java Socket文件传输

通常在java Socket编程中，通常会遇到文件传输的情况。文件传输有两种方式字节流和字符流，那么哪些文件用字符流哪些文件用字节流呢？一般的文本文件用字符流，在用字符流的过程中注意在发送方和接收方统一文件的编码；其他类型文件一般采用字节流，可防止文件在传输过程中发生变化。
有时候我们会发现文件经过传输之后发生变化（例如图片损坏，应用程序无法运行等）。查看文件属性，发现文件大小没有变化，但是采用MD5文件校验时发现传输前后md5发生了变化，这通常就是由于采用不正确的传输流造成的。
下面的例子以字节流为例，展示了java Socket文件传输。

//客户端 import java.io.BufferedInputStream; import java.io.DataInputStream; import java.io.DataOutputStream; import java.io.FileInputStream; import java.io.IOException; import java.io.PrintWriter; import java.net.Socket; import java.net.UnknownHostException;    public class Client {     privateSocket socket = null;     PrintWriter socketWriter =null;        publicvoid connect() throws UnknownHostException, IOException {         socket =new Socket("192.168.1.104",8080);     }        publicvoid transferFile() throws IOException {         FileInputStream is =new FileInputStream("D:\test.exe");            DataInputStream fiins =new DataInputStream(newBufferedInputStream(is));         DataOutputStream fileous =new DataOutputStream(socket                 .getOutputStream());            intn = 512, m;         bytebuffer[] = new byte[n];         while((m = fiins.read(buffer, 0, n)) != -1&& m > 0) {             fileous.write(buffer,0, m); //这里要注意  读取多少字节 写入多少字节             fileous.flush();         }         fileous.flush();         fileous.close();         fiins.close();         socket.getOutputStream().close();         socketWriter.close();     } }    //服务器端代码 import java.io.DataInputStream; import java.io.DataOutputStream; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.net.ServerSocket; import java.net.Socket;    public class Server {     privateServerSocket server = null;     privateSocket socket = null;            publicvoid connect() throws IOException{         server =new ServerSocket(8080,5);         socket = server.accept();         System.out.println(socket.getInetAddress());     }            publicvoid getFile() throws IOException{         InputStream in = socket.getInputStream();         File file =new File("E:\\text.exe");                               DataInputStream fileStream =new DataInputStream(in);         FileOutputStream os =new FileOutputStream(file);         DataOutputStream out =new DataOutputStream(os);                    intn = 512,m;         bytebuffer[] = new byte[n];         while(((m=fileStream.read(buffer,0, n))!=-1) && (m>0)){             out.write(buffer,0,m);         }         out.close();         in.close();         os.close();         System.out.println("ok");         socket.close();         server.close();     } }