Android网络编程原理及HttpURLConnection 用法

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网络通信层次图

TCP报文段格式

建链过程中的“三次握手”

1、SYN(Synchronize Sequence Numbers)是TCP是传输控制协议中的一个标志位。如果该位被置为1，则表示这个报文是一个请求建立连接的报文。
2、ACK(ACKnowledge Character）中文：确认字符。也是TCP是传输控制协议的一个标志位。在数据通信传输中，接收站发给发送站的一种传输控制字符。它表示确认发来的数据已经接受无误。是一个用于确认的报文。

关闭链路的四次握手

1、FIN(finish) 结束，没有更多的数据发送

Http请求协议

GET /img/iknow/msg/msg.gif HTTP/1.1
Accept: */*
Referer: http://zhidao.baidu.com/
Accept-Language: zh-CN
User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; Trident/4.0; qdesk 2.5.1277.202; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; Tablet PC 2.0; .NET4.0C)
Accept-Encoding: gzip, deflate
Host: img.baidu.com
Connection: Keep-Alive

Http响应

HTTP/1.1 200 OK
Content-Type: image/gif
ETag: "1068122120"
Accept-Ranges: bytes
Last-Modified: Mon, 19 Dec 2011 08:00:44 GMT
Expires: Wed, 13 Jul 2022 12:27:55 GMT
Cache-Control: max-age=311040000
Content-Length: 1141
Date: Mon, 03 Sep 2012 12:27:55 GMT
Server: BWS/1.0

-----------------------------------------------------------------

HTTP/1.1 状态码错误信息
Content-Type：（类型）
Content-length：（包体长度）

HttpURLConnection Get请求

 1     /** 2      * 1、android模拟器（simulator）把它自己作为了localhost，也就是说，代码中使用localhost或者127.0.0.1来访问， 3      *          都是访问模拟器自己！ 4      * 2、如果想在模拟器simulator上面访问你的电脑，那么就使用android内置的IP 10.0.2.2 ，  5      *    10.0.2.2 是模拟器设置的特定ip，是你的电脑的别名alias 6      * 3、记住，在模拟器上用10.0.2.2访问你的电脑本机 7      */ 8     private final String baseUrl = "http://10.0.2.2:8080/WebProj/main.jsp"; 9     10     //HttpURLConnection Get请求11      btnHttpURLConnection_Get.setOnClickListener(new OnClickListener()12      {13          @Override14          public void onClick(View v)15          {16              InputStream is = null;17              HttpURLConnection httpUrlConn = null;18              try19              {20                  String strAccountNumber = etAccountNumber.getText().toString();21                  String strPwd = etPwd.getText().toString();22                  StringBuffer sbUrl = new StringBuffer();23  24                  //http://10.0.2.2:8080/WebProj/main.jsp?textAccountNumber=abc&textPwd=12325                  sbUrl26                      .append(baseUrl)27                      .append("?textAccountNumber=")28                      //注意如果参数是中文，要做以下处理29                      .append(URLEncoder.encode(strAccountNumber, "utf-8"))30                      .append("&textPwd=")31                      .append(strPwd);32  33                  URL url = new URL(sbUrl.toString());34                  //打开连接35                  httpUrlConn = (HttpURLConnection) url.openConnection();36                  //获取连接状态37                  int rc = httpUrlConn.getResponseCode();38                  39                  //连接成功40                  if(rc == HttpURLConnection.HTTP_OK)41                  {42                      //获取数据，先得到输入流43                      is = httpUrlConn.getInputStream();44                      45                      BufferedReader buffer = new BufferedReader(new InputStreamReader(is,"gbk"));46                      String inputLine = null;47                      StringBuffer sbContent = new StringBuffer();48  49                      while ((inputLine = buffer.readLine()) != null)50                      {51                          sbContent.append(inputLine + "\n");52                      }                53                      54                      //获取到的内容转换成 GBK 编码，防止中文乱码55                      //String strContent = new String(sbContent.toString().getBytes("iso-8859-1"), "gbk");56                      tvContent.setText(sbContent.toString());57                      buffer.close();58                      buffer = null;59                  }60              }61              catch (MalformedURLException e)62              {63                  e.printStackTrace();64              }65              catch (IOException e)66              {67                  e.printStackTrace();68              }69              finally70              {71                  if(is != null)72                  {73                      try74                      {75                          is.close();76                          is = null;77                      }78                      catch (IOException e)79                      {80                          e.printStackTrace();81                      }82                  }83                  84                  if(httpUrlConn != null)85                  {86                      //关闭连接87                      httpUrlConn.disconnect();88                      httpUrlConn = null;89                  }90              }91          }92      });

