code: function detectPortOrSystemd(port) {
    if (systemdSocket) {
      const passedSocketCount = parseInt(process.env.LISTEN_FDS, 10) || 0;
  
      // LISTEN_FDS contains number of sockets passed by Systemd. At least one
      // must be passed. The sockets are set to file descriptors starting from 3.
      // We just crab the first socket from fd 3 since sqlpad binds only one
      // port.
      if (passedSocketCount > 0) {
        console.log('Using port from Systemd');
        return Promise.resolve({ fd: 3 });
      } else {
        console.error(
          'Warning: Systemd socket asked but not found. Trying to bind port ' +
            port +
            ' manually'
        );
      }
    }
  
    return detectPort(port);
  }
docs: When --systemd-socket is passed we will try to acquire the bound socket directly from Systemd.  More info  https://github.com/rickbergfalk/sqlpad/pull/185 https://www.freedesktop.org/software/systemd/man/systemd.socket.html https://www.freedesktop.org/software/systemd/man/sd_listen_fds.html