All the tables provided in the cheat sheets are also presented in tables below which are easy to copy and paste.

The Python Network Programming Cheat Sheet covers:

  • Required common installation modules: PIP and IDLE
  • Top python network programming libraries
  • Network forensics: Required python libraries and scripts
  • Python Keywords
  • Data Types, Math operators
  • Network Analysis with Python
  • The dnspython library
  • Socket Module (Berkley API interface)
  • Socket Types, Creating Sockets
  • Socket Examples
  • Script Examples
  • Parsing Modules

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What’s included in this cheat sheet

The following categories and items have been included in the cheat sheet:

Required common installation modules: PIP and IDLE

PIP (Python Package Installer)


$ sudo apt-get install python-pip

IDLE (Integrated Development and Learning Environment)


$ sudo apt-get install idle

Top python network programming libraries

Django


High-level Python Web framework for rapid development and pragmatic


pycos (formerly asyncoro)


Python framework for asynchronous, concurrent, network, distributed programming and distributed computing


Diesel


A clean API for writing network clients and servers. TCP and UDP supported. Bundles clients for HTTP, DNS, Redis, Riak and MongoDB.


Pulsar


Easy way to build scalable network programs


Twisted


Event-based framework for internet applications: HTTP clients and servers, SSHv2 and Telnet, IRC, XMPP, IMAPv4, POP3, SMTP, IMAPv4, POP3, SMTP, etc.


NAPALM


Network Automation and Programmability Abstraction Layer with Multivendor support - For dealing with dvice vendors


gevent


A coroutine -based Python networking library that uses greenlet to provide a high-level synchronous API on top of the libev or libuv event loop


Celery


Asynchronous task queue/job queue based on distributed message passing


Network forensics: Required python libraries and scripts

EDDIE Tool


System and network monitoring, security, and performance analysis agent for python


pypcap


Small packet capture tool based on python and pcap


Paramiko


Implementation of the SSHv2 protocol, providing both client and server functionality


pip


Package installer for python


The Python Package Index (PyPI)


Repository of software for the Python


Python Keywords

>>> import keyword
>>> print(keyword.kwlist)

Python 2.7.15+ ['and', 'as', 'assert', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'exec', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'not', 'or', 'pass', 'print', 'raise', 'return', 'try', 'while', 'with', 'yield']


Python 3.8.0 ['False', 'None', 'True', 'and', 'as', 'assert', 'async', 'await', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield']


Data Types

del


Delete objects


else


Conditional statement


except


Used in try-except blocks in error handling


finally


Used in try-except blocks in error handling, runs with or without errors


in


Check that a value is included in a sequence


import


Import module to current environment


lambda


Anonymous function


print


Standard print


try


Used in error handling


Math operators

**


Exponent 4 ** 2 = 16


%


Modulus/Remainder 43 % 5 = 3


//


Integer division 11 // 5 = 2


/


Division 11 / 5 = 2.2


*


Multiplication 3 * 3 = 9


-


Subtraction 8 - 3 = 5


+


Addition 2 + 2 = 4


==


Equal to


!=


Not equal to


<


Less than


>


Greater Than


<=


Less than or Equal to


>=


Greater than or Equal to


#


Can be used at the beginning of a line, or from within a line to the end of the line


Network Analysis with Python

Use NMAP with port scanner


$ pip install python-nmap

Commands to run NMAP scan


import nmap
nmScan = nmap.PortScanner()
nmScan.scan('10.1.0.0', '25-443')

NMAP commands used with python


nmScan.scaninfo() # {'tcp': {'services': ‘25-80’, 'method': 'connect'}}
nmScan.all_hosts()
nmScan['10.1.0.0'].hostname()
nmScan['10.1.0.0'].state()
nmScan['10.1.0.0'].all_protocols()
nmScan['10.1.0.0']['tcp'].keys() # Results -[80, 25, 22, 135]
nmScan['10.1.0.0'].has_tcp(25) # Result True/False
nmScan['10.1.0.0'].has_tcp(21) # Result False/True

The dnspython library

Installation


$ pip install dnspython

Basic DNS query


import dns.resolver
name = 'google.com'
for qtype in 'A', 'AAAA', 'MX', 'NS', 'TXT', 'SOA':
answer = dns.resolver.query(name,qtype, raise_on_no_answer=False)
if answer.rrset is not None:
print(answer.rrset)

Get MX target and name preference


import dns.resolver


answers = dns.resolver.query('dnspython.org', 'MX')
for rdata in answers:
print ('Host', rdata.exchange, 'has preference', rdata.preference)

Socket Module (Berkley API interface)

Primary Functions an Methods


socket() • ind() • listen() • accept() • connect() • connect_ex() • send() • recv() • close()


Socket Types

SOCK_STREAM


For TCP protocols • Reliable transmission • Packet sequence • Connection-oriented • Bidirectional


SOCK_DGRAM


For UDP protocols • Unreliable transmission • No sequence of packets • Connectionless(UDP) • Not Bidirectional


