Python-来自服务器的UDP套接字检查响应

Question

I have a basic client/server program. The server sends a timestamp to the client. I want to check to see if the client has responded with message and if not, resend the request. How would I go about this?

while 1:
    wait = "True"

    line = raw_input("Press enter to get the time or \"STOP\" to exit: ")
    if line == "STOP":
            break
    print "Waiting for response......"
    s.sendto(line, (servAddr,servPort))
    line, server = s.recvfrom(256)
    while wait:         // Obviously wrong, but pseudo 
            if line == "":
                    print 'Send another'
                    wait = False

    print (line)

Answer 1

It seems you need either socket.settimeout() or select module.

With .settimeout() you can tell socket to raise socket.timeout exception if it didn't receive any data within the specified timeframe. This is good enough if your server only has to deal with one client (one client per thread/process/greenlet/whatever also works). If you want your server to do something while waiting for client to respond and you're not using any threading/asynchronous framework, you'll probably have to write a bit more code as you'll want to set zero timeout and track the time to re-send the message manually.

select module provides you with tools to listen to multiple sockets with a common timeout.