什么是Socket?
所謂Socket通常也稱作“套接字”，用於描述IP地址和端口，是一個通信連的句柄，應用程序通常通過“套接字”向網絡發送請求或者應答網絡請求，它就是網絡通信過程中端點的抽象表示。它主要包括以下兩個協議：
TCP (Transmission Control Protocol 傳輸控制協議)：傳輸控制協議,提供的是面向連接、可靠的字節流服務。當客戶和服務器彼此交換數據前，必須先在雙方之間建立一個TCP連接，之后才能傳輸數據。TCP提供超時重發，丟棄重復數據，檢驗數據，流量控制等功能，保證數據能從一端傳到另一端。
UDP (User Datagram Protocl 用戶數據報協議)：用戶數據報協議，是一個簡單的面向數據報的運輸層協議。UDP不提供可靠性，它只是把應用程序傳給IP層的數據報發送出去，但是並不能保證它們能到達目的地。由於UDP在傳輸數據報前不用在客戶和服務器之間建立一個連接，且沒有超時重發等機制，故而傳輸速度很快。
詳細解說如下:
TCP傳輸和UDP不一樣，TCP傳輸是流式的，必須先建立連接，然后數據流沿已連接的線路(虛電路)傳輸。因此TCP的數據流不會像UDP數據報一樣，每個數據報都要包含目標地址和端口，因為每個數據報要單獨路由。TCP傳輸則只需要在建立連接時指定目標地址和端口就可以了。
形象的講，TCP就像打電話，UDP就像發電報。宏觀上來看UDP是不分客戶端和服務端的。通信雙方是平等的。微觀上來講只相對一個報文，發送端是客戶端，監聽端是服務端。發送端把數據報發給路由器就像把電報發給了郵局，后面的事情就是發送者無法控制，也無從知曉的了。所以說是不可靠的，可能會出現報文丟失而無從知曉。就像每張電報都要有收件人一樣，每個數據報都要有目的地址和端口。
而TCP每次連接都是分客戶端和服務端的。連接的發起者(相當與撥號打電話的人)是客戶端，監聽者(相當於在電話邊等着接電話的人)是服務端。發起者指定要連接的服務器地址和端口(相當於撥號)，監聽者通過和發起者三次握手建立連接(相當於聽到電話響去接電話)。建立連接后雙方可以互相發送和接受數據(打電話)。
Java如何操作Socket?
值得一提的是，Java分別為TCP和UDP提供了相應的類,TCP是java.net中提供了兩個類Socket和ServerSocket，分別用來表示雙向連接的客戶端和服務端。這是兩個封裝得非常好的類，使用起來很方便！UDP是java.net.DatagramSocket.
127.0.0.1是回路地址,用於測試,相當於localhost本機地址,沒有網卡,不設DNS都可以訪問,端口地址在0~65535之間,其中0~1023之間的端口是用於一些知名的網絡服務和應用,用戶的普通網絡應用程序應該使用1024以上的端口.
