket.timeout:
            mysocket.sendto(user_input, dest)
    print ACK
    user_input = raw_input()

mysocket.close()