01 Connectionless Sockets
• Connectionless Sockets
• Socket process for connectionless clients
and servers
• socket() Module Function
• Socket Object (Built-In) Methods
• The SocketServer Module
Connectionless Sockets
No connection is necessary before communication
can begin.
No guarantees of sequencing, reliability, or
nonduplication in the process of data delivery.
User Datagram Protocol (UDP)
To create UDP sockets, we must use
SOCK_DGRAM as the socket type.
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Connectionless Sockets
These sockets also use the Internet Protocol to find
hosts in the network.
This system also has a more general name, going by
the combined names of both of these protocols
(UDP and IP), or UDP/IP.
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Socket process for connectionless
clients and servers
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Socket() Module Function
To create a socket, you must use the socket.socket()
function, which has the general syntax:
Socket (socket_family, socket_type, protocol=0)
The socket_family is either AF_UNIX or AF_INET,
and the socket_type is SOCK_ DGRAM.
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Socket() Module Function
The protocol is usually left out, defaulting to 0.
To create a UDP/IP socket
udpSock = socket.socket
(socket.AF_INET, socket.SOCK_DGRAM)
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Socket Object (Built-In) Methods
General Socket Methods
s.recvfrom() s.recvfrom_into() s.sendto()
Receive Receive UDP Transmit
UDP message into UDP
message specified buffer message
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Socket Object (Built-In) Methods
Blocking-Oriented Socket Methods
s.setblocking()
Set blocking or non-blocking mode of socket
s.settimeout()
Set timeout for blocking socket operations
s.gettimeout()
8 Get timeout for blocking socket operations
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Socket Object (Built-In) Methods
File-Oriented Socket Methods
s.fileno() File descriptor of socket
s.makefile() Create a file object associated with socket
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Socket Object (Built-In) Methods
Data Attributes
s.family
The socket family
s.type
The socket type
s.proto
The socket protocol
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The Socket Server Module
BaseServer Contains core server functionality and hooks
for mix-in classes
TCPServer/ Basic networked synchronous
UDPServer TCP/UDP server
UnixStreamServer / Basic file-based synchronous
UnixDatagramServer TCP/UDP server
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The Socket Server Module
ForkingMixIn /
ThreadingMixIn
Core forking or threading functionality; used only as
mix-in classes with one of the server classes to
achieve some a synchronicity
ThreadingTCPServer/
ThreadingUDPServer
Combination of ThreadingMixIn and TCPServer/
UDPServer
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The Socket Server Module
BaseRequestHandler
Contains core functionality for handling service requests;
used only for derivation
StreamRequestHandler /
DatagramRequestHandler
Implement service handler for TCP/UDP servers
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User Datagram Protocol
02 (UDP)
• User Datagram Protocol (UDP)
• Differences between the TCP and UDP
• Python Internet modules
• Implementing the Client
• Implementing the Server
User Datagram Protocol (UDP)
UDP is typically used in applications that require little
overhead and higher network throughput, such as
multimedia streaming protocols.
It is capable of transmitting data to multiple
endpoints simultaneously because a connection is
not bound to a single address.
In environments where there is difficulty transmitting
to the destination, information may have to be re-
transmitted several times before the complete
2 message is received.
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Differences between the TCP and UDP
TCP UDP
Service Service
Provide connection setup between client
connectionless
and server processes
Reliable data transfer between sending
and receiving processes by using flow
Unreliable
control, sequence numbers,
acknowledgements, and timer
Sender will not overwhelm receiver No
Throttle sender when network overloaded No
Timing, minimum throughput guarantees, The same with
3 security TCP
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Python Internet modules
Protocol Common Function Port No Python module
httplib, urllib,
HTTP Web pages 80
xmlrpclib
NNTP Usenet news 119 nntplib
FTP File transfers 20 ftplib, urllib
SMTP Sending email 25 smtplib
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Python Internet modules
Protocol Common Function Port No Python module
POP3 Fetching email 110 poplib
IMAP4 Fetching email 143 imaplib
Telnet Command lines 23 telnetlib
Gopher Document transfers 70 Gopherlib,urllib
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Implementing the Client
Import the socket python module, this can be done like so:
import socket
Declare the IP address that we will be trying to send our
UDP messages to as well as the port number.
UDP_IP_ADDRESS = "127.0.0.1”
UDP_PORT_NO = 6789
6 Message = "Hello, Server”
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Implementing the Client
Create the socket through which we will be sending our
UDP message to the server.
clientSock=
socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
Write the code that will send our UDP message:
clientSock.sendto(Message,(UDP_IP_ADDRESS,
UDP_PORT_NO))
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Implementing the Server
Server program will be continuously listening on defined
IP address and port number for any UDP messages.
import socket
UDP_IP_ADDRESS = "127.0.0.1"
UDP_PORT_NO = 6789
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Implementing the Server
When imported the socket module and declared IP
address and port number, we can create another
socket which will look exactly like the socket we
constructed in our client program.
serverSock = socket.socket(socket.AF_INET,
socket.SOCK_DGRAM)
serverSock.bind((UDP_IP_ADDRESS,
UDP_PORT_NO))
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Implementing the Server
The code that will keep the script continuously
listening to the server socket until its termination.
This takes form as a simple while loop, like so:
while True:
data, addr = serverSock.recvfrom(1024)
print ("Message: ", data)
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Building a Python
03 Networking Program