Socket通信模型如下：
如果大家對Java Socket編程還有模糊的地方抓緊溫習(http://blog.csdn.net/shimiso/article/details/8529941),本文不在此贅述,下面我們以最常用的TCP協議舉例:
服務器，使用ServerSocket監聽指定的端口，端口可以隨意指定（由於1024以下的端口通常屬於保留端口，在一些操作系統中不可以隨意使用，所以建議使用大於1024的端口），等待客戶連接請求，客戶連接后，會話產生；在完成會話后，關閉連接。
客戶端，使用Java socket通信對網絡上某一個服務器的某一個端口發出連接請求，一旦連接成功，打開會話；會話完成后，關閉Socket。客戶端不需要指定打開的端口，通常臨時的、動態的分配一個1024以上的端口。
TCP網絡連接模型：
Android客戶端程序代分析:
UploadActivity.java package com.android.upload; import java.io.File; import java.io.OutputStream; import java.io.PushbackInputStream; import java.io.RandomAccessFile; import java.net.Socket; import android.app.Activity; import android.os.Bundle; import android.os.Environment; import android.os.Handler; import android.os.Message; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.ProgressBar; import android.widget.TextView; import android.widget.Toast; import com.android.service.UploadLogService; import com.android.socket.utils.StreamTool; public class UploadActivity extends Activity { private EditText filenameText; private TextView resulView; private ProgressBar uploadbar; private UploadLogService logService; private boolean start=true; private Handler handler = new Handler(){ @Override public void handleMessage(Message msg) { int length = msg.getData().getInt("size"); uploadbar.setProgress(length); float num = (float)uploadbar.getProgress()/(float)uploadbar.getMax(); int result = (int)(num * 100); resulView.setText(result+ "%"); if(uploadbar.getProgress()==uploadbar.getMax()){ Toast.makeText(UploadActivity.this, R.string.success, 1).show(); } } }; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); logService = new UploadLogService(this); filenameText = (EditText)this.findViewById(R.id.filename); uploadbar = (ProgressBar) this.findViewById(R.id.uploadbar); resulView = (TextView)this.findViewById(R.id.result); Button button =(Button)this.findViewById(R.id.button); Button button1 =(Button)this.findViewById(R.id.stop); button1 .setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { start=false; } }); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { start=true; String filename = filenameText.getText().toString(); if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){ File uploadFile = new File(Environment.getExternalStorageDirectory(), filename); if(uploadFile.exists()){ uploadFile(uploadFile); }else{ Toast.makeText(UploadActivity.this, R.string.filenotexsit, 1).show(); } }else{ Toast.makeText(UploadActivity.this, R.string.sdcarderror, 1).show(); } } }); } /** * 上傳文件 * @param uploadFile */ private void uploadFile(final File uploadFile) { new Thread(new Runnable() { @Override public void run() { try { uploadbar.setMax((int)uploadFile.length()); String souceid = logService.getBindId(uploadFile); String head = "Content-Length="+ uploadFile.length() + ";filename="+ uploadFile.getName() + ";sourceid="+ (souceid==null? "" : souceid)+"\r\n"; Socket socket = new Socket("192.168.1.78",7878); OutputStream outStream = socket.getOutputStream(); outStream.write(head.getBytes()); PushbackInputStream inStream = new PushbackInputStream(socket.getInputStream()); String response = StreamTool.readLine(inStream); String[] items = response.split(";"); String responseid = items[0].substring(items[0].indexOf("=")+1); String position = items[1].substring(items[1].indexOf("=")+1); if(souceid==null){//代表原來沒有上傳過此文件，往數據庫添加一條綁定記錄 logService.save(responseid, uploadFile); } RandomAccessFile fileOutStream = new RandomAccessFile(uploadFile, "r"); fileOutStream.seek(Integer.valueOf(position)); byte[] buffer = new byte[1024]; int len = -1; int length = Integer.valueOf(position); while(start&&(len = fileOutStream.read(buffer)) != -1){ outStream.write(buffer, 0, len); length += len; Message msg = new Message(); msg.getData().putInt("size", length); handler.sendMessage(msg); } fileOutStream.close(); outStream.close(); inStream.close(); socket.close(); if(length==uploadFile.length()) logService.delete(uploadFile); } catch (Exception