How to receive a data file of unknown length using a python socket?

[twgray]

On Jul 18, 4:43 pm, Irmen de Jong <irmen.NOS... at xs4all.nl> wrote:
> twgray wrote:
> > I am attempting to send a jpeg image file created on an embedded
> > device over a wifi socket to a Python client running on a Linux pc
> > (Ubuntu).  All works well, except I don't know, on the pc client side,
> > what the file size is?  
>
> You don't. Sockets are just endless streams of bytes. You will have to design some form
> of 'wire protocol' that includes the length of the message that is to be read.
> For instance a minimalistic protocol could be the following:
> Send 4 bytes that contain the length (an int) then the data itself. The client reads 4
> bytes, decodes it into the integer that tells it the length, and then reads the correct
> amount of bytes from the socket.
>
> --irmen

Thanks for the reply.  But, now I have a newbie Python question.  If I
send a 4 byte address from the embedded device, how do I convert that,
in Python, to a 4 byte, or long, number?