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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