Java，通过套接字发送大文件消耗太多CPU周期并且速度慢

Question

这个问题已经有答案了:

Java sending and receiving file (byte[]) over sockets (6 个回答)

已关闭 8 年前。

我正在尝试JAVA，并在网上发现了这个问题。

Java sending and receiving file (byte[]) over sockets .

出于好奇，我使用了已接受答案中的代码，以及我发现与问题类似的其他代码。我尝试了接受的答案，是的，它有效并且速度非常快。但问题是存档文件已损坏。这是我尝试过的其他代码。我的实验代码的缺点是它消耗 CPU 周期并且比接受的答案花费更多的时间(而且我不知道为什么会这样)。这是我的代码。有人可以帮助我进一步优化和改进这段代码吗？

接受答案所花费的时间 = 4 Mb 文件 11 毫秒。我的实验花费的时间 = 相同文件 4 秒。

服务器.java

public class Server implements Runnable {

 private ServerSocket serverSocket = null;
 private Socket socket = null;
 private ObjectInputStream inStream = null;

 public Server() {

 }

 @Override
 public void run() {

     try {
    serverSocket = new ServerSocket(4445);
    socket = serverSocket.accept();
    DataInputStream dIn = new DataInputStream(socket.getInputStream());
    OutputStream os = socket.getOutputStream();
    DataOutputStream outToClient = new DataOutputStream(os);

    System.out.println("Connected");
    File myFile = new File("lib1.zip");
    long flength = myFile.length();
    System.out.println("File Length"+flength);
    outToClient.writeLong(flength);
    FileInputStream fis;
    BufferedInputStream bis;
    byte[] mybytearray = new byte[8192];
    fis = new FileInputStream(myFile);
    bis = new BufferedInputStream(fis);
    int theByte = 0;
    System.out.println("Sending " + myFile.getAbsolutePath() + "(" + myFile.length() + " bytes)");
       while ((theByte = bis.read()) != -1) {
     outToClient.write(theByte);
     // bos.flush();
     }
    /*int count;
    BufferedOutputStream bos= new BufferedOutputStream(os);
    while ((count = bis.read(mybytearray))>0) {
        bos.write(mybytearray, 0, count);
    }*/

    bis.close();
    socket.close();

} catch (SocketException se) {

    System.exit(0);
} catch (IOException e) {
    e.printStackTrace();
}
 }

 public static void main(String[] args) {
     Thread t = new Thread(new Server());
     t.start();
 }
 }

接收文件.java

 public class RecieveFile {

 public final static int SOCKET_PORT = 4445;      // you may change this
 String SERVER = "127.0.0.1";  // localhost
 ArrayList<String> logmsg = new ArrayList<>();
 public static void main(String[] args) {
     new RecieveFile();
 }

 public RecieveFile() {
     try (Socket sock = new Socket(SERVER, SOCKET_PORT)) {

    System.out.println("Connecting...");
    try (OutputStream os = sock.getOutputStream(); DataOutputStream outToServer = new DataOutputStream(os)) {
        try (DataInputStream dIn = new DataInputStream(sock.getInputStream())) {
            long fileLen, downData;
            int bufferSize = sock.getReceiveBufferSize();

            long starttime = System.currentTimeMillis();
            File myFIle = new File("lib1.zip");
            try (FileOutputStream fos = new FileOutputStream(myFIle); BufferedOutputStream bos = new BufferedOutputStream(fos)) {
                fileLen = dIn.readLong();
                /*for (long j = 0; j <= fileLen; j++) {
                 int tempint = is.read();
                 bos.write(tempint);
                 }*/
                downData = fileLen;
                int n = 0;
                byte[] buf = new byte[8192];
                    while (fileLen > 0 && ((n = dIn.read(buf, 0, buf.length)) != -1)) {
                 bos.write(buf, 0, n);
                 fileLen -= n;
                 //            System.out.println("Remaining "+fileLen);
                 }
                /*while ((n = dIn.read(buf)) > 0) {
                    bos.write(buf, 0, n);
                }*/
                bos.flush();
                long endtime = System.currentTimeMillis();
                System.out.println("File " + myFIle.getAbsolutePath()
                        + " downloaded (" + downData + " bytes read) in " + (endtime - starttime) + " ms");

            }
        }
    }
} catch (IOException ex) {
    Logger.getLogger(RecieveFile.class.getName()).log(Level.SEVERE, null, ex);
}

 }
 }

Answer 1

您一次复制一个字节。这很慢。您还声明了一个字节数组但没有使用它。试试这个:

int count;
byte[] buffer = new byte[8192]; // or more, double or quadruple it

while ((count = in.read(buffer)) > 0)
{
    out.write(buffer, 0, count);
}