为什么浏览器会阻塞一些端口?

I'm playing around with websockets and it appears, that all browsers with native websocket support I tested with (Safari, Chrome) block some ports. If I try to connect to my server over port 80, everyting works fine. If I try other ports, like 81, 82 or 1000, the connection is prematurely closed because there's nothing on the other end. That's the expected behaviour and it works beautifully.I'm playing around with websockets and it appea