e) { e.printStackTrace(); } } }).start(); } } StreamTool.java package com.android.socket.utils; import java.io.ByteArrayOutputStream; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.PushbackInputStream; public class StreamTool { public static void save(File file, byte[] data) throws Exception { FileOutputStream outStream = new FileOutputStream(file); outStream.write(data); outStream.close(); } public static String readLine(PushbackInputStream in) throws IOException { char buf[] = new char[128]; int room = buf.length; int offset = 0; int c; loop: while (true) { switch (c = in.read()) { case -1: case '\n': break loop; case '\r': int c2 = in.read(); if ((c2 != '\n') && (c2 != -1)) in.unread(c2); break loop; default: if (--room < 0) { char[] lineBuffer = buf; buf = new char[offset + 128]; room = buf.length - offset - 1; System.arraycopy(lineBuffer, 0, buf, 0, offset); } buf[offset++] = (char) c; break; } } if ((c == -1) && (offset == 0)) return null; return String.copyValueOf(buf, 0, offset); } /** * 讀取流 * @param inStream * @return 字節數組 * @throws Exception */ public static byte[] readStream(InputStream inStream) throws Exception{ ByteArrayOutputStream outSteam = new ByteArrayOutputStream(); byte[] buffer = new byte[1024]; int len = -1; while( (len=inStream.read(buffer)) != -1){ outSteam.write(buffer, 0, len); } outSteam.close(); inStream.close(); return outSteam.toByteArray(); } } UploadLogService.java package com.android.service; import java.io.File; import android.content.Context; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; public class UploadLogService { private DBOpenHelper dbOpenHelper; public UploadLogService(Context context){ this.dbOpenHelper = new DBOpenHelper(context); } public void save(String sourceid, File uploadFile){ SQLiteDatabase db = dbOpenHelper.getWritableDatabase(); db.execSQL("insert into uploadlog(uploadfilepath, sourceid) values(?,?)", new Object[]{uploadFile.getAbsolutePath(),sourceid}); } public void delete(File uploadFile){ SQLiteDatabase db = dbOpenHelper.getWritableDatabase(); db.execSQL("delete from uploadlog where uploadfilepath=?", new Object[]{uploadFile.getAbsolutePath()}); } public String getBindId(File uploadFile){ SQLiteDatabase db = dbOpenHelper.getReadableDatabase(); Cursor cursor = db.rawQuery("select sourceid from uploadlog where uploadfilepath=?", new String[]{uploadFile.getAbsolutePath()}); if(cursor.moveToFirst()){ return cursor.getString(0); } return null; } } DBOpenHelper.java package com.android.service; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; public class DBOpenHelper extends SQLiteOpenHelper { public DBOpenHelper(Context context) { super(context, "upload.db", null, 1); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL("CREATE TABLE uploadlog (_id integer primary key autoincrement, uploadfilepath varchar(100), sourceid varchar(10))"); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { db.execSQL("DROP TABLE IF EXISTS uploadlog"); onCreate(db); } } main.xml <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/filename" /> <EditText android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="022.jpg" android:id="@+id/filename" /> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/button" android:id="@+id/button" /> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="暫停" android:id="@+id/stop" /> <ProgressBar android:layout_width="fill_parent" android:layout_height="20px" style="?android:attr/progressBarStyleHorizontal" android:id="@+id/uploadbar" /> <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:gravity="center" android:id="@+id/result" /> </LinearLayout> AndroidManifest.xml <?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.android.upload" android:versionCode="1" android:versionName="1.0" > <uses-sdk android:minSdkVersion="8" /> <application android:icon="@drawable/ic_launcher" android:label="@string/app_name" > <activity android:name=".UploadActivity" android:label="@string/app_name" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> <!-- 訪問網絡的權限 --> <uses-permission android:name="android.permission.INTERNET"/> <!-- 在SDCard中創建與刪除文件權限 --> <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/> <!-- 往SDCard寫入數據權限 --> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/> </manifest>
