Stop-and-Wait算法的Python实现

Question

我正在尝试实现一个停止等待算法。我在发送者处执行超时时遇到问题。在等待recier的ACK时，我正在使用recvfrom（）函数。但是这使得程序空闲，我不能跟随超时来重新传输。

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，套接字块。使用套接字函数setblocking（）或settimeout（）来控制此行为。

如果你想做你自己的时机。

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

但我会做些

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()