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Writing a UDP Client Program

Writing a UDP Client Program

Let's now write a client to go with the server we wrote.

We'll cover the following...

The Server

Here’s the server code that we have so far for reference.

import socket
MAX_SIZE_BYTES = 65535 # Mazimum size of a UDP datagram
# Setting up a socket
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) 
port = 3000
hostname = '127.0.0.1'
s.bind((hostname, port))
print('Listening at {}'.format(s.getsockname()))
while True:
 data, address = s.recvfrom(MAX_SIZE_BYTES)
 message = data.decode('ascii')
 upperCaseMessage = message.upper()
 print('The client at {} says {!r}'.format(clientAddress, message))
 data = upperCaseMessage.encode('ascii')
 s.sendto(data, clientAddress)

Creating a Client Socket

Instead of explicitly binding the socket to a given port and IP as we did previously, we can let the OS take care of it. Remember ephemeral ports? Yes, the OS will bind the socket to a port dynamically. So all we really need is to create a UDP socket (line 3).

Python 3.5
import socket
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

In fact, we can check ...