Use Python's Crypto module which supports AES. You need a symmetric key (same key used to encrypt and decrypt). The same key can be generated in both server and client if the same passphrase and the initialization vector(IV) are used.

Summary: 1. Same key to be used to encrypt and decrypt 2. Use Crypto.Cipher.AES

AES has methods to generate key, encrypt and decrypt data. Following links have the actual code. pycrypto stackoverflow

Client - Call this method to encrypt your data and send the encrypted data

from Crypto.Cipher import AES

def do_encrypt(message):
    obj = AES.new('This is a key123', AES.MODE_CBC, 'This is an IV456')
    ciphertext = obj.encrypt(message)
    return ciphertext

Server - Receive data and call this method to decrypt the data

from Crypto.Cipher import AES

def do_decrypt(ciphertext):
    obj2 = AES.new('This is a key123', AES.MODE_CBC, 'This is an IV456')
    message = obj2.decrypt(ciphertext)
    return message

This is a sample code, make sure you choose a strong passphrase and IV.