write_stream: Process output in a streaming manner.
Description
This is the most general way of processing the response from the server -
you receive the raw bytes as they come in, and you can do whatever you want
with them.
Usage
write_stream(f)
Arguments
f
Callback function. It should have a single argument, a raw
vector containing the bytes recieved from the server. This will usually
be 16k or less. The return value of the function is ignored.