Are you sometimes in need of a network diagnostic tool to verify if your Internet Service Provider, or company network, or home network is blocking outgoing connections to certain port numbers? No problem. Walk to open.zorinaq.com. All 65k TCP ports, from 1 to 65535, are open on this web server. It is a useful network diagnostic tool.
To test from a browser, add colon(:) followed by the port number after the hostname. For example, http://open.zorinaq.com:80 tests the default HTTP port. Try other common ports: 8000, 8080, 443. However be aware that some browsers block ports such as 1, 7, 9, 11, 13, 15, 17, ..., 65535. For ports blocked by Google Chrome, see kRestrictedPorts in port_util.cc. For ports blocked by Mozilla Firefox, see this page.
To test from a Unix shell:
$ curl open.zorinaq.com:1234 Yep, port 1234 is open. <a href="http://blog.zorinaq.com/?e=60">About...</a>
$ telnet open.zorinaq.com 1234