WebSocket leaves TCP connection open after calling close

Version: Deno 1.45.5

Steps: start the server, start the client, wait for the client to call method close. Check the connections, I use ss -atn | grep 3333 on linux (can use lsof -i TCP:3333 on macos). I still see the tcp connection established and it’s still there several minutes after.

This looks unexpected to me. My use case - lets say there is some server issue so I wasn’t able to open a ws connection after a few seconds. I would keep trying to close and open another ws connection (with some delay). But that would keep leaking TCP connections.

LISTEN    0      128        127.0.0.1:3333         0.0.0.0:*           
ESTAB     0      0          127.0.0.1:45680      127.0.0.1:3333        
ESTAB     0      0          127.0.0.1:3333       127.0.0.1:45680

Repro scripts

Server - establishes TCP connections and prints received data to stdout, does not implement web socket protocol

const listener = Deno.listen({
  hostname: '127.0.0.1',
  port: 3333,
  transport: 'tcp',
});

for await (const conn of listener) {
  console.log('connected');
  readLoop(conn);
}

async function readLoop(conn: Deno.TcpConn) {
  const buf = new Uint8Array(1024 * 1024);
  const decoder = new TextDecoder();

  while (true) {
    const nread = await conn.read(buf);
    if (nread === null) {
      console.log('eof');
      break;
    }
    const txt = decoder.decode(buf.slice(0, nread));
    console.log('read', txt);
  }

  conn.close();
}

Client - opens a websocket connection and closes it after 1 second regardless of the result.

const socket = new WebSocket('http://localhost:3333');

setTimeout(() => {
  socket.close();
  console.log('Called close');
}, 1000);

denoland / deno

WebSocket leaves TCP connection open after calling close #25126

Repro scripts