Java基于Socket文件传输示例

原文: http://www.blogjava.net/sterning/archive/2007/10/13/152508.html
数据丢失: http://topic.csdn.net/u/20100523/21/5a1a055f-af64-4e01-b669-7ff46f20b4ed.html

解决数据丢失的一个办法:当发送端发完数据之后，就应该让接收端告诉发送端“接收完成”，然后接收端先关闭，发送端才关闭，顺序很重要。

最近需要进行网络传输大文件，于是对基于socket的文件传输作了一个初步的了解。在一位网友提供的程序基础上，俺进行了一些加工，采用了缓冲输入/输出流来包装输出流，再采用数据输入/输出输出流进行包装，加快传输的速度。废话少说，先来看服务器端的程序。

1.服务器端

package sterning;

import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class ServerTest {
    int port = 8821;

    void start() {
        Socket s = null;
        try {
            ServerSocket ss = new ServerSocket(port);
            while (true) {
                // 选择进行传输的文件
                String filePath = "D:\\lib.rar";
                File fi = new File(filePath);

                System.out.println("文件长度:" + (int) fi.length());

                // public Socket accept() throws
                // IOException侦听并接受到此套接字的连接。此方法在进行连接之前一直阻塞。

                s = ss.accept();
                System.out.println("建立socket链接");
                DataInputStream dis = new DataInputStream(new BufferedInputStream(s.getInputStream()));
                dis.readByte();

                DataInputStream fis = new DataInputStream(new BufferedInputStream(new FileInputStream(filePath)));
                DataOutputStream ps = new DataOutputStream(s.getOutputStream());
                //将文件名及长度传给客户端。这里要真正适用所有平台，例如中文名的处理，还需要加工，具体可以参见Think In Java 4th里有现成的代码。
                ps.writeUTF(fi.getName());
                ps.flush();
                ps.writeLong((long) fi.length());
                ps.flush();

                int bufferSize = 8192;
                byte[] buf = new byte[bufferSize];

                while (true) {
                    int read = 0;
                    if (fis != null) {
                        read = fis.read(buf);
                    }

                    if (read == -1) {
                        break;
                    }
                    ps.write(buf, 0, read);
                }
                ps.flush();
                // 注意关闭socket链接哦，不然客户端会等待server的数据过来，
                // 直到socket超时，导致数据不完整。                
                fis.close();
                s.close();                
                System.out.println("文件传输完成");
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String arg[]) {
        new ServerTest().start();
    }
}

2.socket的Util辅助类

package sterning;

import java.net.*;
import java.io.*;

public class ClientSocket {
    private String ip;

    private int port;

    private Socket socket = null;

    DataOutputStream out = null;

    DataInputStream getMessageStream = null;

    public ClientSocket(String ip, int port) {
        this.ip = ip;
        this.port = port;
    }

    /**
     * 创建socket连接
     * 
     * @throws Exception
     *             exception
     */
    public void CreateConnection() throws Exception {
        try {
            socket = new Socket(ip, port);
        } catch (Exception e) {
            e.printStackTrace();
            if (socket != null)
                socket.close();
            throw e;
        } finally {
        }
    }

    public void sendMessage(String sendMessage) throws Exception {
        try {
            out = new DataOutputStream(socket.getOutputStream());
            if (sendMessage.equals("Windows")) {
                out.writeByte(0x1);
                out.flush();
                return;
            }
            if (sendMessage.equals("Unix")) {
                out.writeByte(0x2);
                out.flush();
                return;
            }
            if (sendMessage.equals("Linux")) {
                out.writeByte(0x3);
                out.flush();
            } else {
                out.writeUTF(sendMessage);
                out.flush();
            }
        } catch (Exception e) {
            e.printStackTrace();
            if (out != null)
                out.close();
            throw e;
        } finally {
        }
    }

    public DataInputStream getMessageStream() throws Exception {
        try {
            getMessageStream = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
            return getMessageStream;
        } catch (Exception e) {
            e.printStackTrace();
            if (getMessageStream != null)
                getMessageStream.close();
            throw e;
        } finally {
        }
    }

    public void shutDownConnection() {
        try {
            if (out != null)
                out.close();
            if (getMessageStream != null)
                getMessageStream.close();
            if (socket != null)
                socket.close();
        } catch (Exception e) {

        }
    }
}

3.客户端

package sterning;

import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileOutputStream;

public class ClientTest {
    private ClientSocket cs = null;

    private String ip = "localhost";// 设置成服务器IP

    private int port = 8821;

    private String sendMessage = "Windwos";

    public ClientTest() {
        try {
            if (createConnection()) {
                sendMessage();
                getMessage();
            }

        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    private boolean createConnection() {
        cs = new ClientSocket(ip, port);
        try {
            cs.CreateConnection();
            System.out.print("连接服务器成功!" + "\n");
            return true;
        } catch (Exception e) {
            System.out.print("连接服务器失败!" + "\n");
            return false;
        }

    }

    private void sendMessage() {
        if (cs == null)
            return;
        try {
            cs.sendMessage(sendMessage);
        } catch (Exception e) {
            System.out.print("发送消息失败!" + "\n");
        }
    }

    private void getMessage() {
        if (cs == null)
            return;
        DataInputStream inputStream = null;
        try {
            inputStream = cs.getMessageStream();
        } catch (Exception e) {
            System.out.print("接收消息缓存错误\n");
            return;
        }

        try {
            //本地保存路径，文件名会自动从服务器端继承而来。
            String savePath = "E:\\";
            int bufferSize = 8192;
            byte[] buf = new byte[bufferSize];
            int passedlen = 0;
            long len=0;
            
            savePath += inputStream.readUTF();
            DataOutputStream fileOut = new DataOutputStream(new BufferedOutputStream(new BufferedOutputStream(new FileOutputStream(savePath))));
            len = inputStream.readLong();
            
            System.out.println("文件的长度为:" + len + "\n");
            System.out.println("开始接收文件!" + "\n");
                    
            while (true) {
                int read = 0;
                if (inputStream != null) {
                    read = inputStream.read(buf);
                }
                passedlen += read;
                if (read == -1) {
                    break;
                }
                //下面进度条本为图形界面的prograssBar做的，这里如果是打文件，可能会重复打印出一些相同的百分比
                System.out.println("文件接收了" +  (passedlen * 100/ len) + "%\n");
                fileOut.write(buf, 0, read);
            }
            System.out.println("接收完成，文件存为" + savePath + "\n");

            fileOut.close();
        } catch (Exception e) {
            System.out.println("接收消息错误" + "\n");
            return;
        }
    }

    public static void main(String arg[]) {
        new ClientTest();
    }
}

这就实现了从服务器端向客户端发送文件的过程,当然,反过来,也一样.稍有不同.代码中对跨平台的细节没有实现,有时间或兴趣的朋友可以提供一下.