I run a traffic proxy and the traffic proxy bundle some stats into a custom binary format and can send them to an endpoint via TCP socket. I cannot install a filebeat or such sort in this proxy. So, I want to create a TCP server listener in the Elastic ecosystem to listen to these records sent via TCP and convert them to some JSON before I push them to Logstash.
There are various options, from creating a Logstash input plugin to writing a standalone server that transforms the custom binary protocol to JSON. I'll move this to the Elastic Stack category - this doesn't really have anything to do with APM. Hopefully someone watching that category has some more specific guidance.