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Hi,

I want to make a UDP client server application that is conform to
RFC868 (Time protocol). Both the UDP client and UDP server are in a
test phase.

The question is: when I add "svrsocket.sendto(resultaat, (ip, port))"
in the UDP server, my application closes while running. When I leave
it away, it works fine. I really need this statement as the purpose is
that a client sends sth to the server and the server sends back the
time ticks.

Anybody an idea how I can modifu my client/server so that it works?

Regards,

Wim


Here is the server:

# UDP server example
import time
import socket
import string
import string

class Tijd:
def __init__(self, hours=0,minutes=0,seconds=0):
self.hours=hours
self.minutes=minutes
self.seconds=seconds

def aantal_seconden(self):
x = time.time()
y=(1970, 1, 1, 1, 0, 0, 0, 0, 0)
y=time.mktime(y)
resultaat=x-y
return resultaat

if __name__=="__main__":
tijd=Tijd()
resultaat=tijd.aantal_seconden()
print 'resultaat',resultaat

port=37

svrsocket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
svrsocket.bind(('', port))

hostname = socket.gethostname()
ip = socket.gethostbyname(hostname)
print 'TOD server is at IP adress: ', ip

tijd=time.ctime()
tijd=string.split(time.ctime())
print 'The current time is', tijd[3]
print 'Listening for TOD-requests on port %s ...' %port

while 1:
data, address = svrsocket.recvfrom(256)
print 'Received a TOD-request from modem with IP-address %s'
%address[0]
print 'Sending back the time to modem with
IP-address',address[0]
print "time", resultaat
svrsocket.sendto(resultaat, (ip, port))


And here is the client:

# UDP client example
import socket
port=37
clisocket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
while 1:
data = raw_input("Type something: ")
if data:
clisocket.sendto(data, ("127.0.0.1", port))
else:

break
s.close()

WIWA wrote:

> The question is: when I add "svrsocket.sendto(resultaat, (ip, port))"
> in the UDP server, my application closes while running. When I leave
> it away, it works fine. I really need this statement as the purpose is
> that a client sends sth to the server and the server sends back the
> time ticks.

It would have helped if you were more specific about: "closes while running"?
In my case (running your code) I get an exception in the server:


Traceback (most recent call last):
File "server.py", line 44, in ?
svrsocket.sendto(resultaat, (ip, port))
File "<string>", line 1, in sendto
TypeError: sendto() takes exactly 3 arguments (2 given)


this pretty much tells you what's wrong. Your sendto() call is faulty.

The first argument in your case is of type <float> while it should be
a <string>. So try

svrsocket.sendto(str(resultaat), (ip, port))

however, this triggers a loop in your code if your client is on the
same machine as the server (the server sends out a UDP packet to the
same port as it itself is listening on, on my machine, it gets back
its own UDP packet....)

HTH,
--Irmen de Jong

This should work:

Server
======

import socket
import time

# Constants.
PORT = 37

# Create and bind the socket which listens for packets.
srvsocket = socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
svrsocket.bind(('',PORT))

while 1:
# Block waiting for packet.
data, address = svrsocket.recvfrom(256)
print "Client sent:", data
print "Client at:", address
# Got a packet, reply to address packet came from.
srvsocket.sendto(str(time.time()),address)

Client
======

import socket

# Constants.
PORT = 37

# Create new socket, let it bind to an OS-chosen port.
clisocket = socket.socket(socket.AF_INET,socket.SOCK_DGRAM)

while 1:
data = raw_input("Enter what the server receives.")
if data:
# Send data to server, irrelevant what.
clisocket.sendto(data,("localhost",PORT))
# Block waiting for reply.
data, address = clisocket.recvfrom(256)
print "Server sent time:", data
else:
break

Look at the above code. There were several errors in your original
implementation, e.g. that time never got updated while the server ran,
and several other things. I also don't see the need for a Tijd class.

HTH!

Heiko.

PS: The above code is untested, if there's something wrong, my bad...
PPS: Read the UNIX TCP/IP Network Programming FAQ if you're into socket
programming! Google for it, I currently don't know the URL...