Is it (or will it) be possible to develop custom actions for Watcher and plug them into a running instance ?
right now it's not possible. Are you missing something specific?
A common helper here is the possibility of using a watcher webhook to write to logstash http input and then either reuse an existing logstash plugin or write your own (a bit of ruby code).
Thanks for the update.
I wanted to connect to a server which does proprietary messaging over a TCP socket.
Trying to avoid building a solution on an intermediate server, be it logstash or whatever.
I would second the request to be able to write custom action. Actually I would contribute the source code back if you want it