端口80在我的ISP上被阻止，所以我的浏览器仍然可以工作？ [英] Port 80 blocked on my ISP so how my browser still works?

问题描述

我知道当我请求example.com时，我的浏览器实际上是对example.com:80的侮辱。但是我的ISP会阻止80端口监听，所以如果端口80被阻止，我如何收到请求的响应？它应该不起作用，不是吗？

I know that when I request example.com my browser actually deafults to example.com:80 . However my ISP block the 80 port from listening so HOW do I receive the responses from my requests if the port 80 is blocked? It should not work, isnt?

推荐答案

当您发出HTTP请求（实际上是任何TCP请求）时，有两个涉及的港口。目的地上有端口80（在您的情况下，example.com），您的计算机上有一个端口;此端口称为源端口，因为您的计算机是请求的来源。

When you make an HTTP request (in fact, any TCP request), there are two ports involved. There is port 80 on the destination (in your case, "example.com"), and there is a port on your computer; this port is called the "source port" since your computer is the source of the request.

通常，您的计算机将选择超过1,000的随机端口号（例如， 3,135或45,978），因为低编号的端口很容易被记住（和阻塞），并且通常用于托管服务（例如端口80上的网站）。因为源端口是由您的计算机创建的，目的是在端口80上与example.com通信，所以它不会打开很长时间（只需足够长的时间来完成它的工作）。这些有时被称为短暂的端口;请参阅 http://en.wikipedia.org/wiki/Ephemeral_port

Typically, your computer will pick a random port number over 1,000 (for example, 3,135 or 45,978), since low-numbered ports are easily remembered (and blocked) and are typically used for hosting services (such as a web site on port 80). Because the source port is created by your computer for the purpose of talking to example.com on port 80, it won't be open very long (just long enough to do its job). These are sometimes called "ephemeral ports"; see http://en.wikipedia.org/wiki/Ephemeral_port

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