user3335367 user3335367 - 1 month ago 24
Python Question

UDP Client/Server Socket in Python

I'm new to python and sockets and am trying to write an echoing client/server socket. I have written the server so that 30% of the packets are lost. I programmed my client to timeout after one second since the packet could be lost. However, whenever I run my client socket, my output is 100% REQUEST TIMED OUT. I'm assuming I'm getting this output because my server is never receiving the message. I've looked over my code multiple times and cannot figure out why I am constantly getting this output. Below is my code for my server and client sockets. Any help would be appreciated.

Server Socket:

# We will need the following module to generate randomized lost packets
import random
from socket import *

# Create a UDP socket
# Notice the use of SOCK_DGRAM for UDP packets
serverSocket = socket(AF_INET, SOCK_DGRAM)

# Assign IP address and port number to socket
serverSocket.bind(('', 12000))

while True:
# Generate random number in the range of 0 to 10
rand = random.randint(0, 10)

# Receive the client packet along with the address it is coming from
message, address = serverSocket.recvfrom(1024)

# Capitalize the message from the client
message = message.upper()

# If rand is less is than 4, we consider the packet lost and do notrespond
if rand < 4:
continue

# Otherwise, the server responds
serverSocket.sendto(message, address)


Client Socket:

import time
from socket import *

pings = 1

#Send ping 10 times
while pings < 11:

#Create a UDP socket
clientSocket = socket(AF_INET, SOCK_DGRAM)

#Set a timeout value of 1 second
clientSocket.settimeout(1)

#Ping to server
message = 'test'

addr = ("127.0.0.1", 12000)

#Send ping
start = time.time()
clientSocket.sendto(message, addr)

#If data is received back from server, print
try:
data, server = clientSocket.recvfrom(1024)
end = time.time()
elapsed = end - start
print data + " " + pings + " "+ elapsed

#If data is not received back from server, print it has timed out
except timeout:
print 'REQUEST TIMED OUT'

pings = pings - 1

bsa bsa
Answer

I tested your code, and it works as expected on my machine. Your issue might not be your code. It could be a firewall or something else blocking all the packets on the loopback interface (127.0.0.1). Depending on your operating system, try testing with a packet monitor like Wireshark.

Also, here are a few suggestions on how to improve your code to be more Pythonic:

Server

import random
from socket import *

serverSocket = socket(AF_INET, SOCK_DGRAM)
serverSocket.bind(('', 12000))

while True:
    rand = random.randint(0, 10)
    message, address = serverSocket.recvfrom(1024)
    message = message.upper()
    if rand >= 4:
        serverSocket.sendto(message, address) 

Client

import time
from socket import *

for pings in range(10):
    clientSocket = socket(AF_INET, SOCK_DGRAM)
    clientSocket.settimeout(1)
    message = 'test'
    addr = ("127.0.0.1", 12000)

    start = time.time()
    clientSocket.sendto(message, addr)
    try:
        data, server = clientSocket.recvfrom(1024)
        end = time.time()
        elapsed = end - start
        print '%s %d %d' % (data, pings, elapsed)
    except timeout:
        print 'REQUEST TIMED OUT'
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