Creating a log for UDP connection

Question

I have having a problem with one of my university projects. We are doing sockets and UDP at the moment. Anyway so we had to make a very simple program, server, client, password name verification. He wanted us to make a log of things, and I created a module with methods to write to a log file, this works fine. I have called it from different places and it always works. The only time it does not work is when called from the server.

import datetime

###Appends the message to the server log with the current date and time
def AddToLogServer(message):
    f = open('Log_Server', 'a')

    time = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
    f.write(time +" " + message +"\n")
    f.close()

###Appends the message to the client log with the current date and time
def AddToLogClient(message):
    f = open('Log_Client', 'a')

    time = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
    f.write(time +" " + message +"\n")
    f.close()

This is the log creations. Works fine.

import socket
import sys
import Passwords
import getpass
import Log
###Create a connectionless network socket.
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
###Maximum size data.
MAX = 65535
PORT = 1060

if sys.argv[1:] == ['server']:
    ###Set server ip
    ip = '127.0.0.1'
    try:
        s.bind((ip, PORT))
    except:
        ###If the server fails to start this error message and the server should end.
        print "There is an error, perhaps the ip is already being used."
        s.close()
        sys.exit(1)
    ###Add to the server log that the server has started.
    Log.AddToLogServer("The server is up with the ip " + ip)
    print 'Server is up and listening at', s.getsockname()
    ###Listen for a client to send data to the server.
    while True:
        data, address = s.recvfrom(MAX)
        Passwords.getPasswordsAndUsers()
        ###Compare the name inputted to the ones in the user list
        i = Passwords.findUser(data)
        ###Update client log
        Log.AddToLogServer(address[0] +  " Inputted the name " + data)
        s.sendto(str(i), address)
        data, address = s.recvfrom(MAX)
        t = Passwords.checkPassword(data,i)
        ###if the password matched the user print out the correct message and send a message to the client
        if t == 1:
            Log.AddToLogServer(address[0] +  " Inputted the correct password for that user")
            print address[0] + " Has successfully entered the correct User and Password"
            s.sendto("The name and password were correct", address)
        ###if the password did not match the user print out the correct message and send a message to the client
        else:
            Log.AddToLogServer(address[0] +  " Inputted an incorrect password for that user")
            print address[0] + " Has failed to provide the correct Password for the inputted User"
            s.sendto("The password did not match the name", address)


elif sys.argv[1:] == ['client']:
    ###Takes in the ip and name as inputs.
    serverIp = raw_input("Please enter the server ip : ");
    username = raw_input("Enter your first name please: ");
    ### Attempts to send to the server with the given ip
    try:
        s.sendto(username, (serverIp, PORT))
    except:
        ###If the send fails then an error is shown and it finishes the execution.
        print "There was a problem sending to the server"
        s.close()
        sys.exit(1)
    ###Attempt to relieve data from the server, if the client does not then write the appropriate message.
    try:
        data, address = s.recvfrom(MAX)
    except:
        print "There was a problem receiving from the server"

        s.close()
        sys.exit(1)
    data = int(data)
    ###If the data was -1, then the user did not exist and an error should be displayed. Otherwise ask for the
    ###Password and send it to the server.
    if data != -1:
        password = getpass.getpass("Enter your password please: ");
        try:
            s.sendto(password, ('127.0.0.1', PORT))
        except:
            print "There was a problem sending to the server"
            s.close()
            sys.exit(1)
    else:
        print "This first name was not recognised."
        sys.exit(1)
    ###Again try to relieve data from the server and print out the output.
    try:
        data, address = s.recvfrom(MAX)
        print data
        s.close()

    except:
         print "There was a problem receiving to the server"
         s.close()
         sys.exit(1)

Client server code, the log does not work when called from the server while it is up.

Answer 1

I have tried reproducing the problem, but the script for the server did not execute. On my machine sys.argv[1:] returned [] , so i modified this part of your script if sys.argv[1:] == ['server']: to if sys.argv[1:] == []: Please see the response i got. You should look into that part. if sys.argv[1:] == ['server']:

The server is up with the ip 127.0.0.1
Server is up and listening at ('127.0.0.1', 1060)