Introducing Ping Watcher

Every now and then I find myself troubleshooting an issue at a remote customer site where hosts have limited connectivity to the rest of the world. For example, sometimes they can reach other private networks over a VPN, but apparently can't reach anything on the public Internet. In this scenario, the game is to deduce whether traffic is being dropped inbound or outbound. Unfortunately, there's no easy way to verify whether traffic is being dropped outbound beyond a device under your control.

So, last week I put together a simple tool to watch for ICMP echo requests (pings) sent to this site and publish a live stream of incoming traffic. This tool is Ping Watcher. (Get it? It watches pings.)

Ping Watcher employs Ajax and a simple back-end tied to a tshark process running on the public interface of this server. Send a ping, tshark catches it and writes it to round-robin memory structure (achieved using redis, and it will appear in Ping Watcher within a few seconds. Now you can confirm that traffic is at least getting from point A to the Internet, if not from the Internet to point B.

Hopefully this proves helpful to people. Let me know of any potential bugs or improvements you'd like to see.

And thanks to tbic and caaakeeey in #django on Freenode for some much-appreciate programming pointers!