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 @Override 14 public void onClick(View v) 15 { 16 InputStream is = null; 17 HttpURLConnection httpUrlConn = null; 18 try 19 { 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=123 25 sbUrl 26 .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 finally 70 { 71 if(is != null) 72 { 73 try 74 { 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 try 108 { 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 });