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Hi folks,I'm working on a project for work where we want to have a slow link between two sites across a road (with a few trees in the way) to capture a JPG image from a Raspberry Pi every minute. Eventually the site will have some decent network connectivity (probably fibre to our main building) but in the mean time it's a building site so we don't want to risk laying fibre and then having a digger go through it.
The solution I've come up with is two Raspberry Pis (older model B that we had kicking around) with a Slice Of Radio module on each one. For those of you who aren't familiar with it, the Slice Of Radio module basically converts the serial connection on a Pi to RF (800 and something MHz I think) and on other Pi it converts it back to serial. In a way it's like a null modem connection over RF (at a whopping 115200 bps).
So I've managed to get the Pis to talk to each other via serial. I've configured PPP on each Pi and they can connect to each other and I can ping each Pi (with IP forwarding enabled I can also ping the Internet and do DNS lookups over the RF connection). However when I try and grab something over HTTP this is where it falls flat on it's face.
Here's an example... root@cottage:~# wget http://192.168.2.50:8 --2015-05-27 19:37:35-- http://192.168.2.50 Connecting to 192.168.2.50:80... connected. HTTP request sent, awaiting response...That's all it does. Checking the Apache logs on the remote Pi it can tell there's been a connection made but it's not sending any data. If I try SSH it also doesn't appear to do anything. So I'm wondering if something is stopping TCP from working over the PPP link. ICMP and UDP work (or at least appear to work, DNS resolves and pings work) so this is leaving me stumped.
If it helps this is the latest command I've been using on each side (just swapping the IP addresses around)
pppd proxyarp mtu 1280 persist nodeflate noauth lcp-echo-interval 10 crtscts lock 10.10.1.2:10.10.1.1 /dev/ttyAMA0 115200
I've tried changing the MTU too but this also doesn't appear to make any difference.
I just wondered if any of you out there have any experience of PPP and if you might be able to shed some light on it? (Last time I setup a PPP dialin server was back in 2003 and I can't for the life of me remember how I did it).
Rob -- The Mailing List for the Devon & Cornwall LUG http://mailman.dclug.org.uk/listinfo/list FAQ: http://www.dcglug.org.uk/listfaq