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雜談socket編程

作者：xcbeyond
瘋狂源自夢(mèng)想，技術(shù)成就輝煌！微信公眾號(hào)：《程序猿技術(shù)大咖》號(hào)主，專注后端開發(fā)多年，擁有豐富的研發(fā)經(jīng)驗(yàn)，樂于技術(shù)輸出、分享，現(xiàn)階段從事微服務(wù)架構(gòu)項(xiàng)目的研發(fā)工作，涉及架構(gòu)設(shè)計(jì)、技術(shù)選型、業(yè)務(wù)研發(fā)等工作。對(duì)于Java、微服務(wù)、數(shù)據(jù)庫、Docker有深入了解，并有大量的調(diào)優(yōu)經(jīng)驗(yàn)。

最近在寫一些與網(wǎng)絡(luò)編程相關(guān)的小工具，不得不再把網(wǎng)絡(luò)編程的知識(shí)再回顧回顧了。一提起網(wǎng)絡(luò)編程，勢(shì)必局想到了一位核心人物Socket，是她撐起了網(wǎng)絡(luò)編程的半邊天，使得網(wǎng)絡(luò)編程得以繼續(xù)。

什么是Socket？

通常也稱作"套接字"，應(yīng)用程序通過Socket向網(wǎng)絡(luò)發(fā)出請(qǐng)求或者應(yīng)答網(wǎng)絡(luò)請(qǐng)求。它是在應(yīng)用層與TCP/IP協(xié)議族通信的中間軟件抽象層，它是一組接口，用來組織傳輸?shù)臄?shù)據(jù)。下面就用一張圖來說明下“三次握手”：

網(wǎng)絡(luò)間的通信，是建立在授受雙方的，即：服務(wù)器與客戶端。服務(wù)器端時(shí)刻處于啟動(dòng)狀態(tài)，不停地監(jiān)聽著客戶端發(fā)來的請(qǐng)求信息，并給予應(yīng)答，當(dāng)客戶端向服務(wù)器發(fā)來一條數(shù)據(jù)請(qǐng)求時(shí)，服務(wù)器接受到了這條請(qǐng)求后，驗(yàn)證成功后，給出回復(fù)，建立鏈接通信，即一次握手。類似數(shù)據(jù)傳輸交換、斷開鏈接又是兩次握手。下面就以一段代碼來做一分析說明吧。（Java版）

服務(wù)端：

<span style="font-size:14px;">import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileFilter;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
/**
* FTP服務(wù)器端
* @author xcbeyond
* 2014-6-7 22:12:21
*/

public class FtpServer {
   public static void main(String[] args) throws Exception{
       FtpServer server = new FtpServer();
       server.listen(8800);

   }
//用來時(shí)刻監(jiān)聽來自客戶端請(qǐng)求的監(jiān)聽者
   public void listen(int port) throws Exception{
       ServerSocket ss = new ServerSocket(port);
       while(true) {
           System.out.println("等待客戶端連接...");
           Socket socket = ss.accept();
           System.out.println("客戶連接進(jìn)來了。");
           new ClientAgent(socket).start();
       }
   }

   class ClientAgent extends Thread{
       Socket socket;
       InputStream in;
       OutputStream out;
       public ClientAgent(Socket socket) throws Exception{
           this.socket = socket;
           in = socket.getInputStream();
           out = socket.getOutputStream();
       }
       @Override
       public void run() {
           BufferedReader in = new BufferedReader(
                               new InputStreamReader(this.in));
           PrintWriter out = new PrintWriter(this.out,true);//true自動(dòng)清除緩存相當(dāng)于fulsh()
           try{
               out.println("text,1");
               out.println("你好歡迎使用FTP Demo!");
               while(true) {
                   String cmd = in.readLine();
                   if("?".equals(cmd)) {
                       out.println("text,1");
                       out.println("支持命令：ls,get,?,bye");
                   }
                   else if("ls".equals(cmd)) {
                       listDir(out);
                   }
                   else if(cmd.matches("^get\\s+.+")) {
                       sendFile(cmd,out,this.out);
                   }
                   else{
                       out.println("text,1");
                       out.println("不知可否！");
                   }
               }
           }catch(Exception e) {
               e.printStackTrace();
           }
       }
       private void sendFile(String cmd, PrintWriter out,OutputStream os) throws IOException{
           String name = cmd.split("\\s+")[1];
           File file = new File(name);
           if(!file.exists()){
               out.println("text,1");
               out.println("沒有找到文件！ "+name);
               return;
           }
           out.println("file,"+file.length()+","+name);
           InputStream in = new BufferedInputStream(
                                   new FileInputStream(file));
           int b;
           while((b = in.read())!=-1){
               os.write(b);
           }
           os.flush();
           in.close();
       }
       /**
       * 列出文件目錄
       * @param out
       */
       private void listDir(PrintWriter out) {
           File dir = new File(".");
           File[] files = dir.listFiles(new FileFilter() {
               public boolean accept(File pathname) {
                   return pathname.isFile();
               }
           });
           out.println("text,"+files.length+1);
           out.println("在目錄："+dir+"中，有文件："+files.length);
           for (File file : files) {
               out.println(file.getName());
           }
       }
   }
}
</span>

客戶端：

import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.Socket;
/**
*
* @author xcbeyond
* 2014-6-7 23:16:53
*/
public class FtpClient {
   Socket socket;
   OutputStream out;
   InputStream in;
   public static void main(String[] args) throws Exception{
       FtpClient client = new FtpClient();
       client.open("localhost",8800);
   }
   public void open(String host,int port) throws Exception{
       socket = new Socket(host,port); //對(duì)指定IP，端口的服務(wù)程序發(fā)出請(qǐng)求，建立通信
       in = socket.getInputStream();
       out =socket.getOutputStream();
       new RequestSender(out).start();
       new ResponseReceiver(in).start();
   }

   class RequestSender extends Thread{
       OutputStream out;
       public RequestSender(OutputStream out) {
           this.out = out;
       }
       @Override
       public void run() {
           PrintWriter out = new PrintWriter(this.out,true);
           BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
           String str;
           try{
               while((str = in.readLine())!=null) {
                   out.println(str);
               }
           }catch(Exception e){
               e.printStackTrace();
           }
       }
   }
   class ResponseReceiver extends Thread {
       InputStream in;
       public ResponseReceiver(InputStream in) {
           this.in = in;
       }
       public void run() {
           BufferedReader in = new BufferedReader(new InputStreamReader(this.in));
           try{
               String str;
               while((str = in.readLine())!=null) {
                   if(str.startsWith("text")) {
                       String num = str.substring(str.indexOf(",")+1);
                       printText(in,Integer.parseInt(num));
                   }
                   else if(str.startsWith("file")){//file,4567，filename
                       saveFile(this.in,str);
                   }
               }
           }catch(Exception e) {
               e.printStackTrace();
           }
       }
       /**
       * 保存文件
        * @param in
       * @param size
       */
       private void saveFile(InputStream in, String head) throws IOException{
           String[] data = head.split(",");
           int length = Integer.parseInt(data[1]);
           String name = data[2];
           OutputStream out = new BufferedOutputStream(new FileOutputStream("ftp-"+name));
            for (int i = 0; i < length; i++) {
               int b = in.read();
               out.write(b);
           }
           out.close();
           System.out.println("下載了文件："+name);
       }
        /**
       * 打印出文本內(nèi)容
       * @param in
       * @param num
       * @throws Exception
       */
       private void printText(BufferedReader in, int num) throws Exception{
           for (int i = 0; i < num; i++) {
               System.out.println(in.readLine());
           }
       }

   }
}

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