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Date: Tue, 6 May 2014 09:05:22 +1000
Subject: Re: socket client and server in one application?
From: Chris Angelico <rosuav@gmail.com>
Cc: "python-list@python.org" <python-list@python.org>
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On Tue, May 6, 2014 at 8:37 AM,  <chris@freeranger.com> wrote:
> I'm using a dispatch method to receive and occasionally send data through=
 a serial port on a Raspberry Pi.  I think the dispatch method is essential=
ly a threaded approach, right?
>
> Now to receive serial data and send via socket, then occasionally receive=
 some socket based input and send out on the same serial port.  It's combin=
ing the client and server socket code into a single app (so I can have a si=
ngle connection to the serial port) that has me confused.  I don't see any =
discussion of that anywhere.
>

Threads would be easy. As I understand it, you have two bidirectional
connections, and you're simply linking them? Sounds like a very simple
proxy/tunnel. You don't need to multiplex, so all you need is two
threads: one reading from the socket and writing to the serial port,
and one reading from the serial port and writing to the socket. The
code would look something like this:

serial_port =3D open(...)
tcp_socket =3D socket.create_connection(...)
# initialize them both, do whatever setup is needed

def socket_to_serial():
    while True:
        data =3D tcp_socket.recv(4096)
        serial_port.write(data)

Thread.Thread(target=3Dsocket_to_serial).start()

while True:
    data =3D serial_port.read(4096)
    tcp_socket.send(data)


Two simple loops, running concurrently. Pretty straight-forward as
threads. Both of them will fall idle in their read/recv calls, so
threading works very nicely here.

ChrisA