Nest.js microservices can communicate with each other using different transports. It has its own server and client implementations and there is no example of how to send messages NOT using Nest.js.
But what if we have the legacy current codebase, and we're not ready to rewrite it with Nest.js yet?
This repository contains a custom TCP client written using TypeScript and Node.js which can communicate with the Nest.js TCP server.
It's not perfect, I personally think of it more as a proof of concept.
Reverse engineering showed that Nest.js uses the following TCP message format:
# {length}{delimiter}{data}
75#{"pattern":"example","data":{},"id":"ce51ebd3-32b1-4ae6-b7ef-e018126c4cc4"}
ID (data.id) is used for message pattern strategy (MessagePattern), without it, Nest.js treats the message as an event (EventPattern).