Basics of socket API

Introducing `socket`

The socket module provides access to the standard socket interface
It is used to handle many different networking protocols
Most importantly, it handles the IP, which includes TCP and UDP protocols
This module is very low-level
- It provides direct access to the network functions provided by the operating system

Describing Address Families

Some socket functions require the specification of an address family
This family specifies the network protocol being used
The following constants are defined for this purpose:
- AF_BLUETOOTH: Bluetooth protocol
- AF_INET: IPv4 protocols (TCP; UDP)
- AF_INET6: IPv6 protocols (TCP; UDP)
- AF_NETLINK: Netlink Interprocess Communication
- AF_PACKET: Link-level packets
- AF_UNIX: UNIX domain protocols
Obviously, AF_INET and AF_INET6 are the most popular

Describing Socket Types

Some socket functions require the specification of a socket type
The socket type specifies the type of communication to be used within a given protocol family
The following constants are defined for this purpose:
- SOCK_STREAM: TCP Connection
- SOCK_DGRAM: UDP Datagrams
- SOCK_RAW: Raw socket
- SOCK_RDM: Reliable datagrams
Obviously, SOCK_STREAM and SOCK_DGRAM are the most popular

Describing `AF_INET` Addressing

In order to perform any communication on a socket, we need to specify a destination address
The form of the address depends on the address family of the socket
Internet applications using IPv4 are specified as a tuple
Specifically, this tuple looks like (host, port)
The following are some examples:

('www.python.org', 80)
('66.113.130.182', 25)

If host is the empty string, then it accepts any address
This is typically used by servers when they want any client to connect
Python uses DNS to resolve the host name into an IP address
Meaning, we may get different IP addresses each time when specifying a host like www.python.org

References

Previous

Next

The selectors Module

socket.create_connection