如何在Java中使用UDP發送文件

Question

我有一個使用java的套接字編程項目。我們必須編寫客戶端和服務器代碼來傳輸一個文件，代碼在編譯時沒有顯示錯誤，但是沒有執行，當我放置文件名時它會凍結。

我知道，UDP不是用於發送文件是個好主意，但我必須這樣做的一個項目，我的代碼是：

客戶端代碼

import java.io.*; 
import java.net.*; 
import java.util.*; 
public class Client 
{ 
static InetAddress dest; 
public static void main(String [] args) throws Exception 
{ 

    DatagramSocket clskt = new DatagramSocket(); 
    Scanner input = new Scanner (System.in); 
    int port =input.nextInt(); 
    System.out.println("Enter Destination Host name"); 
    String hostname=input.next(); 
    dest.getByName(hostname); 
    int packetcount=0; 
    System.out.println("Enter The path of the file you want to send"); 
    String path = input.next(); 
    File initialFile = new File(path); 
      FileInputStream targetStream = new FileInputStream(initialFile); 
    int filesize=targetStream.available(); 
    //int neededpackets =(int)Math.ceil((double)(size/1024)); 
    byte [] data= new byte[1024]; 
    // counting bytes 
    for (int i=0;i<1024;i++) 
    { 
     data[i]=(byte)targetStream.read(); 
    } 
    //create a packet 
    DatagramPacket clpkt=new DatagramPacket(data,data.length,dest,port); 
    packetcount++; 
    clskt.send(clpkt); 
    if(packetcount >neededpackets) 
     clskt.close(); 
    } 

} 

服務器代碼

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

class Server1 
    { 
public static void main(String args[])throws Exception 
{ 
    System.out.println("Enter Port number !!!"); 
    Scanner input = new Scanner(System.in); 
    int SPort = input.nextInt(); 
    DatagramSocket srvskt = new DatagramSocket(SPort); 
    byte[] data =new byte[1024]; 
    System.out.println("Enter a full file name to save data to it ?"); 
    String path = input.next(); 
    System.out.println("file : "+path+" will be created."); 
    FileOutputStream FOS = new FileOutputStream(path); 
    DatagramPacket srvpkt = new DatagramPacket(data,1024); 
    System.out.println("listening to Port: "+SPort); 
    int Packetcounter=0;//packet counter 
    while(true) 
     { 
      srvskt.receive(srvpkt); 
      Packetcounter++; 
      String words = new String(srvpkt.getData()); 
      InetAddress ip= srvpkt.getAddress(); 
      int port = srvpkt.getPort(); 
      System.out.println("Packet # :"+Packetcounter+" 
      Received from Host/Port: "+ip+"/"+port); 
      FOS.write(data); 
      //out16.flush(); 
      if (Packetcounter >=100) 
       break; 

     } 
    FOS.close();//releasing file. 
    System.out.println("Data has been written to the file !"); 
    } 
} 

預先感謝所有人。

Answer 1

這是我掀起的一個簡單例子。它使用DatagramSocket連接，我認爲這是唯一的方法。

public class BroadcastTest 
{ 
    private static final int RANDOM_PORT = 4444; 

    public static void main(String[] args) 
      throws Exception 
    { 
     InetAddress addr = InetAddress.getByName("127.0.0.1"); 
     DatagramSocket dsock = new DatagramSocket(); 
     byte[] send = "Hello World".getBytes("UTF-8"); 
     DatagramPacket data = new DatagramPacket(send, send.length, addr, RANDOM_PORT); 
     dsock.send(data); 
    } 
} 

這裏的服務器代碼。這些似乎工作，但我沒有徹底測試它們！

class Server { 
    private static final int RANDOM_PORT = 4444; 

    public static void main(String[] args) { 
     try { 
     DatagramSocket dsock = new DatagramSocket(RANDOM_PORT); 
     DatagramPacket data = new DatagramPacket(new byte[ 64*1024 ], 64*1024); 
     dsock.receive(data); 
     System.out.println(new String(data.getData(), 0, 
       data.getLength(), "UTF-8")); 
     } catch(SocketException ex) { 
     Logger.getLogger(Server.class.getName()). 
       log(Level.SEVERE, null, ex); 
     } catch(IOException ex) { 
     Logger.getLogger(Server.class.getName()). 
       log(Level.SEVERE, null, ex); 
     } 
    } 
} 

Answer 2

我看到在客戶第一眼就是dest字段您嘗試使用從未得到未初始化，但它仍然無效。你應該寫dest = InetAddress.getByName(anArgument)，以便dest得到一個新的InetAddress實例的值。所以，當代碼變得可編譯時，很可能你會得到Null指針異常。現在它不是，只要neededpackets沒有定義。