Creating Sockets

import socket # Imports the socket method

socket.socket() # Function that creates socket

sock = socket. socket (socket family, socket type, protocol=value)

Socket Family


AF_UNIX or AF_INET

Socket Type


SOCK_STREAM or SOCK_DGRAM for TCP & UDP respectively


• e.g. TCP - UDP2 = socket. socket (socket.AF_INET, socket.SOCK_DGRAM)


• e.g. UDP - TCP2 = socket. socket (socket.AF_INET, socket.SOCK_STREAM)


Client socket method


connect()

Server socket method


bind() • listen(backlog) • accept()

TCP socket methods


s.recv() # Receive TCP packets
s.send() #Send TCP packets

UDP socket methods


s.recvfrom() # Receives UDP packets
s.sendto() # Transmits UDP packets

More Socket Methods


close()

Close the socket connection


gethostname()

Returns a string which includes the hostname of the current PC


gethostbyname()

Returns a string which includes the hostname and IP address of the current PC


listen()

Setup and start TCP listener


bind()

Attach (host-name, port number) to the socket


accept()

TCP client connection wait


connect()

Initiate TCP server connection


TCP Socket Methods

mysocket.accept()

Returns a tuple with the remote address that has connected


mysocket.bind( address )

Attach the specified local address to the socket


mysocket.connect( address )

Data sent through the socket assigns to the given remote address


mysocket.getpeername()

Returns the remote address where the socket is connected


mysocket.getsockname()

Returns the address of the socket’s own local endpoint


mysocket.sendto(data, address)

Force a data packet to a specific remote address


Socket Blocking


setblocking(1)

Setup block


setblocking(0)

Remove / un-setup block


Get port number using domain name


import socket
socket.getservbyname('domain name')

Check support for IPV6


import socket
socket.has_ipv6 # Answer is TRUE or FALSE

getaddrinfo() - Bind Server to a Port


from socket import getaddrinfo
getaddrinfo(None, 'FTP', 0, socket.SOCK_STREAM, 0, socket.AI_PASSIVE)
[(2, 1, 6, '', ('0.0.0.0', 21)), (10, 1, 6, '', ('::', 21, 0, 0))]

Socket Examples

Client-side socket example


import socket
s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
host=socket.gethostname()
port=1111
myserver.bind((host,port)) # replace myserver and myclient with repsctive IPs
myserver.listen(5)
while True:
myclient,addr=myserver.accept()
print("Connected to {str(addr)}")
myclient.send(msg.encode("ascii"))
myclient.close()

Client-side Socket example with Comments


# import the socket library
import socket


# create a socket object
s = socket.socket()
print ("Socket created")


# reserve a port on the computer which can be anything
port = 1111


# bind to the port
# empty string in the IP field instead of an IP makes server listen to requests
# coming from other computers on the network
s.bind(('', port))
print ("socket binded to %s" %(port))


# make socket into listening mode
s.listen(5)
print ("socket is listening")


# loop until user interrupt it or an error occurs
while True:


# Establish connection with client.
c, addr = s.accept()
print ('Got connection from', addr)


# send a thank you message to the client.
c.send('Thank you for connection')


# Close the connection
c.close()

Script Examples

Create list of devices


>>>devices = ['SW1', 'SW2', 'SW3']

Create VLAN dictionary list


vlans = [{'id': '100', 'name': 'staff'}, {'id': '200', 'name': 'VOICE'},
{'id': '300', 'name': 'wireless'}]

Write functions to collect commands and push to the network


>>>def get_commands(vlan, name):
commands = []
commands.append('vlan ' + vlan)
commands.append('name ' + name)


return commands


>>> def push_commands(device, commands):
print('Connecting to device: ' + device)
for cmd in commands:
print('Sending command: ' + cmd)

Create VLANs in multiple switches using python script


>>>for vlan in vlans:
id = vlan.get('id')
name = vlan.get('name')
print('\n')
print('Configure VLAN:' + id)
commands = get_commands(id, name)
for device in devices:
push_commands(device, commands)
print('\n')

Citation: https://www.oreilly.com/library/view/network-programmability-and/9781491931240/ch04.html


Disable router interface using python command


>>> from push import push_commands
device = 'router2'
commands = ['interface Eth0/1', 'shutdown']
push_commands(device, commands)

Parsing Modules

argparse()

The argparse module makes it easy to write user-friendly command-line interfaces. The program defines what arguments it requires, and argparse will figure out how to parse those out of sys.argv


Creating a parser


>>> parser = argparse.ArgumentParser(description='Process some integers.')

Adding arguments


>>> parser.add_argument('integers', metavar='N', type=int, nargs='+',
... help='an integer for the accumulator')
>>> parser.add_argument('--sum', dest='accumulate', action='store_const',
... const=sum, default=max,
... help='sum the integers (default: find the max)')

Parsing arguments


>>> parser.parse_args(['--sum', '7', '-1', '42'])
Namespace(accumulate=, integers=[7, -1, 42])