networking question: 2-way messaging w/o wireless modem config?

[Mark H Harris]

On 4/17/14 11:20 AM, haiticare2011 at gmail.com wrote:
> I have a Raspberry Pi board with a wireless usb modem on it.
> I wish to be able to message 2-way with the board from
> across the internet, without having to open ports on the wireless modem. Is there
>   a way to do this? I have been looking at udp, but imagine that a udp packet is
> allowed in, but not out?
> The amount of data transmission I want is very small, maybe lt 30 bytes.

The answer depends on how you setup your wireless modem | router. There 
are many ways to set this up depending on your project goals. If you're 
trying to setup a sniffer (well, just don't do that, its not nice).

If you were trying to setup a micro server on my network (for instance), 
well, you couln't, because I don't permit the outgoing connection 
without authorization and port (actually, same is true for incoming 
connections. I would have to setup auth and port for you to connect your 
Pi as a micro server on my wireless network. Most public access points 
are blocked (peer to peer) too (if they're smart).

For legitimate non trivial setups (not experiments) you want to control 
the connection with auth and ports.

A word of caution about udp. If the data you are sending is contained in 
one datagram (one packet), then no problem; however, if you are sending 
multiple packets over the WAN it can be a big problem because the upd 
in|out does not guarantee correct packet ordering.

Is there a python question in here somewhere?

marcus