tcp-sprint/README.md

# TCP Sprint

This script demonstrates the risk of interleaving writes when cloning
`TcpStream` handles across threads, re:
[this discussion in the Servo Zulip](https://servo.zulipchat.com/#narrow/channel/263398-general/topic/TcpStream.3A.3Atry_clone.28.29.20thread.20safety.20in.20devtools/with/578172763).

It works by spawning 3 threads: 2 TCP clients, each of which sends predictable
chunks of bytes over a shared connection with `TcpStream::write_all()`, and 1
TCP listener, which tests whether messages arrive contiguously or scrambled
together.

Messages consist of the range `0x00..=0xff`, repeated to fill the desired
message size.

## Usage

```sh
cargo run --release <message size in bytes>
```

## Results

A message size of 1024 bytes can be sufficient to trigger fragmentation when
running an optimized build. Results from debug builds are hit-or-miss depending
on the host system: they may have no issues with fragmentation regardless of
message size, or they may encounter issues at closer to 4096 bytes.

![Terminal screenshot showing results of running script with 512 and 1024 byte messages. The first run has no errors, while the second one displays two "out of order" warnings.](./screenshot.png)