java socket长连接传输文件

一个简单的demo，实现Java socket文件传输。线程就不写了，只为了实现文件传输。
前面四个字节表示文件大小（长度），后面为数据体，数据体往后五个字节表示文件后缀名，后缀名超过五个字节的，则为二进制文件，丢弃文件后缀。

服务端接收
下面是服务端代码：

package receptionData;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class Test {

    public static void main(String[] args) {
        try {
            ServerSocket s = new ServerSocket(8896);
            Socket sc = s.accept();
            InputStream in = sc.getInputStream();
            int t = 1;
            while(true){
                byte[] lData = new byte[4];
                in.read(lData);
                int length = byteArrayToInt(lData);
                System.out.println("文件大小："+length+"字节");
                byte[] dt2 = new byte[length];

                readData(in,dt2);

                byte[] type = new byte[5];

                in.read(type);

                String typeStr = new String(type);
                System.out.println("文件类型："+typeStr.trim());
                File of = new File("D:/RRR"+t+"."+typeStr.trim());
                of.createNewFile();
                OutputStream o = new FileOutputStream(of);

                o.write(dt2);
                o.flush();
                o.close();
                t++;




            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

    private static int byteArrayToInt(byte[] b) {
        return b[3] & 0xFF |
                (b[2] & 0xFF) << 8 |
                (b[1] & 0xFF) << 16 |
                (b[0] & 0xFF) << 24;
    }

    private static byte[] intToByteArray(int a) {
        return new byte[]{
                (byte) ((a >> 24) & 0xFF),
                (byte) ((a >> 16) & 0xFF),
                (byte) ((a >> 8) & 0xFF),
                (byte) (a & 0xFF)
        };
    }

    /**
     * 
     * @param in
     * @param bData
     * @throws IOException
     */
    private static void readData(InputStream in,byte[] bData) throws IOException{
        int off = 0;
        int length = bData.length;
        int readLength = 0;
        do{
            off = readLength+off;
            length = length-readLength;
            readLength = in.read(bData, off, length);
        }while(readLength!=length);
    }


}

客户端发送
下面是客户端代码：

package sendData;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.Scanner;

public class Test {

    public static void main(String[] args) {
        try {
            Scanner sn = new Scanner(System.in);
            Socket s = new Socket("127.0.0.1",8896);
            OutputStream out = s.getOutputStream();
            while(true){
                System.out.println("请输入文件路径");
                String pathAndFileName = sn.nextLine();
                File f = new File(pathAndFileName);
                if(!f.exists()){
                    System.out.println("文件不存在");
                    continue;
                }else{
                    InputStream in = new FileInputStream(f);
                    int length = (int) f.length();
                    if(length>1024*1024*5){
                        System.out.println("文件过大");
                        continue;
                    }else{

                        String[] tempFileType = pathAndFileName.split("\\.");
                        String fileType = tempFileType[tempFileType.length-1];
                        byte[] typeData = fileType.getBytes();
                        byte[] sendTypeData = new byte[5];
                        if(typeData.length<5){
                            System.arraycopy(typeData, 0, sendTypeData, 0, typeData.length);
                        }

                        byte[] tempData = new byte[length];
                        in.read(tempData);
                        in.close();

                        byte[] lengthData = intToByteArray(length);
                        byte[] sendData = new byte[tempData.length+lengthData.length+sendTypeData.length];

                        System.arraycopy(lengthData, 0, sendData, 0, lengthData.length);
                        System.arraycopy(tempData, 0, sendData, lengthData.length, tempData.length);
                        System.arraycopy(sendTypeData, 0, sendData, lengthData.length+tempData.length, sendTypeData.length);

                        out.write(sendData);
                        out.flush();
                    }
                }
            }
        } catch (UnknownHostException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    private static int byteArrayToInt(byte[] b) {
        return b[3] & 0xFF |
                (b[2] & 0xFF) << 8 |
                (b[1] & 0xFF) << 16 |
                (b[0] & 0xFF) << 24;
    }

    private static byte[] intToByteArray(int a) {
        return new byte[]{
                (byte) ((a >> 24) & 0xFF),
                (byte) ((a >> 16) & 0xFF),
                (byte) ((a >> 8) & 0xFF),
                (byte) (a & 0xFF)
        };
    }

}

每次最多只能发小于5M的文件，超过需要自己分批发送和接收数据。如果会上面的代码实现10G的传输应该也不难。

传输效果：

传输了两个jpg，两个txt文件

接收到的文件：