Socket Basics

https://docs.python.org/2/library/socket.html?highlight=pton\#module-socket

• To create a socket:

import socket

s = socket.socket(addr_family, type)

• Address Families:

socket.AF_INET Internet protocol (IPv4)

socket.AF_INET6 Internet protocol (IPv6)

• Socket Types:

socket.SOCK_STREAM Connection based stream (TCP)

socket.SOCK_DGRAM Datagrams (UDP)

Creating a socket is only the first step

s = socket(AF_INET, SOCK_STREAM)

Further use depends on application

• Server - Listen for incoming connections
• Client - Make an outgoing connection

TCP Server code will deal with TWO (or more) sockets

• The first socket is created by socket() and is used to LISTEN
• The other sockets are returned by accept() after a client connects to the listening socket. This new socket is used for data transfer to that specific client
• Accept() returns two values, the socket, and the IP of the other side.

Keep in mind

• Calls to accept() will NOT alter the LISTENING socket
• By default, accept() will block until a connection is received