HttpURLConnection Post请求

  1     /**  2      * 1、android模拟器（simulator）把它自己作为了localhost，也就是说，代码中使用localhost或者127.0.0.1来访问，  3      *          都是访问模拟器自己！  4      * 2、如果想在模拟器simulator上面访问你的电脑，那么就使用android内置的IP 10.0.2.2 ，   5      *    10.0.2.2 是模拟器设置的特定ip，是你的电脑的别名alias  6      * 3、记住，在模拟器上用10.0.2.2访问你的电脑本机  7      */  8     private final String baseUrl = "http://10.0.2.2:8080/WebProj/main.jsp";  9      10      11     //HttpURLConnection Post请求 12     btnHttpURLConnection_Post.setOnClickListener(new OnClickListener() 13     { 14         @Override 15         public void onClick(View v) 16         { 17             DataOutputStream dos = null; 18             InputStream is = null; 19             HttpURLConnection httpUrlConn = null; 20             try 21             { 22                 String strAccountNumber = etAccountNumber.getText().toString(); 23                 String strPwd = etPwd.getText().toString(); 24                 URL url = new URL(baseUrl); 25                 //获取一个连接 26                 httpUrlConn = (HttpURLConnection) url.openConnection(); 27                 //允许连接输出 28                 httpUrlConn.setDoOutput(true); 29                 //允许连接输入 30                 httpUrlConn.setDoInput(true); 31                 //设置以 POST 方式发送请求 32                 httpUrlConn.setRequestMethod("POST"); 33                 //设置 POST 请求不能使用缓存 34                 httpUrlConn.setUseCaches(false); 35                 //设置这个连接是否可以重定向 36                 httpUrlConn.setInstanceFollowRedirects(true); 37                 //设置请求头的域的值 38                 //配置本连接的 CONTENT_TYPE 为 application/x-www-form-urlencoded 39                 httpUrlConn.setRequestProperty(HTTP.CONTENT_TYPE, URLEncodedUtils.CONTENT_TYPE); 40                 //连接，所有的配置信息要 connect() 方法前完成，httpUrlConn.getOutputStream 会隐含地进行 connect 41                 httpUrlConn.connect(); 42                 //构造请求包体的内容 43                 StringBuffer sbParam = new StringBuffer(); 44                 //textAccountNumber=abc&textPwd=123 45                 sbParam 46                     .append("textAccountNumber=") 47                     .append(URLEncoder.encode(strAccountNumber, "gbk")) 48                     .append("&textPwd=") 49                     .append(URLEncoder.encode(strPwd, "gbk")); 50                 //获取连接的输出流 51                 dos = new DataOutputStream(httpUrlConn.getOutputStream()); 52                 //将参数写入输出流 53                 dos.writeBytes(sbParam.toString()); 54                 dos.flush(); 55                 dos.close(); 56                 dos = null;                     57                  58                  59                 //获取连接状态，当执行 getInputStream() 时，才将输出流中的数据发送出去 60                 int rc = httpUrlConn.getResponseCode();//HttpURLConnection.HTTP_OK; 61                 System.out.println("httpUrlConn.getResponseCode()=" + rc); 62                 //连接成功 63                 if(rc == HttpURLConnection.HTTP_OK) 64                 { 65                     //获取数据 66                     is = httpUrlConn.getInputStream(); 67                      68                     BufferedReader buffer = new BufferedReader(new InputStreamReader(is,"gbk")); 69                     String inputLine = null; 70                     StringBuffer sbContent = new StringBuffer(); 71                      72                     while ((inputLine = buffer.readLine()) != null) 73                     { 74                         sbContent.append(inputLine + "\n"); 75                     } 76                      77                     tvContent.setText(sbContent.toString()); 78                     buffer.close(); 79                     buffer = null; 80                 } 81             } 82             catch (MalformedURLException e) 83             { 84                 e.printStackTrace(); 85             } 86             catch (IOException e) 87             { 88                 e.printStackTrace(); 89             } 90             finally 91             { 92                 if(dos != null) 93                 { 94                     try 95                     { 96                         dos.close(); 97                         dos = null; 98                     } 99                     catch (IOException e)100                     {101                         e.printStackTrace();102                     }103                 }104             105                 if(is != null)106                 {107                     try108                     {109                         is.close();110                         is = null;111                     }112                     catch (IOException e)113                     {114                         e.printStackTrace();115                     }116                 }117                 118                 if(httpUrlConn != null)119                 {120                     //关闭连接121                     httpUrlConn.disconnect();122                     httpUrlConn = null;123                 }124             }125         }126     });