Code running on PC:
import os
from socket import *
host = "192.168....." (IP address of pi)
port = 13000
addr = (host, port)
UDPSock = socket(AF_INET, SOCK_DGRAM)
while True:
    data = raw_input("Enter message to send or type 'exit': ")
    UDPSock.sendto(data, addr)
    if data == "exit":
        break
UDPSock.close()
os._exit(0)

Code running on Pi:

import os
from socket import *
host = ""
port = 13000
buf = 1024
addr = (host, port)
UDPSock = socket(AF_INET, SOCK_DGRAM)
UDPSock.bind(addr)
print ("Waiting to receive messages...")
while True:
    (data, addr) = UDPSock.recvfrom(buf)
    print ("Received message: " + data)
    if data == "exit":
        break
UDPSock.close()
os._exit(0)