env

telnet 和 nc

telnet

macOS 10.13 去掉了telnet。
安装， brew install telnet
简单使用示例，

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$ telnet www.baidu.com 80
Trying 61.135.169.121...
Connected to www.a.shifen.com.
Escape character is '^]'.

输入

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GET / HTTP/1.1
Host: www.baidu.com

Response

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HTTP/1.1 200 OK
Accept-Ranges: bytes
Cache-Control: no-cache
Connection: Keep-Alive
Content-Length: 14615
Content-Type: text/html
Date: Mon, 18 Jun 2018 16:01:48 GMT
Last-Modified: Mon, 11 Jun 2018 11:19:00 GMT
P3p: CP=" OTI DSP COR IVA OUR IND COM "
Pragma: no-cache
Server: BWS/1.1
Set-Cookie: BAIDUID=47DF48A1AE3963EA34DF3B898FF8AAC3:FG=1; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com
Set-Cookie: BIDUPSID=47DF48A1AE3963EA34DF3B898FF8AAC3; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com
Set-Cookie: PSTM=1529337708; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com
Vary: Accept-Encoding
X-Ua-Compatible: IE=Edge,chrome=1

<!DOCTYPE html><!--STATUS OK-->
<html>
<head>
	<meta http-equiv="content-type" content="text/html;charset=utf-8">
	<meta http-equiv="X-UA-Compatible" content="IE=Edge">
	<link rel="dns-prefetch" href="//s1.bdstatic.com"/>
	<link rel="dns-prefetch" href="//t1.baidu.com"/>
	<link rel="dns-prefetch" href="//t2.baidu.com"/>
	<link rel="dns-prefetch" href="//t3.baidu.com"/>
	<link rel="dns-prefetch" href="//t10.baidu.com"/>
	<link rel="dns-prefetch" href="//t11.baidu.com"/>
	<link rel="dns-prefetch" href="//t12.baidu.com"/>
	<link rel="dns-prefetch" href="//b1.bdstatic.com"/>
	<title>百度一下，你就知道</title>
（以下省略）
……
……
……

nc

即：netcat

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$ nc www.baidu.com 80

输入

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GET / HTTP/1.1
Host: www.baidu.com

Response也是一个网页。

上述示例中的以下输入，

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GET / HTTP/1.1
Host: www.baidu.com

和浏览器访问时的Request是一样的，可以用浏览器访问网站，Chrome开发者工具 - Network - Headers - Request Headers - view source