Java服務端:
SocketServer.javapackage com.android.socket.server; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.OutputStream; import java.io.PushbackInputStream; import java.io.RandomAccessFile; import java.net.ServerSocket; import java.net.Socket; import java.text.SimpleDateFormat; import java.util.Date; import java.util.HashMap; import java.util.Map; import java.util.Properties; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import com.android.socket.utils.StreamTool; public class SocketServer { private String uploadPath="D:/uploadFile/"; private ExecutorService executorService;// 線程池 private ServerSocket ss = null; private int port;// 監聽端口 private boolean quit;// 是否退出 private Map<Long, FileLog> datas = new HashMap<Long, FileLog>();// 存放斷點數據，最好改為數據庫存放 public SocketServer(int port) { this.port = port; // 初始化線程池 executorService = Executors.newFixedThreadPool(Runtime.getRuntime() .availableProcessors() * 50); } // 啟動服務 public void start() throws Exception { ss = new ServerSocket(port); while (!quit) { Socket socket = ss.accept();// 接受客戶端的請求 // 為支持多用戶並發訪問，采用線程池管理每一個用戶的連接請求 executorService.execute(new SocketTask(socket));// 啟動一個線程來處理請求 } } // 退出 public void quit() { this.quit = true; try { ss.close(); } catch (IOException e) { e.printStackTrace(); } } public static void main(String[] args) throws Exception { SocketServer server = new SocketServer(7878); server.start(); } private class SocketTask implements Runnable { private Socket socket; public SocketTask(Socket socket) { this.socket = socket; } @Override public void run() { try { System.out.println("accepted connenction from " + socket.getInetAddress() + " @ " + socket.getPort()); PushbackInputStream inStream = new PushbackInputStream( socket.getInputStream()); // 得到客戶端發來的第一行協議數據：Content-Length=143253434;filename=xxx.3gp;sourceid= // 如果用戶初次上傳文件，sourceid的值為空。 String head = StreamTool.readLine(inStream); System.out.println(head); if (head != null) { // 下面從協議數據中讀取各種參數值 String[] items = head.split(";"); String filelength = items[0].substring(items[0].indexOf("=") + 1); String filename = items[1].substring(items[1].indexOf("=") + 1); String sourceid = items[2].substring(items[2].indexOf("=") + 1); Long id = System.currentTimeMillis(); FileLog log = null; if (null != sourceid && !"".equals(sourceid)) { id = Long.valueOf(sourceid); log = find(id);//查找上傳的文件是否存在上傳記錄 } File file = null; int position = 0; if(log==null){//如果上傳的文件不存在上傳記錄,為文件添加跟蹤記錄 String path = new SimpleDateFormat("yyyy/MM/dd/HH/mm").format(new Date()); File dir = new File(uploadPath+ path); if(!dir.exists()) dir.mkdirs(); file = new File(dir, filename); if(file.exists()){//如果上傳的文件發生重名，然后進行改名 filename = filename.substring(0, filename.indexOf(".")-1)+ dir.listFiles().length+ filename.substring(filename.indexOf(".")); file = new File(dir, filename); } save(id, file); }else{// 如果上傳的文件存在上傳記錄,讀取上次的斷點位置 file = new File(log.getPath());//從上傳記錄中得到文件的路徑 if(file.exists()){ File logFile = new File(file.getParentFile(), file.getName()+".log"); if(logFile.exists()){ Properties properties = new Properties(); properties.load(new FileInputStream(logFile)); position = Integer.valueOf(properties.getProperty("length"));//讀取斷點位置 } } } OutputStream outStream = socket.getOutputStream(); String response = "sourceid="+ id+ ";position="+ position+ "\r\n"; //服務器收到客戶端的請求信息后，給客戶端返回響應信息：sourceid=1274773833264;position=0 //sourceid由服務生成，唯一標識上傳的文件，position指示客戶端從文件的什么位置開始上傳 outStream.write(response.getBytes()); RandomAccessFile fileOutStream = new RandomAccessFile(file, "rwd"); if(position==0) fileOutStream.setLength(Integer.valueOf(filelength));//設置文件長度 fileOutStream.seek(position);//移動文件指定的位置開始寫入數據 