这算是一篇读书笔记，留着以后复习看看。
Web Server又称为Http Server，因为它使用HTTP协议和客户端（一般是各种各样的浏览器）进行通信。
什么是HTTP协议呢？
HTTP协议是基于有状态的TCP协议（默认的的TCP端口是80），最早版本的HTTP协议是HTTP/0.9，然后被HTTP/1.0代替了，代替HTTP/1.0的是现在使用的HTTP/1.1，详细介绍可以看RFC（请求注释）文档：http://www.w3.org/Protocols/HTTP/1.1/rfc2616.pdf。在HTTP协议中，总是客户端发起一个请求，服务器端是不会向客户端发起请求的。不管是客户端还是服务器端，都可以随时结束请求。
一个HTTP请求是由3部分组成的，请求行+请求头+请求实体，如下面这样
POST /examples/default.jsp HTTP/1.1 Host: localhost Connection: Keep-Alive Content-Length: 33 Content-Type: application/x-www-form-urlencoded lastName=Franks&firstName=Michael
NOTE:请求头和请求实体之间要有一个空行（如果不包含请求实体，那么请求头结束后也要有一个空行），并且请求实体结束了要有一个空行。这样就是一个合法的HTTP请求了。
NOTE:一个合法的HTTP请求，应该可以没有请求实体，但是请求行和请求头（猜想这个请求头Connection: 是必须的）是不可以少的。
下面用一个例子，通过手动构造HTTP请求，请求baidu服务器端
/** * Created by user on 14-1-11. */ public class TestSocket1 { public static void main(String[] args) throws Exception { //建立连接 Socket socket = new Socket("www.baidu.com", 80); InputStream is = socket.getInputStream(); OutputStream os = socket.getOutputStream(); //发送请求 // //发送请求 方法1 // boolean autoFlush = true; // PrintWriter pw = new PrintWriter(os, autoFlush); // pw.println("GET / HTTP/1.1"); // pw.println("Host: www.baidu.com"); // pw.println("Connection: Close"); // //NOTE: 即使没有请求体，请求头后面的回车换行也是不可以少的 // pw.println(); //发送请求 方法2 String CRLF = " "; StringBuffer requestSb = new StringBuffer(); requestSb.append("GET / HTTP/1.1").append(CRLF) .append("Host: www.baidu.com").append(CRLF) .append("Connection: Close").append(CRLF) .append(CRLF); os.write(requestSb.toString().getBytes()); os.flush(); /* //发送请求 方法3 : 测试，请求头是必须的，请求行也是必须的（至少要有Connection: ） String CRLF = " "; StringBuffer requestSb = new StringBuffer(); requestSb.append("GET / HTTP/1.1").append(CRLF) // .append("Host: www.baidu.com").append(CRLF) .append("Connection: Close").append(CRLF) .append(CRLF); os.write(requestSb.toString().getBytes()); os.flush(); */ //读取响应 BufferedReader br = new BufferedReader(new InputStreamReader(is, "UTF-8")); StringBuffer sb = new StringBuffer(1024 * 8); boolean loop = true; while(loop) { if(br.ready()) { int i = 0; while(i != -1) { i = br.read(); sb.append((char)i); } loop = false; } } System.out.println(sb.toString()); socket.close(); } }
结果如下：
HTTP/1.1 200 OK Date: Sat, 11 Jan 2014 00:11:08 GMT Content-Type: text/html Transfer-Encoding: chunked Connection: Close Vary: Accept-Encoding Set-Cookie: BAIDUID=E89438B4C3C8B9A5D360DA8EF0F30A79:FG=1; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com Set-Cookie: BDSVRTM=0; path=/ Set-Cookie: H_PS_PSSID=4848_4820_4787_1446_4261_4989_4897_4760_4883_4678; path=/; domain=.baidu.com P3P: CP=" OTI DSP COR IVA OUR IND COM " Expires: Sat, 11 Jan 2014 00:10:20 GMT Cache-Control: private Server: BWS/1.1 BDPAGETYPE: 1 BDQID: 0x9626313d91064e78 BDUSERID: 0 3d94 <!DOCTYPE html><!--STATUS OK--><html><head><meta http-equiv="content-type" content="text/html;charset=utf-8"><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 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#e3e3e3;white-space:nowrap;z-index:1;border-bottom-color:#e0e0e0;border-right-color:#ececec;box-shadow:1px 2px 1px rgba(0,0,0,0.072);-webkit-box-shadow:0 2px 2px rgba(0,0,0,0.072);-moz-box-shadow:1px 2px 1px rgba(0,0,0,0.072);-o-box-shadow:0 2px 2px rgba(0,0,0,0.072)}.ws-tips img{vertical-align:middle;width:56px;height:56px;position:absolute;left:10px;top:10px}.ws-d-info{text-align:center;width:144px;height:46px;position:absolute;left:76px;top:15px}.ws-d-label{font-size:14px;font-family:'宋体';color:#666}.ws-d-label span{font-family:arial}#ws-btn{position:absolute;right:8px;top:8px;background:url('http://s1.bdstatic.com/r/www/cache/static/global/img/wsCloseBtn2_4a84c812.png') no-repeat;width:9px;height:9px}#ws-btn:focus{outline:0}.ws-d-info a{margin-top:6px;font:bold 12px/24px "宋体"}</style><script >function h(obj){obj.style.behavior='url(#default#homepage)';var a = obj.setHomePage('http://www.baidu.com/');}</script></head><body><div id="wrapper"><div id="content"><div id="u"><a href="http://www.baidu.com/gaoji/preferences.html" name="tj_setting">搜索设置</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="https://passport.baidu.com/v2/?reg®Type=1&tpl=mn&u=http%3A%2F%2Fwww.baidu.com%2F" target="_blank" name="tj_reg" class="reg">注册</a></div><div id="m"><p id="lg"><img src="http://www.baidu.com/img/bdlogo.gif" 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 name="f" action="/s"><span class="bg s_ipt_wr"><input type="text" name="wd" id="kw" 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="su" 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="mHolder"><div id="mCon"><span>输入法</span></div></span></span><ul id="mMenu"><li><a href="#" name="ime_hw">手写</a></li><li><a href="#" name="ime_py">拼音</a></li><li class="ln"></li><li><a href="#" 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="http://www.baidu.com/more/">更多>></a></span></p><p id="lm"></p></div></div><div id="ftCon"><div id="ftConw"><p ><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="http://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><span id="sekj"><a href="http://anquan.baidu.com/?wenzilian" target="_blank" onmousedown="return ns_c({'fm':'behs','tab':'bdbrwlk','pos':1})">安装百度卫士</a></span></p><p id="lh"><a href="http://e.baidu.com/?refer=888" onmousedown="return ns_c({'fm':'behs','tab':'btlink','pos':2})">加入百度推广</a> | <a onmousedown="return ns_c({'fm':'behs','tab':'tj_bang'})" href="http://top.baidu.com">搜索风云榜</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">©2014 Baidu <a href="/duty/" name="tj_duty">使用百度前必读</a> 京ICP证030173号 <img src="http://www.baidu.com/cache/global/img/gs.gif"></p></div></div></div><script>var bds={se:{},comm : {ishome : 1,sid : 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模仿how tomcat works第一章写的程序，地址：http://download.csdn.net/detail/hx888/6836501
运行效果
