Building a Concurrent TCP Echo Server
A networking example becomes a service when it remains correct under concurrency, malformed input, slow peers, overload, and shutdown. Accepting multiple clients is only the first step. The server also needs explicit policies for how much work it admits, how long it waits, how it frames messages, and how it releases resources.
This chapter builds a persistent concurrent TCP echo service in two implementations:
- A Python server using
asyncio - A Java 21 server using one virtual thread per admitted connection
Both servers listen on port 5006 and implement the same byte-level protocol. A shared Python load client can open many persistent connections and validate either implementation.
The goal is not to crown one concurrency model as universally best. It is to build a complete service whose protocol, resource limits, failure handling, metrics, and shutdown behavior remain consistent regardless of the internal concurrency mechanism.