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POUDP Sockets send and receive
 

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  1. POUDP Sockets send and receive
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    <p>I am trying to implement a UDP client server. The client is sending 1032 bytes using the rdt_send function but the server receives this packet only after the client is executed twice. </p> <p>Here is the code for :</p> <p>rdt_send:</p> <pre><code>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&lt;4) { Integer append = 4 -seqnum_temp.length; for (i=0;i&lt;append;i++) { seq_num[i] = 0; } for (j = append, k=0 ; j&lt;4 &amp;&amp; k&lt;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&lt;4;i++) { finalSend[i] = seq_num[i]; } for (i=4,k=0;i&lt;6 &amp;&amp; k&lt;2;i++,k++) { finalSend[i] = checksum[k]; } for (i=6,k=0;i&lt;8 &amp;&amp; k&lt;2 ;i++,k++) { finalSend[i] = udp_field[k]; } for (i=8,k=0;i&lt;finalSend.length &amp;&amp; k&lt; buffer.length;i++,k++) { finalSend[i] = buffer[k]; } for (i=0;i&lt;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"); } </code></pre> <p>client :</p> <pre><code>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); } } </code></pre> <p>Server :</p> <pre><code>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&lt;buf.length ; i++) { System.out.println(buf[i]); } } } </code></pre> <p>Any ideas as to why this is happening?</p>
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    1. PTQuestion
    1. USBenjamin
    1. USuser1563603
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    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
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      1. PTAnswer
    1. This table or related slice is empty.
    1. COWorks for me, every time, but you should certainly close the `DatagramSocket` in the client before it exits.
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      1. POUDP Sockets send and receive
      1. USuser207421
 

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