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Grokking Computer Networking for Software Engineers

Writing a UDP Client Program

Explore how to build a UDP client program using Python socket programming. Understand creating a client socket with dynamic port binding, sending user input to a server, and receiving the server's response. This lesson helps you implement a simple client-server communication using UDP.

We'll cover the following...

The Server

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

Python 3.5
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 ...