Notes

# importing the necessary modules.
import socket
import sys
import errno

# defining the header length.
HEADER_LENGTH = 10

# defining the IP address and Port Number.
IP = "10.20.101.28"
PORT = 3434

# Getting the name of the client.
my_username = input("Username: ")

"""
Creating a client socket and providing the address family (socket.AF_INET) and type of connection (socket.SOCK_STREAM), i.e. using TCP connection.
"""
client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

# Connecting the socket with the IP address and Port Number.
client_socket.connect((IP, PORT))

"""
Setting the connection to a non-blocking state so that the recv() function call will not get blocked. It will return some exceptions only.
"""
client_socket.setblocking(False)

# Setting the username and header.
username = my_username.encode('utf-8')
username_header = f"{len(username):<{HEADER_LENGTH}}".encode('utf-8')

"""
Here, we have encoded the username into bytes, counted the number of bytes, and then prepared a header of fixed size, that we have encoded to bytes as well.
"""

# sending the data.
client_socket.send(username_header + username)




# running an infinite loop to send continuous client requests.
while True:
# Getting user input.
message = input(f'{my_username} > ')

# Sending the non-empty message.
if message:
"""
encode the message into bytes, counted the number of bytes, and then prepared a header of fixed size, that we have encoded to bytes as well.
"""
message = message.encode('utf-8')
message_header = f"{len(message):<{HEADER_LENGTH}}".encode('utf-8')
# sending the message.
client_socket.send(message_header + message)

try:
# looping over the received messages and printing them.
while True:
# getting the header.
username_header = client_socket.recv(HEADER_LENGTH)

# If no header is accepted then finish the connection.
if not len(username_header):
print('Connection closed by the server')
sys.exit()

# Converting the header to an int value.
username_length = int(username_header.decode('utf-8').strip())

# Decoding the received username.
username = client_socket.recv(username_length).decode('utf-8')

# Decoding the received message.
message_header = client_socket.recv(HEADER_LENGTH)
message_length = int(message_header.decode('utf-8').strip())
message = client_socket.recv(message_length).decode('utf-8')

# Printing the message.
print(f'{username} > {message}')

except IOError as e:
# handling the normal error on nonblocking connections.
if e.errno != errno.EAGAIN and e.errno != errno.EWOULDBLOCK:
print('Reading error: {}'.format(str(e)))
sys.exit()

# If we did not receive anything, then continue.
continue

except Exception as e:
print('Reading error: '.format(str(e)))
sys.exit()