In the previous example, we looked
into a connection less java Socket API Program. Now, assume that there are 4
nodes in the distributed system and 100 numbers given as input are to be
processed (for example, checking if a given number is a prime or not). Now we
need a master node to accept this input and proceed with assigning of the work
and again displaying the final output. For simplicity, I am giving input as the
first 100 natural numbers.
The Setup is assumed to consist
of one 5 nodes. One master and others as slaves.
Code: Master.java
import java.net.*;
import java.io.*;
/*
* *************
SOCKET PROGRAMMING (Master) **************
*Author : @NaveenKumar
*Program :To print prime numbers in [1,100]
*Date : 29/10/2013
*File Name :
Master.java
*/
public class Master
{
public static void
main(String args[])
{
int num;
try{
InetAddress[]
receiverHost = {
InetAddress.getByName("127.0.0.1"),
InetAddress.getByName("127.0.0.1"),
InetAddress.getByName("127.0.0.1"),
InetAddress.getByName("127.0.0.1")};
int[]
receiverPort = {3000,3010,3020,3030};
String
message;
//instantiate
a datagram socket for sending the data
DatagramSocket
s = new DatagramSocket();
DatagramSocket
s1 = new DatagramSocket(3500);
byte[]
buffer;
for(int
i=1;i<=100;i++)
{
message
= Integer.toString(i);
buffer
= message.getBytes();
DatagramPacket
p = new
DatagramPacket(buffer,buffer.length,
receiverHost[i%4],receiverPort[i%4]);
s.send(p);
}
s.close();
byte[]
buffer1;
String
msg1;
for(int i =
0;i<100 i="" o:p="">
{
buffer1
= new byte[10];
DatagramPacket
p1 = new DatagramPacket
(buffer1,10);
s1.receive(p1);
msg1 =
new String(buffer1);
//num
= Integer.parseInt(msg1);
if(msg1.charAt(0)!='-')
System.out.println("Received:
"+msg1);
}
s1.close();
}catch(Exception
ex)
{
ex.printStackTrace();
}//end of catch
}//end of main
}//end of class
In
the above program for Master node, a
list of nodes in the network are provided with the port numbers of respective
node on which they are listening. Once the processing of data is done on the
other nodes, then the results are then processed on the Master node and
displayed. If the number -1 is received from any slave, it is ignored but if a
positive integer is received, then it is printed.
Code:
Slave.java
import java.net.*;
import java.io.*;
/*
* ********************
SOCKET PROGRAMMING (SLAVE) **************
* Author : @NaveenKumar
* Date : 29/10/2013
* File Name :
Receiver.java
*/
public class Slave
{
public static void
main(String args[])
{
System.out.println("Starting
Receiver");
if(args.length!=1)
{
System.out.println("Invalid no. of args");
}
else{
int receive_port
= Integer.parseInt(args[0]);
try
{
DatagramSocket
s = new
DatagramSocket(receive_port);
DatagramSocket
soc = new DatagramSocket();
System.out.println("Socket
created");
byte[]
buffer = new byte[10];
System.out.println("buffer
created");
DatagramPacket
p = new DatagramPacket(buffer,10);
System.out.println("packet
created");
int i,j;
i=10;
j=10;
String msg;
Slave sl =
new Slave();
while(i==j)
{
s.receive(p);
msg =
new String(buffer);
//
process the message
sl.process(msg,soc);
}
s.close();
}catch(Exception
ex) // end of try and start of catch
{
ex.printStackTrace();
}// end of catch
}//end of else
}// end of main
public Slave()
{
}
public void
process(String msg, DatagramSocket s1)
{
String
msg1="";
String msg2 =
"";
String message =
msg;
int res = -1;
byte[] buffer;
for(int
k=0;k
{
if((int)message.charAt(k)<58 amp="" nbsp="" span="">
(int)message.charAt(k)>47)
msg2 += message.charAt(k);
else
break;
}
int num =
Integer.parseInt(msg2);
int temp = 0;
for(int
i=1;i
{
if(num%i ==
0)
temp++;
if(temp==2)
break;
}
if(temp==1)
res = num;
else
res = -1;
try{
InetAddress
receiverHost =
InetAddress.getByName("127.0.0.1");
int
receiverPort = 3500;
msg1 =
Integer.toString(res);
System.out.println("Msg:
"+msg1);
buffer =
msg1.getBytes();
DatagramPacket
p1 = new DatagramPacket(buffer,
buffer.length,receiverHost,receiverPort);
s1.send(p1);
}catch(Exception
ex)
{
ex.printStackTrace();
}// end of catch
}//end of process
method
}// end of class Receiver
In
the above code for Slave process, slave process waits for receiving a message
from Master process. Once a number is received, it calls process() method with
the received message as a parameter to this method. Here in this method, the
received data is converted into integer and then checked if it is a prime
number of not. If it is a prime number, the number itself is sent back to the
Master. If it is not a prime number, then -1 is sent back.
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