Incorrect throughput output via Python between server and client

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Python

server

TCP/IP

I am writing a python code to find throughput between server and client. It is based on speedtest.net functionality where I am sending a dummy file to calculate the speed. The problem I am facing is unreliable throughput output. I will appreciate your suggestions on the same. Here is the code.

server.py

import socket

import os

port = 60000
s = socket.socket()
host = socket.gethostname()
s.bind((host, port))
s.listen(5)

print 'Server listening....'

while True:
   conn, addr = s.accept()    
   print 'Got connection from', addr
   data = conn.recv(1024)
   print('Server received', repr(data))

   filename='akki.txt'
   b = os.path.getsize(filename)
   f = open(filename,'rb')
   l = f.read(b)

   while (l):

      conn.send(l)

      l = f.read(b)
   f.close()

   print('Done sending')
   conn.send('Thank you for connecting')
   conn.close()

Client.py

import socket
import time
import os

s = socket.socket()
host = socket.gethostname()
port = 60000

t1 = time.time()
s.connect((host, port))
s.send("Hello server!")

with open('received_file', 'wb') as f:
    print 'file opened'
    t2 = time.time()
    while True:

        data = s.recv(1024)

        if not data:
            break

        f.write(data)
        t3 = time.time()

print data
print 'Total:', t3 - t1
print 'Throughput:', round((1024.0 * 0.001) / (t3 - t1), 3),
print 'K/sec.'
f.close()
print('Successfully received the file')
s.close()
print('connection closed')

Output when sending akki.txt

Server Output

Server listening....
Got connection from ('10.143.47.165', 60902)
('Server received', "'Hello server!'")
Done sending

Client output file opened

Raw timers: 1503350568.11 1503350568.11 1503350568.11
Total: 0.00499987602234
**Throughput: 204.805 K/sec.**
Successfully received the file
connection closed
Output for ak.zip ( which is bigger file)

Client output file opened

Total: 0.0499999523163
**Throughput: 20.48 K/sec.**
Successfully received the file
connection closed

What I have tried:

The output is changing. Like, If I am using file with smaller size, the throughput is more, however if I am sending the file with bigger size, the throughput is less. I am looking for the solution to get the constant throughput speed between two peers.