UDP-clients-server

This project was created to fulfill Ichiro's third internship assignment - Group Chat using clients-server (UDP implementation)

UDP Implementation - Group Chat

General Explanation

What is UDP?

UDP or User Datagram Protocol is connection-less protocol which is suitable for applications that require efficient communication that doesn't have to worry about packet loss. 

How does UDP work?

It sends packets (units of data transmission) directly to a target computer, without establishing a connection first, indicating the order of said packets, or checking whether they arrived as intended (UDP packets are referred to as ‘datagrams’).

This program, Group Chat, uses UDP for data transfer between clients and server. Some clients (more than 1) can send message to others and receive messgae from others. This program also uses broadcast message which is sent from server to all clients. The program also uses threading, so it can input message and send message to server simultaneously.

Documentation

Server Code

Use library socket, sys, and threading.

import socket
import sys
import threading

Declare ip address and port. This program uses local host ip address with port 2410.

UDP_IP_ADDRESS = '127.0.0.1'
UDP_PORT_NO = 2410

Create a socket with arguments socket.AF_INET (address family) and socket.SOCK_DGRAM (represent UDP).

serverSock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

Bind the socket to address with argument tuple: ip address and port.

serverSock.bind((UDP_IP_ADDRESS, UDP_PORT_NO))

Allows sockets to bind() to the same IP:port, with arguments socket.SOL_SOCKET as level, socket.SO_REUSEPORT as optname, and value = 1.

clientSock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)

Allows broadcast UDP packets to be sent and received, with arguments socket.SOL_SOCKET as level, socket.SO_BROADCAST as optname, and value = 1.

clientSock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)

Print additional message.

print("\n!!!Server is ready!!!")
print("\nYour chats will be recorded here")

Handle message receiving.

while True:
    # receive message from clients
    message, address = serverSock.recvfrom(1024)
    # use decode to convert bytes data type to string data type
    message_send = message.decode("utf-8")
    # print message
    print(message_send)
    # send broadcast message to all clients
    # use encode to convert string data to bytes data type
    serverSock.sendto(message_send.encode("utf-8"), ('<broadcast>', UDP_PORT_NO))

Clients Code

Use library socket, sys, and threading.

import socket
import sys
import threading

Function send_message() to send message to the server (as a target function in object Thread).

def send_message(clientSock):
    # input client's username as identity
    username = input("Input username: ")
    # input message and send it to the server
    while True:
        message = input()
        message_send = username + ': ' + message
        # use encode to convert string data to bytes data type
        clientSock.sendto(message_send.encode("utf-8"), (UDP_IP_ADDRESS, UDP_PORT_NO))
        # to delete message input
        sys.stdout.write("\033[F")

Declare ip address and port. This program uses ip address '0.0.0.0' and port 2410.

UDP_IP_ADDRESS = '0.0.0.0'
UDP_PORT_NO = 2410

Create a socket with arguments socket.AF_INET (address family) and socket.SOCK_DGRAM (represent UDP)

clientSock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

Allows sockets to bind() to the same IP:port, with arguments socket.SOL_SOCKET as level, socket.SO_REUSEPORT as optname, and value = 1.

clientSock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)

Allows broadcast UDP packets to be sent and received, with arguments socket.SOL_SOCKET as level, socket.SO_BROADCAST as optname, and value = 1.

clientSock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)

Bind the socket to address with argument tuple: ip address and port.

clientSock.bind((UDP_IP_ADDRESS, UDP_PORT_NO))

Print additional message.

print("\nWelcome to WhatsUDP Messenger!")

Create object Thread with target function send_message and argument function clientSock.

clientThread = threading.Thread(target=send_message, args=(clientSock,))
# start threading
clientThread.start()

Receive broadcast message from server and print it.

while True:
    data, addr = clientSock.recvfrom(1024)
    # use decode to convert bytes data type to string data type
    print(data.decode("utf-8"))

References

https://docs.python.org/3/library/socket.html

https://erlerobotics.gitbooks.io/erle-robotics-python-gitbook-free/content/udp_and_tcp/socket_options.html

https://tech.flipkart.com/linux-tcp-so-reuseport-usage-and-implementation-6bfbf642885a

https://www.cloudflare.com/learning/ddos/glossary/user-datagram-protocol-udp/