UDP套接字发送和接收

Question

我想实现一个UDP客户端服务器。客户端使用rdt_send函数发送1032个字节，但服务器仅在客户端执行两次后才接收此数据包。

下面是代码：

rdt_send：

public void rdt_send(byte[] buffer, Integer mss, DatagramSocket s,Integer seqNum) throws IOException 
{ 
    int i,j,k; 
    byte[] seq_num = new byte[4]; 
    byte[] seqnum_temp = new byte[4]; 
    byte [] checksum = new byte[2]; 
    byte [] udp_field = new BigInteger("0101010101010101",2).toByteArray(); 
    Integer checksum_value = (int)calculateChecksum(buffer); 
    checksum = new BigInteger(checksum_value.toString(), 10).toByteArray(); 
    seqnum_temp = new BigInteger(seqNum.toString(),10).toByteArray(); 
    System.out.println(checksum_value); 
    Integer length_temp = seqnum_temp.length; 
    if (seqnum_temp.length<4) 
    { 
     Integer append = 4 -seqnum_temp.length; 
     for (i=0;i<append;i++) 
     { 
      seq_num[i] = 0; 
     } 
     for (j = append, k=0 ; j<4 && k<length_temp ; j++,k++) 
     { 
      seq_num[j] = seqnum_temp[k]; 
     } 

     System.out.println(seq_num[0]); 
    } 

    byte[] finalSend = new byte[mss+8]; 

    for (i=0;i<4;i++) 
    { 
     finalSend[i] = seq_num[i]; 

    } 
    for (i=4,k=0;i<6 && k<2;i++,k++) 
    { 
     finalSend[i] = checksum[k]; 
    } 
    for (i=6,k=0;i<8 && k<2 ;i++,k++) 
    { 
     finalSend[i] = udp_field[k]; 
    } 
    for (i=8,k=0;i<finalSend.length && k< buffer.length;i++,k++) 
    { 
     finalSend[i] = buffer[k]; 
    } 

    for (i=0;i<finalSend.length;i++) 
    { 
     System.out.println(finalSend[i]); 
    } 
    System.out.println("Got to final sending stage"); 
    DatagramPacket p = new DatagramPacket (finalSend,finalSend.length,InetAddress.getLocalHost(),7771); 
    s.send(p); 
    System.out.println("Sent datagram"); 

} 

客户端：

package simpleFTP; 


public class SimpleFTPClient { 



public static void main(String args[]) throws IOException{ 

    Integer seq_num =512; 
    Utils u = new Utils(); 
    DatagramSocket d = new DatagramSocket(); 
    File f =new File("C:/Users/amoolp/Desktop/client3/3333.txt"); 
    FileInputStream fs = new FileInputStream(f); 
    byte[] bytesRead = new byte[1024]; 
    fs.read(bytesRead,0,1024); 

    //DatagramPacket p = new DatagramPacket (bytesRead,bytesRead.length,InetAddress.getLocalHost(),7771); 
    // d.send(p); 
    u.rdt_send(bytesRead,1024,d,seq_num); 




} 



} 

服务器：

public class Server { 

public static void main (String args[]) throws IOException 
{ 
    DatagramSocket dg = new DatagramSocket (7771); 

    byte[] buf = new byte[1032]; 
    DatagramPacket packet = new DatagramPacket(buf, buf.length); 
    System.out.println("Waiting to receive packet"); 
    dg.receive(packet); 
    System.out.println("Received packet"); 
    for (int i=0; i<buf.length ; i++) 
    { 
    System.out.println(buf[i]); 
    } 
    } 

} 

任何想法，为什么发生这种情况？

Answer 1

这是由于缓冲区。在发送数据包后刷新（）套接字。