"""A simple UDP server.  The first byte received indicates how many bytes
   are in the application payload.  These are displayed in hexadecimal."""
__author__ = 'Josiah Yoder, Phileas Fogg'

import socket

print 'Starting udpserver.py'

server_name = 'localhost'
server_port = 12000

server_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
server_socket.bind((server_name,server_port))

message,clientAddress = server_socket.recvfrom(2048)

first_byte = ord(message[0])

print 'from {0}, received first byte {1:02x}'.format(clientAddress,first_byte)
if len(message) < first_byte+1:
    raise Exception('Message has invalid format: Header specifies {0} '
                    'bytes, but only {1} bytes found'.format(first_byte,len(message)))

print 'Message length:',len(message)

for i in range(0,first_byte):
    print 'payload byte {0}: {1:02x}'.format(i,ord(message[i+1]))