Maximum size of data that can be obtained from client socket using socketChannel package nio in java

Question

Using SocketChannel sc =(SocketChannel)key.channel();, we can extract data from the port to the buffer.
To continuously receive data from a port without data loss, what should the code look like?

Here is my code

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

public class MultiPortEcho
{
  private int ports[];
  private ByteBuffer echoBuffer = ByteBuffer.allocate(32000);

  public MultiPortEcho( int ports[] ) throws IOException
  {
    this.ports = ports;
    go();
  }

  private void go() throws IOException
  {
    // Create a new selector
    Selector selector = Selector.open();

    // Open a listener on each port, and register each one
    // with the selector
    for (int i=0; i<ports.length; ++i)
    {
      ServerSocketChannel ssc = ServerSocketChannel.open();
      ssc.configureBlocking( false );
      ServerSocket ss = ssc.socket();
      InetSocketAddress address = new InetSocketAddress( ports[i] );
      ss.bind( address );

      SelectionKey key = ssc.register( selector, SelectionKey.OP_ACCEPT );

      System.out.println( "Going to listen on "+ports[i] );
    }

    while (true)
    {
      int num = selector.select();
      System.out.println("num::::"+num);
      Set selectedKeys = selector.selectedKeys();
      Iterator it = selectedKeys.iterator();

      while (it.hasNext())
      {
        SelectionKey key = (SelectionKey)it.next();

        if ((key.readyOps() & SelectionKey.OP_ACCEPT)== SelectionKey.OP_ACCEPT)
          {
              // Accept the new connection
              ServerSocketChannel ssc = (ServerSocketChannel)key.channel();
              SocketChannel sc = ssc.accept();
              sc.configureBlocking( false );

              // Add the new connection to the selector
              SelectionKey newKey = sc.register(selector,SelectionKey.OP_READ);
              it.remove();

              System.out.println( "Got connection from "+sc );
        }
          else if ((key.readyOps() & SelectionKey.OP_READ)== SelectionKey.OP_READ)
          {
              // Read the data
              SocketChannel sc =(SocketChannel)key.channel();
              System.out.println("sc::::"+sc);
              // data to fetched from channel and dump into the datatbase
              int bytesEchoed = 0;
              //while(true)
              {
                    echoBuffer.clear();
                    int r = sc.read(echoBuffer);
                    System.out.println("r:::" + r);
                    /*int pos=echoBuffer.position();
                    System.out.println("pos:::" +pos);*/
                    if (r == -1)
                    {
                        //echoBuffer.flip();
                        echoBuffer.rewind();
                        byte[] array = new byte[100000];
                        while (echoBuffer.hasRemaining())
                        {
                            int n = echoBuffer.remaining();
                            System.out.println("size:" + n);
                            echoBuffer.get(array,0,n );
                            System.out.println(new String(array,0,n));
                            key.cancel();
                            it.remove();

                        }

                    }

                    /*int pos=echoBuffer.position();
                    System.out.println("pos:::" + pos);
                    if(r<=0)
                    {
                        echoBuffer.flip();
                        for (int j = 0; j < pos; j++ )
                        {
                            String ss =Integer.toHexString(echoBuffer.get());
                            if (ss.length() == 1)
                                System.out.print("0" + ss + " ");
                            else if (ss.length() > 2)
                                System.out.print(ss.substring(6) + " ");
                            else System.out.print(ss + " ");
                        }
                      break;
                    }

                    echoBuffer.flip();

                    sc.write( echoBuffer );
                    bytesEchoed += r;*/
              }

             //System.out.println( "Echoed "+bytesEchoed+" from "+sc );
             //it.remove();
        }

      }

//System.out.println( "going to clear" );
//      selectedKeys.clear();
//System.out.println( "cleared" );
    }
  }

  static public void main( String args[] ) throws Exception
  {
    FileOutputStream fileoutputstream = new FileOutputStream("MultiPort.txt", false);
    PrintStream printstream = new PrintStream(fileoutputstream);
    System.setOut(printstream);
    if (args.length<=0) {
      System.err.println( "Usage: java MultiPortEcho port [port port ...]" );
      System.exit( 1 );
    }

    int ports[] = new int[args.length];

    for (int i=0; i<args.length; ++i) {
      ports[i] = Integer.parseInt( args[i] );
    }

    new MultiPortEcho( ports );
  }
}

Answer 1

The maximum size you can read is actually limited by the amount of your memory.

However, you do not need to read super large blocks for efficiency. You should find that 1 MB is more than enough. In fact, you may find that the 4 KB blocks are large enough to get the maximum bandwidth for a 1 GB connection.

Answer 2

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Answer 3

SocketChannelHandler, readFromChannel() .

        public void readFromChannel() {
        try {
                   [...]
                   if (readBuffer != null) {
                readBuffer.flip();
                receivingBroker.broker(readBuffer, false);
                if (readBuffer != null) {
                    readBuffer.clear();
                    readBuffer = null;
                }
            }
            if (readBuffer == null || !readBuffer.hasRemaining()) {
                getThread().removeInterestOp(this, SelectionKey.OP_READ);
                getThread().addInterestOp(this, SelectionKey.OP_WRITE);
            }
            if (receivingBroker.isClosed()) {
                if (getChannelListener() != null) {
                    getChannelListener().readFinished(this);
                }
            }
         } catch (Exception e) {
              e.printStackTrace();
         }
         }

Answer 4

key.cancel(). , , .

Answer 5

NIO, /.

socketChannel.socket().setReceiveBufferSize(512);
socketChannel.socket().setSendBufferSize(16);

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