RFID using Python Socket ( Low Level Commands)

(From your question)

s.sendall(MESSAGE)
data = s.recv(BUFFER_SIZE)
s.close()

You are sending data via send, immediately asking for the response data, then closing the socket. Enough time will not have passed for you to get a response. For testing, try placing a time delay between.

import time
s.sendall(MESSAGE)
time.sleep(5)
data = s.recv(BUFFER_SIZE)
print(data)
s.close()

You can also wait for the incoming data;

import time
s.sendall(MESSAGE)
while data is None:
    data = s.recv(BUFFER_SIZE)
    print "No data, waiting...."
    time.sleep(0.5)

print "Data arrived"
incoming = data.decode('utf-8')
print incoming
# Process Data

I did personally have an issue if my buffer size was too small -- I had to catch the timeout exception to deal with it. Perhaps try increasing your buffer size.

Below is something close to the actual code I use for my application; It python 3.x, and you will have to condition it a bit -- but it works for me.

            try:
                data = s.recv(buf_len)
                if data is not None and len(data) > 0:
                    while True:
                        new_data = s.recv(buf_len)
                        if new_data is None or len(new_data) == 0:
                            break
                        data = data + new_data

            except socket.timeout:
                if data is not None and self.callback is not None:
                    logger.debug(f"Received packet: {data}")   

incoming = data.decode('utf-8')
print incoming
# Process Data