code: func (h Handler) ServeTCP(pluginName, addr, daemonDir string, tlsConfig *tls.Config) error {
  	l, spec, err := newTCPListener(addr, pluginName, daemonDir, tlsConfig)
  	if err != nil {
  		return err
  	}
  	if spec != "" {
  		defer os.Remove(spec)
  	}
  	return h.Serve(l)
  }
docs: // ServeTCP makes the handler to listen for request in a given TCP address.
  // It also writes the spec file in the right directory for docker to read.
  // Due to constrains for running Docker in Docker on Windows, data-root directory
  // of docker daemon must be provided. To get default directory, use
  // WindowsDefaultDaemonRootDir() function. On Unix, this parameter is ignored.