这里主要是玩一下http协议，查看http的header。
1、输入命令telnet访问百度
# telnet www.baidu.com 80
Trying 220.181.112.244...
Connected to www.baidu.com.
Escape character is '^]'.
2、输入请求头，这里有时间限制，很快会自动断开，所以提前写好粘贴进去
GET /index.html HTTP/1.1
Host: www.baidu.com
3、两次回车，返回响应头
HTTP/1.1 200 OK
Date: Sun, 17 Sep 2017 09:31:07 GMT
Content-Type: text/html
Content-Length: 14613
Last-Modified: Thu, 14 Sep 2017 03:04:00 GMT
Connection: Keep-Alive
Vary: Accept-Encoding
Set-Cookie: BAIDUID=B0BE15AB9B826700DABA32CFEA847004:FG=1; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com
Set-Cookie: BIDUPSID=B0BE15AB9B826700DABA32CFEA847004; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com
Set-Cookie: PSTM=1505640667; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com
P3P: CP=" OTI DSP COR IVA OUR IND COM "
Server: BWS/1.1
X-UA-Compatible: IE=Edge,chrome=1
Pragma: no-cache
Cache-control: no-cache
Accept-Ranges: bytes
<!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>
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<body link="#0000cc"><div id="wrapper" style="display:none;"><div id="u"><a href="//www.baidu.com/gaoji/preferences.html" onmousedown="return user_c({'fm':'set','tab':'setting','login':'0'})">搜索设置</a>|<a id="btop" href="/" onmousedown="return user_c({'fm':'set','tab':'index','login':'0'})">百度首页</a>|<a id="lb" href="https://passport.baidu.com/v2/?login&tpl=mn&u=http%3A%2F%2Fwww.baidu.com%2F" onclick="return false;" onmousedown="return user_c({'fm':'set','tab':'login'})">登录</a><a href="https://passport.baidu.com/v2/?reg®Type=1&tpl=mn&u=http%3A%2F%2Fwww.baidu.com%2F" onmousedown="return user_c({'fm':'set','tab':'reg'})" target="_blank" class="reg">注册</a></div><div id="head"><div class="s_nav"><a href="/" class="s_logo" onmousedown="return c({'fm':'tab','tab':'logo'})"><img src="//www.baidu.com/img/baidu_jgylogo3.gif" width="117" height="38" border="0" alt="到百度首页" title="到百度首页"></a><div class="s_tab" id="s_tab"><a href="http://news.baidu.com/ns?cl=2&rn=20&tn=news&word=" wdfield="word" onmousedown="return c({'fm':'tab','tab':'news'})">新闻</a>　<b>网页</b>　<a href="http://tieba.baidu.com/f?kw=&fr=wwwt" wdfield="kw" onmousedown="return c({'fm':'tab','tab':'tieba'})">贴吧</a>　<a href="http://zhidao.baidu.com/q?ct=17&pn=0&tn=ikaslist&rn=10&word=&fr=wwwt" wdfield="word" onmousedown="return c({'fm':'tab','tab':'zhidao'})">知道</a>　<a href="http://music.baidu.com/search?fr=ps&key=" wdfield="key" onmousedown="return c({'fm':'tab','tab':'music'})">音乐</a>　<a href="http://image.baidu.com/i?tn=baiduimage&ps=1&ct=201326592&lm=-1&cl=2&nc=1&word=" wdfield="word" onmousedown="return c({'fm':'tab','tab':'pic'})">图片</a>　<a href="http://v.baidu.com/v?ct=301989888&rn=20&pn=0&db=0&s=25&word=" wdfield="word" onmousedown="return c({'fm':'tab','tab':'video'})">视频</a>　<a href="http://map.baidu.com/m?word=&fr=ps01000" wdfield="word" onmousedown="return c({'fm':'tab','tab':'map'})">地图</a>　<a href="http://wenku.baidu.com/search?word=&lm=0&od=0" wdfield="word" onmousedown="return c({'fm':'tab','tab':'wenku'})">文库</a>　<a href="//www.baidu.com/more/" onmousedown="return c({'fm':'tab','tab':'more'})">更多»</a></div></div><form id="form" name="f" action="/s" class="fm" ><input type="hidden" name="ie" value="utf-8"><input type="hidden" name="f" value="8"><input type="hidden" name="rsv_bp" value="1"><span class="bg s_ipt_wr"><input name="wd" id="kw" class="s_ipt" value="" maxlength="100"></span><span class="bg s_btn_wr"><input type="submit" id="su" value="百度一下" class="bg s_btn" onmousedown="this.className='bg s_btn s_btn_h'" onmouseout="this.className='bg s_btn'"></span><span class="tools"><span id="mHolder"><div id="mCon"><span>输入法</span></div><ul id="mMenu"><li><a href="javascript:;" name="ime_hw">手写</a></li><li><a href="javascript:;" name="ime_py">拼音</a></li><li class="ln"></li><li><a href="javascript:;" name="ime_cl">关闭</a></li></ul></span><span class="shouji"><strong>推荐 : </strong><a href="http://w.x.baidu.com/go/mini/8/10000020" onmousedown="return ns_c({'fm':'behs','tab':'bdbrowser'})">百度浏览器，打开网页快2秒！</a></span></span></form></div><div id="content"><div id="u1"><a href="http://news.baidu.com" name="tj_trnews" class="mnav">新闻</a><a href="http://www.hao123.com" name="tj_trhao123" class="mnav">hao123</a><a href="http://map.baidu.com" name="tj_trmap" class="mnav">地图</a><a href="http://v.baidu.com" name="tj_trvideo" class="mnav">视频</a><a href="http://tieba.baidu.com" name="tj_trtieba" class="mnav">贴吧</a><a href="https://passport.baidu.com/v2/?login&tpl=mn&u=http%3A%2F%2Fwww.baidu.com%2F" name="tj_login" id="lb" onclick="return false;">登录</a><a href="//www.baidu.com/gaoji/preferences.html" name="tj_settingicon" id="pf">设置</a><a href="//www.baidu.com/more/" name="tj_briicon" id="bri">更多产品</a></div><div id="m"><p id="lg"><img src="//www.baidu.com/img/bd_logo.png" width="270" height="129"></p><p id="nv"><a href="http://news.baidu.com">新 闻</a> <b>网 页</b> <a href="http://tieba.baidu.com">贴 吧</a> <a href="http://zhidao.baidu.com">知 道</a> <a href="http://music.baidu.com">音 乐</a> <a href="http://image.baidu.com">图 片</a> <a href="http://v.baidu.com">视 频</a> <a href="http://map.baidu.com">地 图</a></p><div id="fm"><form id="form1" name="f1" action="/s" class="fm"><span class="bg s_ipt_wr"><input type="text" name="wd" id="kw1" maxlength="100" class="s_ipt"></span><input type="hidden" name="rsv_bp" value="0"><input type=hidden name=ch value=""><input type=hidden name=tn value="baidu"><input type=hidden name=bar value=""><input type="hidden" name="rsv_spt" value="3"><input type="hidden" name="ie" value="utf-8"><span class="bg s_btn_wr"><input type="submit" value="百度一下" id="su1" class="bg s_btn" onmousedown="this.className='bg s_btn s_btn_h'" onmouseout="this.className='bg s_btn'"></span></form><span class="tools"><span id="mHolder1"><div id="mCon1"><span>输入法</span></div></span></span><ul id="mMenu1"><div class="mMenu1-tip-arrow"><em></em><ins></ins></div><li><a href="javascript:;" name="ime_hw">手写</a></li><li><a href="javascript:;" name="ime_py">拼音</a></li><li class="ln"></li><li><a href="javascript:;" name="ime_cl">关闭</a></li></ul></div><p id="lk"><a href="http://baike.baidu.com">百科</a> <a href="http://wenku.baidu.com">文库</a> <a href="http://www.hao123.com">hao123</a><span> | <a href="//www.baidu.com/more/">更多>></a></span></p><p id="lm"></p></div></div><div id="ftCon"><div id="ftConw"><p id="lh"><a id="seth" onClick="h(this)" href="/" onmousedown="return ns_c({'fm':'behs','tab':'homepage','pos':0})">把百度设为主页</a><a id="setf" href="//www.baidu.com/cache/sethelp/index.html" onmousedown="return ns_c({'fm':'behs','tab':'favorites','pos':0})" target="_blank">把百度设为主页</a><a onmousedown="return ns_c({'fm':'behs','tab':'tj_about'})" href="http://home.baidu.com">关于百度</a><a onmousedown="return ns_c({'fm':'behs','tab':'tj_about_en'})" href="http://ir.baidu.com">About Baidu</a></p><p id="cp">©2017 Baidu <a href="/duty/" name="tj_duty">使用百度前必读</a> 京ICP证030173号 <img 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