TCP transports an ordered stream of bytes. It preserves order and lets us detect when the connection closes, but it does not know the logical boundaries of IRC messages.

Three valid recv() results

If the client sends:

NICK rox\r\n
USER roxana 0 * :Roxana Stancu\r\n

the server could receive:

1. Both commands in one call.
2. One command per call.
3. Fragments such as NI, CK rox\r\nUSER ro, and the remainder later.

All three cases are valid from TCP’s perspective. We therefore must not process everything returned by recv() as though it were a complete message.

A persistent buffer for each client

Each connection must preserve the bytes that do not yet form a complete line. The conceptual algorithm is:

append received bytes to the client buffer
while the buffer contains CRLF
    extract one complete line
    remove that line from the buffer
    parse and dispatch the command
keep the remaining partial data for the next read event

The last step is important. The remaining fragment is not an error and must not be discarded: it may be the beginning of the next command.

Multiple lines in one read

Processing only the first line is also insufficient. When several commands arrive together, the server must keep extracting lines until the buffer no longer contains a complete terminator. Processing order must match receive order.

This explains a common bug: manual tests work command by command but fail when a complete registration block is pasted. The problem is not necessarily in PASS, NICK, or USER; it may be in the layer that separates the TCP stream into IRC lines.

Limits and safety

An unbounded buffer would allow a client to send data indefinitely without completing a line. A robust implementation must define:

• The maximum accepted IRC line length.
• The maximum pending buffer size.
• Behavior for invalid data or a connection closed midway through a message.
• Tests for fragmentation, concatenation, and partial writes.

The key idea

Line-oriented protocols run on top of TCP, but their messages do not align with socket reads. Framing is the application’s responsibility.

irc-netlab is my project for building that environment around an IRC service.

The complete cycle

The first goal is not to support every imaginable scenario. It is to achieve a small, reliable, and repeatable local cycle:

validate
-> start
-> wait until ready
-> report status
-> stop
-> clean up
-> report result

Every step needs an observable result. If the service does not start, the lab must explain why. If a test fails, it must preserve evidence. If execution ends unexpectedly, it must still clean up the processes and resources it owns.

Independence before generalization

irc-netlab will be the first lab in an ecosystem that could include HTTP, TCP, DNS, or WebSocket. That does not mean they should all share a large abstraction from day one.

The initial rules are:

• Each lab exposes capabilities through public contracts.
• Labs do not depend on one another.
• A lab must work without the orchestrator.
• The future netlab-qa consumes contracts; it does not become a dependency of the labs.

This direction makes it possible to learn from a real implementation before designing a generic platform that might not match actual needs.

An installable and verifiable foundation

The first phase focuses on the foundation:

• Python 3.12 and a src layout.
• An installable package and console entry point.
• A CLI with help, version, and defined exit codes.
• Unit and integration tests.
• Ruff and validation of the generated wheel.
• Documented requirements, architecture, and decisions.

This foundation does not yet run the complete cycle. Publishing that limitation avoids confusing a sound project structure with functionality that does not yet exist.

Next milestone

The next useful result will be controlling a real IRC service from start to finish: starting it, detecting readiness, stopping it, and proving that no orphaned resources remain. From there, each additional capability can grow from real evidence.