UDP Socket Programming in Python

# Import the socket module.
from socket import *

# Set the destination address (IP, Port).
# A DNS lookup is done automatically to get the IP from serverName.
serverName = ""
serverPort = 11111

# Create the client's socket, clientSocket.
# AF_INET : address family, indicates the underlying network uses IPv4.
# SOCK_DGRAM : means it's a UDP socket.
clientSocket = socket(AF_INET, SOCK_DGRAM)

# The user enters a message.
message = input('Input lowercase sentence:')

# Attach the destination address (serverName, serverPort) to the packet (message.encode()) and send it through clientSocket.
# The source address is also attached to the packet, but not explicitly in the code; the underlying OS does it automatically.
clientSocket.sendto(message.encode(), (serverName, serverPort))

# Wait to receive from the server.
# When a packet arrives at the socket from the internet, it's assigned to the variables below.
# modifiedMessage : gets the packet data.
# serverAddress : gets the packet's source address (the server address). We already know it so it's not needed, but Python provides it.
# 2048 : accepts a buffer of this size.
modifiedMessage, serverAddress = clientSocket.recvfrom(2048)

# The arrived message is printed.
print(modifiedMessage.decode())

# Close the socket.
clientSocket.close()

# The process ends.

from socket import *

serverPort = 11111
serverSocket = socket(AF_INET, SOCK_DGRAM)

# Assign an address to the socket.
serverSocket.bind(("", serverPort))

print("The server is ready to receive")

while True:
    message, clientAddress = serverSocket.recvfrom(2048)
    modifiedMessage = message.decode().upper()
    serverSocket.sendto(modifiedMessage.encode(), clientAddress)