#发起一个http请求。
$ curl -o /dev/null -v http://example.com
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0* Host example.com:80 was resolved.
* IPv6: 2606:2800:21f:cb07:6820:80da:af6b:8b2c
* IPv4: 93.184.215.14
* Trying 93.184.215.14:80...
* Trying [2606:2800:21f:cb07:6820:80da:af6b:8b2c]:80...
* Immediate connect fail for 2606:2800:21f:cb07:6820:80da:af6b:8b2c: Network is unreachable
* Connected to example.com (93.184.215.14) port 80
> GET / HTTP/1.1
> Host: example.com
> User-Agent: curl/8.5.0
> Accept: */*
>
< HTTP/1.1 200 OK
< Accept-Ranges: bytes
< Age: 422312
< Cache-Control: max-age=604800
< Content-Type: text/html; charset=UTF-8
< Date: Tue, 19 Nov 2024 16:01:26 GMT
< Etag: "3147526947"
< Expires: Tue, 26 Nov 2024 16:01:26 GMT
< Last-Modified: Thu, 17 Oct 2019 07:18:26 GMT
< Server: ECAcc (sed/58C9)
< Vary: Accept-Encoding
< X-Cache: HIT
< Content-Length: 1256
<
{ [1256 bytes data]
100 1256 100 1256 0 0 2600 0 --:--:-- --:--:-- --:--:-- 2600
* Connection #0 to host example.com left intact
1、首先是域名解析：
* Host example.com:80 was resolved.
* IPv6: 2606:2800:21f:cb07:6820:80da:af6b:8b2c
* IPv4: 93.184.215.14
2、建立TCP链接
* Trying 93.184.215.14:80...
* Trying [2606:2800:21f:cb07:6820:80da:af6b:8b2c]:80...
* Immediate connect fail for 2606:2800:21f:cb07:6820:80da:af6b:8b2c: Network is unreachable
* Connected to example.com (93.184.215.14) port 80
其中IPV6不可达 ，IPV4 正常
3、开始发送http请求
> GET / HTTP/1.1
> Host: example.com
> User-Agent: curl/8.5.0
> Accept: */*
4、服务器响应
< HTTP/1.1 200 OK
< Accept-Ranges: bytes
< Age: 422312
< Cache-Control: max-age=604800
< Content-Type: text/html; charset=UTF-8
< Date: Tue, 19 Nov 2024 16:01:26 GMT
< Etag: "3147526947"
< Expires: Tue, 26 Nov 2024 16:01:26 GMT
< Last-Modified: Thu, 17 Oct 2019 07:18:26 GMT
< Server: ECAcc (sed/58C9)
< Vary: Accept-Encoding
< X-Cache: HIT
< Content-Length: 1256
<
{ [1256 bytes data]
100 1256 100 1256 0 0 2600 0 --:--:-- --:--:-- --:--:-- 2600
* Connection #0 to host example.com left intact
