Python Program for Socket Networking

socket class

Socket families

• AF_UNIX socket - Address bound to a file system node and it's represented as a string(uses UTF-8 encoding).
• AF_INET - Address uses a pair (host, port), here host is a string represents either a host name in Internet domain example 'google.com' or an IPv4 address example '10.20.160.61' and port is an integer number.
• AF_INET6 - Address is a tuple (host, port, flow_info, scope_id), here host and port is like same as mentioned above point, flow_info and scope_id are optional, these denote sin6_flowinfo and sin6_scope_id members in struct sockaddr_in6 in C.
• AF_NETLINK - Address is a pair (pid, groups).
• AF_TIPC - TIPC is an open, non-IP based networked protocol
• AF_BLUETOOTH - supports protocols like BTPROTO_L2CAP, BTPROTO_RFCOMM, BTPROTO_HCI and BTPROTO_SCO.
• AF_ALG - Linux-only socket based interface to Kernel cryptography.

socket module

Some socket constants

• socket.AF_UNIX
• socket.AF_INET
• socket.AF_INET6

• socket.SOCK_STREAM
• socket.SOCK_DGRAM
• socket.SOCK_RAW
• socket.SOCK_RDM
• socket.SOCK_SEQPACKET

Socket Exceptions

• socket.error - This class was made an alias of OSError.
• socket.herror - subclass of OSError exception and raised for address-related errors when calling gethostbyname_ex() and gethostbyaddr() functions
• socket.gaierror - subclass of OSError exception and raised for address-related errors when calling getaddrinfo() and getnameinfo()
• socket.timeout - subclass of OSError exception and raised when a timeout occurs on a socket settimeout()

Some functions

• soket.socket - creating socket object.

  socket.socket(family=AF_INET, type=SOCK_STREAM, protocol_number=0, file_number=None)
  

• socket.socketpair - creating a pair of connected socket objects.

  socket.socketpair([family[, type[, protocol_number]]])
  

• socket.create_connection - Connecting TCP service listening on the address (tuple (host, port)) and return the socket object.

  socket.create_connection(address[, timeout[, source_address]])
  

• socket.getaddrinfo - function returns a list of tuples (family, type, protocol number, canonical name, socket address)

  socket.getaddrinfo(host, port, family=0, type=0, proto=0, flags=0)
  

• socket.gethostbyname - gets IPv4 address as a string from host name.

  socket.gethostbyname(hostname)
  

• socket.gethostname - gets the hostname of the local machine.

  socket.gethostname()
  

• socket.gethostbyaddr - get the host name (host_name, alias_name_list, ip_address_list) for given ip address where hostname is the primary host name.

  socket.gethostbyaddr(ip_address)
  

Python program to get ip address of internet domain name.

import socket                                                                   
                                                                                
port = 80                                                                       
try:                                                                            
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)                       
    print "Socket object is created"                                            
    host_ip = socket.gethostbyname('www.codingpointer.com')                     
except (socket.error, socket.gaierror) as ex:                                   
    print "socket error: %s" %(ex)                                              
else:                                                                           
    # connecting server                                                         
    s.connect((host_ip, port))                                                  
    print "Connected codingpointer.com on port == %s" %(host_ip)