byte[] buffer = new byte[1024]; int len = -1; int length = position; while( (len=inStream.read(buffer)) != -1){//從輸入流中讀取數據寫入到文件中 fileOutStream.write(buffer, 0, len); length += len; Properties properties = new Properties(); properties.put("length", String.valueOf(length)); FileOutputStream logFile = new FileOutputStream(new File(file.getParentFile(), file.getName()+".log")); properties.store(logFile, null);//實時記錄文件的最后保存位置 logFile.close(); } if(length==fileOutStream.length()) delete(id); fileOutStream.close(); inStream.close(); outStream.close(); file = null; } } catch (Exception e) { e.printStackTrace(); } finally { try { if(socket != null && !socket.isClosed()) socket.close(); } catch (IOException e) {} } } } public FileLog find(Long sourceid) { return datas.get(sourceid); } // 保存上傳記錄 public void save(Long id, File saveFile) { // 日后可以改成通過數據庫存放 datas.put(id, new FileLog(id, saveFile.getAbsolutePath())); } // 當文件上傳完畢，刪除記錄 public void delete(long sourceid) { if (datas.containsKey(sourceid)) datas.remove(sourceid); } private class FileLog { private Long id; private String path; public FileLog(Long id, String path) { super(); this.id = id; this.path = path; } public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getPath() { return path; } public void setPath(String path) { this.path = path; } } } ServerWindow.javapackage com.android.socket.server; import java.awt.BorderLayout; import java.awt.Frame; import java.awt.Label; import java.awt.event.WindowEvent; import java.awt.event.WindowListener; public class ServerWindow extends Frame{ private SocketServer server; private Label label; public ServerWindow(String title){ super(title); server = new SocketServer(7878); label = new Label(); add(label, BorderLayout.PAGE_START); label.setText("服務器已經啟動"); this.addWindowListener(new WindowListener() { @Override public void windowOpened(WindowEvent e) { new Thread(new Runnable() { @Override public void run() { try { server.start(); } catch (Exception e) { e.printStackTrace(); } } }).start(); } @Override public void windowIconified(WindowEvent e) { } @Override public void windowDeiconified(WindowEvent e) { } @Override public void windowDeactivated(WindowEvent e) { } @Override public void windowClosing(WindowEvent e) { server.quit(); System.exit(0); } @Override public void windowClosed(WindowEvent e) { } @Override public void windowActivated(WindowEvent e) { } }); } /** * @param args */ public static void main(String[] args) { ServerWindow window = new ServerWindow("文件上傳服務端"); window.setSize(300, 300); window.setVisible(true); } } StreamTool.javapackage com.android.socket.utils; import java.io.ByteArrayOutputStream; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.PushbackInputStream; public class StreamTool { public static void save(File file, byte[] data) throws Exception { FileOutputStream outStream = new FileOutputStream(file); outStream.write(data); outStream.close(); } public static String readLine(PushbackInputStream in) throws IOException { char buf[] = new char[128]; int room = buf.length; int offset = 0; int c; loop: while (true) { switch (c = in.read()) { case -1: case '\n': break loop; case '\r': int c2 = in.read(); if ((c2 != '\n') && (c2 != -1)) in.unread(c2); break loop; default: if (--room < 0) { char[] lineBuffer = buf; buf = new char[offset + 128]; room = buf.length - offset - 1; System.arraycopy(lineBuffer, 0, buf, 0, offset); } buf[offset++] = (char) c; break; } } if ((c == -1) && (offset == 0)) return null; return String.copyValueOf(buf, 0, offset); } /** * 讀取流 * @param inStream * @return 字節數組 * @throws Exception */ public static byte[] readStream(InputStream inStream) throws Exception{ ByteArrayOutputStream outSteam = new ByteArrayOutputStream(); byte[] buffer = new byte[1024]; int len = -1; while( (len=inStream.read(buffer)) != -1){ outSteam.write(buffer, 0, len); } outSteam.close(); inStream.close(); return outSteam.toByteArray(); } }
運行效果如下:
Android前端控制:
后台監控日志:
下載后的文件路徑:
