The htonl() function in Python

Overview:

The function htonl() of Python socket module converts a 4 byte integer from host byte order to network byte order and returns the result as an integer.
If the byte order of the host platform is same as the network order the original parameter value is returned without any conversion. Otherwise, htonl() swaps the bytes such that byte[0]= byte[3], byte[1]= byte[2], byte[2]=byte[1], byte[3]=byte[0].

Example:

# Example Python program that converts a 32 bit integer
# from host order to network order using the
# function socket.htonl()

import struct
import socket
import sys

# Endianness of the host platform
print("The host system runs on %s endian platform"%sys.byteorder)

# Number to be converted
#num = 1022
num = 1048572
print("Number to convert: 0x%X"%num)

# Print in big endian
beBytes = struct.pack("!I", num)
print("In big endian format - output of struct.pack():%s"%beBytes)

beBytes1 = num.to_bytes(4, byteorder = 'big')
print("In big endian format - output of to_bytes:%s"%beBytes1)

# Print in little endian
leBytes = struct.pack("I", num)
print("In little endian format - output from struct.pack():%s"%leBytes)

leBytes1 = num.to_bytes(4, byteorder = 'little')
print("In little endian format - output from to_bytes():%s"%leBytes1)

# Reconstruct the number from big endian
netNumber = int.from_bytes(beBytes1, 'big')
print("Reconstructed from big endian order: %d"%netNumber)

# Reconstruct the number from little endian
netNumber = int.from_bytes(leBytes1, 'little')
print("Reconstructed from little endian order: %d"%netNumber)

# Now...convert the number to network byte order
nw = socket.htonl(num)
print("Integer after convertion using htonl():")
print(nw)

# Print the translated integer as bytes...the translated integer is
# also stored in little endian (as host is little endian)
nwOrder = nw.to_bytes(4, byteorder = 'little')
print("Output of htonl:%s"%nwOrder)

# Reconstruct from bytes
print(int.from_bytes(nwOrder, 'little')

Output:

The host system runs on little endian platform

Number to convert: 0xFFFFC

In big endian format - output of struct.pack():b'\x00\x0f\xff\xfc'

In big endian format - output of to_bytes:b'\x00\x0f\xff\xfc'

In little endian format - output from struct.pack():b'\xfc\xff\x0f\x00'

In little endian format - output from to_bytes():b'\xfc\xff\x0f\x00'

Reconstructed from big endian order: 1048572

Reconstructed from little endian order: 1048572

Integer after convertion using htonl():

4244573952

Output of htonl:b'\x00\x0f\xff\xfc'

4244573952