def readnbytes(sock, n):
    return sock.recv(n)   # can return less than n bytes

def readnbytes(sock, n):
    buff = b''
    while n > 0:
        b = sock.recv(n)
        buff += b
        if len(b) == 0:
            raise EOFError          # peer socket has received a SH_WR shutdown
        n -= len(b)
    return buff

def readnbyte(sock, n):
    buff = bytearray(n)
    pos = 0
    while pos < n:
        cr = sock.recv_into(memoryview(buff)[pos:])
        if cr == 0:
            raise EOFError
        pos += cr
    return buff

from socket import *

s = socket()
s.bind(('',5000))
s.listen(1)
c,a = s.accept()
with c.makefile() as f:
        while True:
                data = f.read(5)
                if not data: break
                print(data)

from socket import *
import time

s = socket()
s.connect(('localhost',5000))
s.sendall(b'123')
time.sleep(.5)
s.sendall(b'451234')
time.sleep(.5)
s.sendall(b'51234')
s.close()

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