Echoclient + MulServer

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

class MulClient
{
  public static void main( String[] args )
  {
    Socket server = null;
    try
    {
      server = new Socket( "localhost", 3116 );
      Scanner     in  = new Scanner( server.getInputStream() );
      PrintWriter out = new PrintWriter( server.getOutputStream(), true );

      out.println( "2" );
      out.println( "4" );
      System.out.println( in.nextLine() );

      server = new Socket( "localhost", 3116 );
      in  = new Scanner( server.getInputStream() );
      out = new PrintWriter( server.getOutputStream(), true );

      out.println( "23895737895" );
      out.println( "434589358935857" );
      System.out.println( in.nextLine() );
    }
    catch ( UnknownHostException e ) {
      e.printStackTrace();
    }
    catch ( IOException e ) {
      e.printStackTrace();
    }
    finally {
      if ( server != null )
        try { server.close(); } catch ( IOException e ) { }
    }
  }
}

import java.io.*;
import java.math.BigInteger;
import java.net.*;
import java.util.Scanner;

public class MulServer
{
  private static void handleConnection( Socket client ) throws IOException
  {
    Scanner     in  = new Scanner( client.getInputStream() );
    PrintWriter out = new PrintWriter( client.getOutputStream(), true );

    String factor1 = in.nextLine();
    String factor2 = in.nextLine();

    out.println( new BigInteger(factor1).multiply( new BigInteger(factor2) ) );
  }

  public static void main( String[] args ) throws IOException
  {
    ServerSocket server = new ServerSocket( 3116 );

    while ( true )
    {
      Socket client = null;

      try
      {
        client = server.accept();
        handleConnection ( client );
      }
      catch ( IOException e ) {
        e.printStackTrace();
      }
      finally {
        if ( client != null )
          try { client.close(); } catch ( IOException e ) { }
      }
    }
  }
}