Python network programming cheat sheet

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))]

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()