I am trying to implement a stop and wait algorithm. i have a problem in implementing the timeout at the sender. While waiting for an ACK from reciever, i am using the recvfrom() function. However this makes the program idle, and i can't follow the timeout to re transmit.
here is my code:
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()
                sockets block by default. Use the socket funcitons setblocking() or settimeout() to control this behavior.
if you want to do your own timing.
mysocket.setblocking(0)
ACK, address = mysocket.recvfrom(1024)
but I would do something like
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()
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