Function tryLockBlock

e2e/src/ports.ts:139–144

(block: number)

// the suite's lifetime means two suites racing for the same block can never
// both win (the second bind EADDRINUSEs and walks on).
const tryLockBlock = (block: number): Promise<Server | undefined> =>
  new Promise((done) => {
    const server = createServer();
    server.once("error", () => done(undefined));
    server.listen(block + LOCK_OFFSET, "127.0.0.1", () => done(server));
  });

/**
 * Claim a free set of ports for a target and publish them via env. Starts at