How to send file in python over network without loosing data?

I'm trying to send a file data.txt that contains this words 'hello world' over my network using 2 files in Python, one called server.py :

import socket
import tqdm
import os

# device's IP address
SERVER_HOST = "0.0.0.0"
SERVER_PORT = 5001
# receive 4096 bytes each time
BUFFER_SIZE = 4096
SEPARATOR = "<SEPARATOR>"

# create the server socket
# TCP socket
s = socket.socket()

# bind the socket to our local address
s.bind((SERVER_HOST, SERVER_PORT))

# enabling our server to accept connections
# 5 here is the number of unaccepted connections that
# the system will allow before refusing new connections
s.listen(5)
print(f"[*] Listening as {SERVER_HOST}:{SERVER_PORT}")

# accept connection if there is any
client_socket, address = s.accept() 
# if below code is executed, that means the sender is connected
print(f"[+] {address} is connected.")

# receive the file infos
# receive using client socket, not server socket
received = client_socket.recv(BUFFER_SIZE).decode()
filename, filesize = received.split(SEPARATOR)
# remove absolute path if there is
filename = os.path.basename(filename)
# convert to integer
filesize = int(filesize)

# start receiving the file from the socket
# and writing to the file stream
progress = tqdm.tqdm(range(filesize), f"Receiving {filename}", unit="B", unit_scale=True, unit_divisor=1024)
with open(filename, "wb") as f:
    while True:
        # read 1024 bytes from the socket (receive)
        bytes_read = client_socket.recv(BUFFER_SIZE)
        if not bytes_read:    
            # nothing is received
            # file transmitting is done
            break
        # write to the file the bytes we just received
        f.write(bytes_read)
        # update the progress bar
        progress.update(len(bytes_read))

progress.close()
# close the client socket
client_socket.close()
# close the server socket
s.close()

and the other one called client.py :

import socket
import tqdm
import os

SEPARATOR = "<SEPARATOR>"
BUFFER_SIZE = 4096 # send 4096 bytes each time step

# the ip address or hostname of the server, the receiver
host = "192.168.1.12"

# the port, let's use 5001
port = 5001

# the name of file we want to send, make sure it exists
filename = "data.txt"

# get the file size
filesize = os.path.getsize(filename)

# create the client socket
s = socket.socket()

print(f"[+] Connecting to {host}:{port}")
s.connect((host, port))
print("[+] Connected.")

# send the filename and filesize
s.send(f"{filename}{SEPARATOR}{filesize}".encode())

# start sending the file
progress = tqdm.tqdm(range(filesize), f"Sending {filename}", unit="B", unit_scale=True, unit_divisor=1024)
with open(filename, "rb") as f:
    while True:
        # read the bytes from the file
        bytes_read = f.read(BUFFER_SIZE)
        if not bytes_read:
            # file transmitting is done
            break
        # we use sendall to assure transimission in 
        # busy networks
        s.sendall(bytes_read)
        # update the progress bar
        progress.update(len(bytes_read))
# close the socket
s.close()

Here is what I tried:

I checked the code over and over for any mistake. The problem is that the file is received empty with 0 bytes although it contained a string before sending.

How can I fix this problem, any help or suggestion will be much appreciated.

It seems you're running server and client in the same directory, and the server truncates the file before the client gets to read from it.