about Failed to connect to test server on http://csswg.test:34543

Hi, I am following here https://github.com/w3c/csswg-test Running the Tests
to run css test on my local machine.

But it failed when ./serve, the console outputs:
"INFO:web-platform-tests:Starting http server on csswg.test:34543
CRITICAL:web-platform-tests:Failed to connect to test server on
http://csswg.test:34543 You may need to edit /etc/hosts or similar
"

The hosts file:
abc@abc-ubuntu:~/w3c$ cat /etc/hosts
127.0.0.1 localhost
127.0.1.1 abc-ubuntu
127.0.0.1 csswg.test
127.0.0.1 www.csswg.test
127.0.0.1 www1.csswg.test
127.0.0.1 www2.csswg.test
127.0.0.1 xn--n8j6ds53lwwkrqhv28a.csswg.test
127.0.0.1 xn--lve-6lad.csswg.test
0.0.0.0 nonexistent-origin.csswg.test


The config.json file:
abc@abc-ubuntu:~/w3c/csswg-test$ cat config.json {"host": "csswg.test",
"doc_root": null, "ws_doc_root": null, "external_host": null,
"ports":{"http":[1234, "auto"], "https":[8443], "ws":["auto"],
"wss":["auto"]}, "check_subdomains": true, "log_level":"debug",
"bind_hostname": true, "ssl": {"type": "openssl", "encrypt_after_connect":
false, "openssl": { "openssl_binary": "/usr/bin/openssl", "base_path":
"_certs", "force_regenerate": false, "base_conf_path": null },
"pregenerated": { "host_key_path": null, "host_cert_path": null }, "none":
{} } }



-- 
NaCl!